### Getting Input File Block Start Offset

Source: https://spark.apache.org/docs/latest/api/sql

The `input_file_block_start` function returns the starting offset of the current block being read from an input file. It returns -1 if this information is not available.

```sql
SELECT input_file_block_start();
```

--------------------------------

### Check if String Starts With Substring

Source: https://spark.apache.org/docs/latest/api/sql

Returns a boolean indicating if a string starts with a specified substring. Supports both string and binary types. Returns NULL if either input is NULL.

```sql
SELECT startswith('Spark SQL', 'Spark');
```

```sql
SELECT startswith('Spark SQL', 'SQL');
```

```sql
SELECT startswith('Spark SQL', null);
```

```sql
SELECT startswith(x'537061726b2053514c', x'537061726b');
```

```sql
SELECT startswith(x'537061726b2053514c', x'53514c');
```

--------------------------------

### Get Current Database

Source: https://spark.apache.org/docs/latest/api/sql

Returns the name of the current database in use.

```sql
SELECT current_database();
```

--------------------------------

### ntile Window Function Example

Source: https://spark.apache.org/docs/latest/api/sql

Divides rows into a specified number of buckets within a partition. Useful for distributing data into quantiles.

```sql
SELECT a, b, ntile(2) OVER (PARTITION BY a ORDER BY b) FROM VALUES ('A1', 2), ('A1', 1), ('A2', 3), ('A1', 1) tab(a, b);
```

--------------------------------

### overlay Function Examples

Source: https://spark.apache.org/docs/latest/api/sql

Replaces a portion of a string with another string. Supports both string and byte-based operations.

```sql
SELECT overlay('Spark SQL' PLACING '_' FROM 6);
```

```sql
SELECT overlay('Spark SQL' PLACING 'CORE' FROM 7);
```

```sql
SELECT overlay('Spark SQL' PLACING 'ANSI ' FROM 7 FOR 0);
```

```sql
SELECT overlay('Spark SQL' PLACING 'tructured' FROM 2 FOR 4);
```

```sql
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('_', 'utf-8') FROM 6);
```

```sql
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('CORE', 'utf-8') FROM 7);
```

```sql
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('ANSI ', 'utf-8') FROM 7 FOR 0);
```

```sql
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('tructured', 'utf-8') FROM 2 FOR 4);
```

--------------------------------

### input_file_block_start

Source: https://spark.apache.org/docs/latest/api/sql

Returns the start offset of the current block being read from the input file.

```APIDOC
## input_file_block_start

### Description
Returns the start offset of the block being read, or -1 if not available.

### Method
N/A (SQL Function)

### Endpoint
N/A (SQL Function)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
```sql
SELECT input_file_block_start();
```

### Response
#### Success Response (200)
- **long**: The start offset of the input file block.

#### Response Example
```json
-1
```
```

--------------------------------

### nvl Function Example

Source: https://spark.apache.org/docs/latest/api/sql

Replaces NULL values with a specified alternative. Use this to provide default values for nulls.

```sql
SELECT nvl(NULL, array('2'));
```

--------------------------------

### Find Start Position of Regex Match

Source: https://spark.apache.org/docs/latest/api/sql

Searches a string for a regular expression and returns the 1-based starting position of the first match. Returns 0 if no match is found. Raw string literals are recommended for regex patterns.

```sql
SELECT regexp_instr(r"\abc", r"^\\abc$");
```

```sql
SELECT regexp_instr('user@spark.apache.org', '@[^.]*');
```

--------------------------------

### Get Array Element by Index

Source: https://spark.apache.org/docs/latest/api/sql

Use `get` to retrieve an element from an array at a specific 0-based index. Returns NULL if the index is out of bounds.

```sql
SELECT get(array(1, 2, 3), 0)
```

```sql
SELECT get(array(1, 2, 3), 3)
```

```sql
SELECT get(array(1, 2, 3), -1)
```

--------------------------------

### Get Current Schema

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current database schema name.

```sql
> SELECT current_schema();
 default
```

--------------------------------

### Get Map Keys

Source: https://spark.apache.org/docs/latest/api/sql

Retrieves all keys from a map as an unordered array.

```sql
SELECT map_keys(map(1, 'a', 2, 'b'));
 [1,2]
```

--------------------------------

### nullifzero Function Example

Source: https://spark.apache.org/docs/latest/api/sql

Returns NULL if the expression is zero, otherwise returns the expression itself. Useful for handling zero values as null.

```sql
SELECT nullifzero(0);
```

```sql
SELECT nullifzero(2);
```

--------------------------------

### Get Current Catalog

Source: https://spark.apache.org/docs/latest/api/sql

Returns the name of the current catalog being used.

```sql
SELECT current_catalog();
```

--------------------------------

### instr

Source: https://spark.apache.org/docs/latest/api/sql

Finds the starting index of a substring within a string.

```APIDOC
## instr

### Description
Returns the (1-based) index of the first occurrence of `substr` in `str`.

### Method
N/A (SQL Function)

### Endpoint
N/A (SQL Function)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
```sql
SELECT instr('SparkSQL', 'SQL');
```

### Response
#### Success Response (200)
- **integer**: The 1-based index of the first occurrence of the substring.

#### Response Example
```json
6
```
```

--------------------------------

### parse_url Function Examples

Source: https://spark.apache.org/docs/latest/api/sql

Extracts specific components from a URL. Useful for analyzing or manipulating URL strings.

```sql
SELECT parse_url('http://spark.apache.org/path?query=1', 'HOST');
```

```sql
SELECT parse_url('http://spark.apache.org/path?query=1', 'QUERY');
```

```sql
SELECT parse_url('http://spark.apache.org/path?query=1', 'QUERY', 'query');
```

--------------------------------

### Get Current User

Source: https://spark.apache.org/docs/latest/api/sql

Returns the username of the current execution context.

```sql
> SELECT current_user();
 mockingjay
```

--------------------------------

### date_add

Source: https://spark.apache.org/docs/latest/api/sql

Returns the date that is a specified number of days after a start date.

```APIDOC
## date_add

### Description
Returns the date that is `num_days` after `start_date`.

### Syntax
`date_add(start_date, num_days)`

### Arguments
* `start_date` - The starting date.
* `num_days` - The number of days to add.

### Examples
```sql
> SELECT date_add('2016-07-30', 1);
 2016-07-31
```

### Since
1.5.0
```

--------------------------------

### nvl2 Function Example

Source: https://spark.apache.org/docs/latest/api/sql

Returns one of two expressions based on whether the first expression is NULL or not. Use for conditional value selection.

```sql
SELECT nvl2(NULL, 2, 1);
```

--------------------------------

### overlay

Source: https://spark.apache.org/docs/latest/api/sql

Replaces a portion of a string with another string, starting at a specified position and length.

```APIDOC
## overlay

### Description
Replaces `input` with `replace` that starts at `pos` and is of length `len`.

### Arguments
* **input** - The original string.
* **replace** - The string to insert.
* **pos** - The starting position for the replacement.
* **len** - Optional. The length of the substring to replace.

### Example
```sql
SELECT overlay('Spark SQL' PLACING '_' FROM 6)
SELECT overlay('Spark SQL' PLACING 'CORE' FROM 7)
SELECT overlay('Spark SQL' PLACING 'ANSI ' FROM 7 FOR 0)
SELECT overlay('Spark SQL' PLACING 'tructured' FROM 2 FOR 4)
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('_', 'utf-8') FROM 6)
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('CORE', 'utf-8') FROM 7)
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('ANSI ', 'utf-8') FROM 7 FOR 0)
SELECT overlay(encode('Spark SQL', 'utf-8') PLACING encode('tructured', 'utf-8') FROM 2 FOR 4)
```
```

--------------------------------

### nullif Function Example

Source: https://spark.apache.org/docs/latest/api/sql

Returns NULL if two expressions are equal, otherwise returns the first expression. Use for conditional null assignment.

```sql
SELECT nullif(2, 2);
```

--------------------------------

### Get Current Timestamp

Source: https://spark.apache.org/docs/latest/api/sql

Retrieves the current timestamp at the start of query evaluation. All calls within the same query return the same value.

```sql
> SELECT current_timestamp();
 2020-04-25 15:49:11.914
```

```sql
> SELECT current_timestamp;
 2020-04-25 15:49:11.914
```

--------------------------------

### startswith

Source: https://spark.apache.org/docs/latest/api/sql

Checks if a string or binary value begins with a specified prefix. Returns true if it does, false otherwise, and NULL if either input is NULL.

```APIDOC
## startswith

### Description
Checks if a string or binary value begins with a specified prefix. Returns true if it does, false otherwise, and NULL if either input is NULL.

### Method
SQL Function

### Signature
startswith(left, right)

### Arguments
* **left** (STRING or BINARY) - The value to check.
* **right** (STRING or BINARY) - The prefix to check for.

### Examples
```sql
> SELECT startswith('Spark SQL', 'Spark');
true
> SELECT startswith('Spark SQL', 'SQL');
false
> SELECT startswith('Spark SQL', null);
NULL
> SELECT startswith(x'537061726b2053514c', x'537061726b');
true
> SELECT startswith(x'537061726b2053514c', x'53514c');
false
```

### Since
3.3.0
```

--------------------------------

### Convert to Protobuf with to_protobuf

Source: https://spark.apache.org/docs/latest/api/sql

Converts Catalyst binary input to Protobuf format. Requires message name, descriptor file path, and optional options.

```sql
SELECT to_protobuf(s, 'Person', '/path/to/descriptor.desc', map('emitDefaultValues', 'true')) IS NULL FROM (SELECT NULL AS s);
```

--------------------------------

### Get Current Date

Source: https://spark.apache.org/docs/latest/api/sql

Retrieves the current date at the start of query evaluation. All calls within the same query return the same value.

```sql
> SELECT current_date();
 2020-04-25
```

```sql
> SELECT current_date;
 2020-04-25
```

--------------------------------

### time_diff(unit, start, end)

Source: https://spark.apache.org/docs/latest/api/sql

Gets the difference between two times in the specified units (HOUR, MINUTE, SECOND, MILLISECOND, MICROSECOND).

```APIDOC
## time_diff(unit, start, end)

### Description
Gets the difference between two times in the specified units.

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
- **result** (bigint) - The difference between the start and end times in the specified unit.

### Response Example
```sql
> SELECT time_diff('HOUR', TIME'20:30:29', TIME'21:30:28');
 0
> SELECT time_diff('HOUR', TIME'20:30:29', TIME'21:30:29');
 1
> SELECT time_diff('HOUR', TIME'20:30:29', TIME'12:00:00');
 -8
```
```

--------------------------------

### Format String with Placeholders

Source: https://spark.apache.org/docs/latest/api/sql

Use `format_string` to create formatted strings using printf-style format specifiers.

```sql
SELECT format_string("Hello World %d %s", 100, "days");
```

--------------------------------

### Get Current Local Timestamp

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current timestamp without time zone at the start of query evaluation. All calls within the same query return the same value.

```sql
> SELECT localtimestamp();
 2020-04-25 15:49:11.914
```

--------------------------------

### Convert Protobuf to Catalyst Value

Source: https://spark.apache.org/docs/latest/api/sql

Use `from_protobuf` to convert binary Protobuf data into a Catalyst value. Ensure the Protobuf schema matches the data; otherwise, behavior is undefined. Schema evolution can be handled via options.

```sql
SELECT from_protobuf(s, 'Person', '/path/to/descriptor.desc', map()) IS NULL AS result FROM (SELECT NAMED_STRUCT('name', name, 'id', id) AS s FROM VALUES ('John Doe', 1), (NULL,  2) tab(name, id))
```

--------------------------------

### Get Current Time

Source: https://spark.apache.org/docs/latest/api/sql

Retrieves the current time at the start of query evaluation, with optional precision for fractional seconds. All calls within the same query return the same value.

```sql
> SELECT current_time();
 15:49:11.914120
```

```sql
> SELECT current_time;
 15:49:11.914120
```

```sql
> SELECT current_time(0);
 15:49:11
```

```sql
> SELECT current_time(3);
 15:49:11.914
```

```sql
> SELECT current_time(1+1);
 15:49:11.91
```

--------------------------------

### Get Week of Year

Source: https://spark.apache.org/docs/latest/api/sql

Calculates the week of the year for a given date. A week starts on Monday, and week 1 is the first week with more than three days. Useful for temporal aggregations.

```sql
SELECT weekofyear('2008-02-20');
```

--------------------------------

### percent_rank Window Function Example

Source: https://spark.apache.org/docs/latest/api/sql

Computes the percentage rank of a value within its partition. Use this to understand a value's relative position in a sorted dataset.

```sql
SELECT a, b, percent_rank(b) OVER (PARTITION BY a ORDER BY b) FROM VALUES ('A1', 2), ('A1', 1), ('A2', 3), ('A1', 1) tab(a, b);
```

--------------------------------

### Find Next Day of Week

Source: https://spark.apache.org/docs/latest/api/sql

Returns the first date that is later than the start date and matches the specified day of the week.

```sql
> SELECT next_day('2015-01-14', 'TU');
 2015-01-20
```

--------------------------------

### locate

Source: https://spark.apache.org/docs/latest/api/sql

Returns the position of the first occurrence of a substring within a string, optionally starting from a specified position. Both the starting position and the return value are 1-based.

```APIDOC
## locate

### Description
Returns the position of the first occurrence of `substr` in `str` after position `pos`. The given `pos` and return value are 1-based.

### Syntax
`locate(substr, str[, pos])`

### Parameters
* `substr` (string) - The substring to search for.
* `str` (string) - The string to search within.
* `pos` (integer, optional) - The 1-based position to start the search from.

### Examples
```sql
SELECT locate('bar', 'foobarbar');
-- Result: 4

SELECT locate('bar', 'foobarbar', 5);
-- Result: 7

SELECT POSITION('bar' IN 'foobarbar');
-- Result: 4
```

**Since:** 1.5.0
```

--------------------------------

### Create time from hour, minute, and second

Source: https://spark.apache.org/docs/latest/api/sql

Constructs a time value from hour, minute, and second components. Throws an error for invalid inputs.

```SQL
SELECT make_time(6, 30, 45.887);
 06:30:45.887
```

```SQL
SELECT make_time(NULL, 30, 0);
 NULL
```

--------------------------------

### dateadd

Source: https://spark.apache.org/docs/latest/api/sql

Calculates a future date by adding a specified number of days to a start date. The function takes the start date and the number of days to add as arguments.

```APIDOC
## dateadd(start_date, num_days)

### Description
Returns the date that is `num_days` after `start_date`.

### Arguments
* `start_date` - The starting date.
* `num_days` - The number of days to add.

### Examples:
```
> SELECT dateadd('2016-07-30', 1);
 2016-07-31
```

**Since:** 3.4.0
```

--------------------------------

### octet_length Function Examples

Source: https://spark.apache.org/docs/latest/api/sql

Calculates the byte length of a string or binary data. Useful for determining storage size or data transfer size.

```sql
SELECT octet_length('Spark SQL');
```

```sql
SELECT octet_length(x'537061726b2053514c');
```

--------------------------------

### Mask String with Default Characters (Example 2)

Source: https://spark.apache.org/docs/latest/api/sql

Demonstrates default string masking behavior where uppercase letters become 'X', lowercase 'x', and digits 'n'.

```sql
SELECT mask('AbCD123-@$#');
```

--------------------------------

### Array Slicing

Source: https://spark.apache.org/docs/latest/api/sql

Extracts a sub-array from a given array. Supports positive and negative start indices, with indices starting at 1. Negative indices count from the end of the array.

```sql
SELECT slice(array(1, 2, 3, 4), 2, 2);
 [2,3]
```

```sql
SELECT slice(array(1, 2, 3, 4), -2, 2);
 [3,4]
```

--------------------------------

### Create Map from Entries

Source: https://spark.apache.org/docs/latest/api/sql

Builds a map from an array of key-value entry structs.

```sql
SELECT map_from_entries(array(struct(1, 'a'), struct(2, 'b')));
 {1:"a",2:"b"}
```

--------------------------------

### Logical OR Operator Example

Source: https://spark.apache.org/docs/latest/api/sql

Performs a logical OR operation. Returns true if either operand is true, and handles NULLs according to standard SQL logic.

```sql
SELECT true or false;
```

```sql
SELECT false or false;
```

```sql
SELECT true or NULL;
```

```sql
SELECT false or NULL;
```

--------------------------------

### Create Map from Arrays

Source: https://spark.apache.org/docs/latest/api/sql

Constructs a map by pairing elements from a key array and a value array. Keys must not be null.

```sql
SELECT map_from_arrays(array(1.0, 3.0), array('2', '4'));
 {1.0:"2",3.0:"4"}
```

--------------------------------

### inline

Source: https://spark.apache.org/docs/latest/api/sql

Explodes an array of structs into a table with default column names.

```APIDOC
## inline

### Description
Explodes an array of structs into a table. Uses column names col1, col2, etc. by default unless specified otherwise.

### Method
N/A (SQL Function)

### Endpoint
N/A (SQL Function)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
```sql
SELECT * FROM inline(array(struct(1, 'a'), struct(2, 'b')));
```

### Response
#### Success Response (200)
- **table**: A table with columns col1, col2, etc. representing the exploded structs.

#### Response Example
```json
[
  {"col1": 1, "col2": "a"},
  {"col1": 2, "col2": "b"}
]
```
```

--------------------------------

### Format string with printf

Source: https://spark.apache.org/docs/latest/api/sql

Returns a formatted string using printf-style format specifiers. Supports integers and strings.

```sql
SELECT printf("Hello World %d %s", 100, "days");
 Hello World 100 days
```

--------------------------------

### Get Map Values

Source: https://spark.apache.org/docs/latest/api/sql

Retrieves all values from a map as an unordered array.

```sql
SELECT map_values(map(1, 'a', 2, 'b'));
 ["a","b"]
```

--------------------------------

### Get Day of Month

Source: https://spark.apache.org/docs/latest/api/sql

Returns the day of the month from a date or timestamp.

```sql
SELECT day('2009-07-30');
 30
```

--------------------------------

### to_protobuf

Source: https://spark.apache.org/docs/latest/api/sql

Converts a Catalyst binary input value into its corresponding Protobuf format result using a descriptor file.

```APIDOC
## to_protobuf

### Description
Converts a Catalyst binary input value into its corresponding Protobuf format result.

### Arguments
* **child** (binary) - The Catalyst binary input value.
* **messageName** (string) - The name of the Protobuf message.
* **descFilePath** (string) - The path to the descriptor file.
* **options** (map<string, string>) - Optional. A map of options.

### Examples
```sql
> SELECT to_protobuf(s, 'Person', '/path/to/descriptor.desc', map('emitDefaultValues', 'true')) IS NULL FROM (SELECT NULL AS s);
 [true]
```

**Since:** 4.0.0
```

--------------------------------

### Estimate Top K Items with approx_top_k_estimate

Source: https://spark.apache.org/docs/latest/api/sql

Returns the top k items with their frequency from a sketch. The k parameter is optional and defaults to 5. Ensure the input sketch is created using approx_top_k_accumulate.

```sql
SELECT approx_top_k_estimate(approx_top_k_accumulate(expr)) FROM VALUES (0), (0), (1), (1), (2), (3), (4), (4) AS tab(expr);

```

```sql
SELECT approx_top_k_estimate(approx_top_k_accumulate(expr), 2) FROM VALUES 'a', 'b', 'c', 'c', 'c', 'c', 'd', 'd' tab(expr);

```

--------------------------------

### Safe binary conversion with try_to_binary

Source: https://spark.apache.org/docs/latest/api/sql

Converts a string to binary using a specified encoding. Returns NULL if the conversion fails or the format is invalid.

```sql
SELECT try_to_binary('abc', 'utf-8');
```

```sql
select try_to_binary('a!', 'base64');
```

```sql
select try_to_binary('abc', 'invalidFormat');
```

--------------------------------

### base64

Source: https://spark.apache.org/docs/latest/api/sql

Converts the argument from a binary `bin` to a base 64 string.

```APIDOC
## base64

### Description
Converts the argument from a binary `bin` to a base 64 string.

### Syntax
`base64(bin)`

### Parameters
* `bin` - The binary data to convert.

### Examples
```sql
SELECT base64('Spark SQL');
-- Output: U3BhcmsgU1FM

SELECT base64(x'537061726b2053514c');
-- Output: U3BhcmsgU1FM
```
```

--------------------------------

### date_sub

Source: https://spark.apache.org/docs/latest/api/sql

Returns the date that is a specified number of days before a start date.

```APIDOC
## date_sub

### Description
Returns the date that is `num_days` before `start_date`.

### Syntax
`date_sub(start_date, num_days)`

### Arguments
* `start_date` - The starting date.
* `num_days` - The number of days to subtract.

### Examples
```sql
> SELECT date_sub('2016-07-30', 1);
 2016-07-29
```

### Since
1.5.0
```

--------------------------------

### array

Source: https://spark.apache.org/docs/latest/api/sql

Creates an array with the provided elements.

```APIDOC
## array

### Description
Returns an array with the given elements.

### Method
N/A (SQL Function)

### Endpoint
N/A (SQL Function)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
```sql
SELECT array(1, 2, 3);
```

### Response
#### Success Response (200)
N/A (SQL Function Result)

#### Response Example
```json
[1,2,3]
```

**Since:** 1.1.0
```

--------------------------------

### printf

Source: https://spark.apache.org/docs/latest/api/sql

Returns a formatted string based on a printf-style format string and provided arguments.

```APIDOC
## printf

### Description
Returns a formatted string from printf-style format strings.

### Syntax
printf(strfmt, obj, ...)

### Parameters
* **strfmt** (string) - The format string.
* **obj, ...** (any) - The arguments to format.

### Examples
```sql
> SELECT printf("Hello World %d %s", 100, "days");
 Hello World 100 days
```
```

--------------------------------

### Get the value of Pi

Source: https://spark.apache.org/docs/latest/api/sql

The pi() function returns the mathematical constant pi.

```sql
SELECT pi();
```

--------------------------------

### Get Current Timestamp

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current timestamp at the beginning of the query evaluation.

```sql
> SELECT now();
 2020-04-25 15:49:11.914
```

--------------------------------

### Create Date from Unix Date

Source: https://spark.apache.org/docs/latest/api/sql

Constructs a date from the number of days since January 1, 1970.

```sql
> SELECT date_from_unix_date(1);
 1970-01-02
```

--------------------------------

### Get Map Entries

Source: https://spark.apache.org/docs/latest/api/sql

Extracts all key-value pairs from a map as an array of structs.

```sql
SELECT map_entries(map(1, 'a', 2, 'b'));
 [{"key":1,"value":"a"},{"key":2,"value":"b"}]
```

--------------------------------

### Find approximate top K items

Source: https://spark.apache.org/docs/latest/api/sql

Returns the top K items and their frequencies using an approximate algorithm. Parameters for K and max items tracked can be specified.

```sql
SELECT approx_top_k(expr) FROM VALUES (0), (0), (1), (1), (2), (3), (4), (4) AS tab(expr);

```

```sql
SELECT approx_top_k(expr, 2) FROM VALUES 'a', 'b', 'c', 'c', 'c', 'c', 'd', 'd' AS tab(expr);

```

```sql
SELECT approx_top_k(expr, 10, 100) FROM VALUES (0), (1), (1), (2), (2), (2) AS tab(expr);

```

--------------------------------

### Get Day of Year

Source: https://spark.apache.org/docs/latest/api/sql

Returns the day of the year for a given date or timestamp.

```sql
SELECT dayofyear('2016-04-09');
 100
```

--------------------------------

### Get Current Timezone

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current session's local timezone.

```sql
> SELECT current_timezone();
 Asia/Shanghai
```

--------------------------------

### Combine Sketches with approx_top_k_combine

Source: https://spark.apache.org/docs/latest/api/sql

Combines multiple sketches into a single sketch. The maxItemsTracked parameter is optional and sets the limit for the combined sketch. If not specified, input sketches must have the same maxItemsTracked value.

```sql
SELECT approx_top_k_estimate(approx_top_k_combine(sketch, 10000), 5) FROM (SELECT approx_top_k_accumulate(expr) AS sketch FROM VALUES (0), (0), (1), (1) AS tab(expr) UNION ALL SELECT approx_top_k_accumulate(expr) AS sketch FROM VALUES (2), (3), (4), (4) AS tab(expr));

```

--------------------------------

### weekofyear

Source: https://spark.apache.org/docs/latest/api/sql

Returns the week of the year for a given date, where weeks start on Monday.

```APIDOC
## weekofyear weekofyear(date)

### Description
Returns the week of the year of the given date. A week is considered to start on a Monday and week 1 is the first week with >3 days.

### Examples
```sql
> SELECT weekofyear('2008-02-20');
 8
```
```

--------------------------------

### Create Map from String

Source: https://spark.apache.org/docs/latest/api/sql

Creates a map by splitting a string using specified or default delimiters. Available since version 2.0.1.

```sql
SELECT str_to_map('a:1,b:2,c:3', ',', ':');
```

```sql
SELECT str_to_map('a');
```

--------------------------------

### ntile

Source: https://spark.apache.org/docs/latest/api/sql

Divides the rows within each window partition into a specified number of buckets, ranging from 1 to n.

```APIDOC
## ntile

### Description
Divides the rows for each window partition into `n` buckets ranging from 1 to at most `n`.

### Arguments
* **buckets** - An integer expression specifying the number of buckets. Defaults to 1.

### Example
```sql
SELECT a, b, ntile(2) OVER (PARTITION BY a ORDER BY b) FROM VALUES ('A1', 2), ('A1', 1), ('A2', 3), ('A1', 1) tab(a, b)
```
```

--------------------------------

### make_time

Source: https://spark.apache.org/docs/latest/api/sql

Creates a time value from hour, minute, and second components. Throws an error for invalid inputs.

```APIDOC
## make_time

### Description
Create time from hour, minute and second fields. For invalid inputs it will throw an error.

### Syntax
`make_time(hour, minute, second)`

### Parameters
* `hour` (integer) - The hour to represent, from 0 to 23.
* `minute` (integer) - The minute to represent, from 0 to 59.
* `second` (double) - The second to represent, from 0 to 59.999999.

### Examples
```sql
SELECT make_time(6, 30, 45.887);
-- Result: 06:30:45.887

SELECT make_time(NULL, 30, 0);
-- Result: NULL
```

**Since:** 4.1.0
```

--------------------------------

### Convert KLL Sketch to String (Float)

Source: https://spark.apache.org/docs/latest/api/sql

Returns a human-readable summary of a KLL sketch. Useful for debugging or inspecting sketch contents.

```sql
SELECT LENGTH(kll_sketch_to_string_float(kll_sketch_agg_float(col))) > 0 FROM VALUES (CAST(1.0 AS FLOAT)), (CAST(2.0 AS FLOAT)), (CAST(3.0 AS FLOAT)), (CAST(4.0 AS FLOAT)), (CAST(5.0 AS FLOAT)) tab(col);
```

--------------------------------

### Add Days to a Date

Source: https://spark.apache.org/docs/latest/api/sql

Calculates the date that is a specified number of days after a start date.

```sql
SELECT dateadd('2016-07-30', 1);
 2016-07-31
```

--------------------------------

### Calculate Date Difference

Source: https://spark.apache.org/docs/latest/api/sql

Computes the number of days between an end date and a start date.

```sql
> SELECT date_diff('2009-07-31', '2009-07-30');
 1
```

```sql
> SELECT date_diff('2009-07-30', '2009-07-31');
 -1
```

--------------------------------

### Convert String to Binary

Source: https://spark.apache.org/docs/latest/api/sql

Converts an input string to a binary value using a specified format (hex, utf-8, base64). Defaults to hex if no format is provided. Returns NULL if any input is NULL.

```sql
SELECT to_binary('abc', 'utf-8');
 abc
```

--------------------------------

### Get Month Name from Date

Source: https://spark.apache.org/docs/latest/api/sql

Returns the three-letter abbreviated month name from a given date.

```sql
> SELECT monthname('2008-02-20');
 Feb
```

--------------------------------

### Create Year-Month Interval

Source: https://spark.apache.org/docs/latest/api/sql

Constructs a year-month interval from specified years and months. Handles positive and negative values.

```sql
SELECT make_ym_interval(1, 2);
 1-2
> SELECT make_ym_interval(1, 0);
 1-0
> SELECT make_ym_interval(-1, 1);
 -0-11
> SELECT make_ym_interval(2);
 2-0
```

--------------------------------

### Get Count from Float KLL Sketch

Source: https://spark.apache.org/docs/latest/api/sql

Returns the number of items that have been added to the KLL sketch.

```sql
SELECT kll_sketch_get_n_float(kll_sketch_agg_float(col)) FROM VALUES (CAST(1.0 AS FLOAT)), (CAST(2.0 AS FLOAT)), (CAST(3.0 AS FLOAT)), (CAST(4.0 AS FLOAT)), (CAST(5.0 AS FLOAT)) tab(col);
```

--------------------------------

### Get Count from Double KLL Sketch

Source: https://spark.apache.org/docs/latest/api/sql

Returns the count of elements aggregated into the KLL sketch.

```sql
SELECT kll_sketch_get_n_double(kll_sketch_agg_double(col)) FROM VALUES (CAST(1.0 AS DOUBLE)), (CAST(2.0 AS DOUBLE)), (CAST(3.0 AS DOUBLE)), (CAST(4.0 AS DOUBLE)), (CAST(5.0 AS DOUBLE)) tab(col);
```

--------------------------------

### from_protobuf

Source: https://spark.apache.org/docs/latest/api/sql

Converts a binary Protobuf value into a Catalyst value. Ensure the provided Protobuf schema matches the data schema for predictable results.

```APIDOC
## from_protobuf(data, messageName, descFilePath, options)

### Description
Converts a binary Protobuf value into a Catalyst value.

### Parameters
- **data**: The binary Protobuf data.
- **messageName**: The name of the Protobuf message.
- **descFilePath**: The path to the Protobuf descriptor file.
- **options**: Optional configuration map.

### Request Example
```sql
SELECT from_protobuf(s, 'Person', '/path/to/descriptor.desc', map()) IS NULL AS result FROM (SELECT NAMED_STRUCT('name', name, 'id', id) AS s FROM VALUES ('John Doe', 1), (NULL,  2) tab(name, id))
```

### Response
- **result**: Boolean indicating if the conversion resulted in NULL.
```

--------------------------------

### get

Source: https://spark.apache.org/docs/latest/api/sql

Retrieves an element from an array at a specified zero-based index. Returns NULL if the index is out of bounds.

```APIDOC
## get(array, index)

### Description
Returns element of array at given (0-based) index. If the index points outside of the array boundaries, then this function returns NULL.

### Arguments
- **array**: The input array.
- **index**: The zero-based index of the element to retrieve.

### Examples
```sql
> SELECT get(array(1, 2, 3), 0);
 1
> SELECT get(array(1, 2, 3), 3);
 NULL
> SELECT get(array(1, 2, 3), -1);
 NULL
```
```

--------------------------------

### Get Euler's Number

Source: https://spark.apache.org/docs/latest/api/sql

Returns the mathematical constant e, the base of the natural logarithm.

```sql
SELECT e();
 2.718281828459045
```

--------------------------------

### initcap

Source: https://spark.apache.org/docs/latest/api/sql

Converts a string so that the first letter of each word is capitalized and the rest are lowercase.

```APIDOC
## initcap

### Description
Returns `str` with the first letter of each word in uppercase. All other letters are in lowercase. Words are delimited by white space.

### Method
N/A (SQL Function)

### Endpoint
N/A (SQL Function)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
```sql
SELECT initcap('sPark sql');
```

### Response
#### Success Response (200)
- **string**: The input string with words capitalized.

#### Response Example
```json
"Spark Sql"
```
```

--------------------------------

### Get Day of Week

Source: https://spark.apache.org/docs/latest/api/sql

Returns the day of the week for a date/timestamp, where 1 is Sunday and 7 is Saturday.

```sql
SELECT dayofweek('2009-07-30');
 5
```

--------------------------------

### from_avro

Source: https://spark.apache.org/docs/latest/api/sql

Converts a binary Avro value into a Catalyst value using a provided JSON schema.

```APIDOC
## from_avro

### Description
Converts a binary Avro value into a Catalyst value.

### Parameters
- **child**: The binary Avro data.
- **jsonFormatSchema**: The JSON schema for the Avro data.
- **options**: A map of options for deserialization.

### Examples
```sql
SELECT from_avro(s, '{"type": "record", "name": "struct", "fields": [{ "name": "u", "type": ["int","string"] }]}', map()) IS NULL AS result FROM (SELECT NAMED_STRUCT('u', NAMED_STRUCT('member0', member0, 'member1', member1)) AS s FROM VALUES (1, NULL), (NULL,  'a') tab(member0, member1));
-- Result: [false]
```

### Note
The specified schema must match the actual schema of the read data. Use options to specify an evolved schema.
```

--------------------------------

### Get Abbreviated Day Name

Source: https://spark.apache.org/docs/latest/api/sql

Returns the three-letter abbreviated day name for a given date.

```sql
SELECT dayname(DATE('2008-02-20'));
 Wed
```

--------------------------------

### Return First Non-Null Argument

Source: https://spark.apache.org/docs/latest/api/sql

Returns the first non-null argument provided. If all arguments are null, it returns null.

```sql
> SELECT coalesce(NULL, 1, NULL);
 1
```

--------------------------------

### current_time

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current time at the start of query evaluation, with optional precision for fractional seconds.

```APIDOC
## current_time

### Description
Returns the current time at the start of query evaluation. All calls of `current_time` within the same query return the same value.

### Syntax
`current_time([precision])`
`current_time`

### Arguments
* `precision` - An optional integer literal in the range [0..6], indicating how many fractional digits of seconds to include. If omitted, the default is 6.

### Examples
```sql
> SELECT current_time();
 15:49:11.914120
> SELECT current_time;
 15:49:11.914120
> SELECT current_time(0);
 15:49:11
> SELECT current_time(3);
 15:49:11.914
> SELECT current_time(1+1);
 15:49:11.91
```

### Since
4.1.0
```

--------------------------------

### Mask NULL Input with Default Settings

Source: https://spark.apache.org/docs/latest/api/sql

Shows that passing NULL as input to the mask function results in a NULL output, regardless of other parameters.

```sql
SELECT mask(NULL);
```

--------------------------------

### Generate Count-Min Sketch

Source: https://spark.apache.org/docs/latest/api/sql

Creates a Count-Min Sketch for cardinality estimation. The result is a byte array that needs deserialization for use.

```sql
SELECT hex(count_min_sketch(col, 0.5d, 0.5d, 1)) FROM VALUES (1), (2), (1) AS tab(col);
```

--------------------------------

### Subtract Days from Date

Source: https://spark.apache.org/docs/latest/api/sql

Calculates a date by subtracting a specified number of days from a start date.

```sql
> SELECT date_sub('2016-07-30', 1);
 2016-07-29
```

--------------------------------

### Add Days to Date

Source: https://spark.apache.org/docs/latest/api/sql

Calculates a date by adding a specified number of days to a start date.

```sql
> SELECT date_add('2016-07-30', 1);
 2016-07-31
```

--------------------------------

### make_date

Source: https://spark.apache.org/docs/latest/api/sql

Constructs a date value from year, month, and day components. Throws an error on invalid input if ANSI SQL is enabled, otherwise returns NULL.

```APIDOC
## make_date

### Description
Create date from year, month and day fields. If the configuration `spark.sql.ansi.enabled` is false, the function returns NULL on invalid inputs. Otherwise, it will throw an error instead.

### Syntax
`make_date(year, month, day)`

### Parameters
* `year` (integer) - The year to represent, from 1 to 9999.
* `month` (integer) - The month-of-year to represent, from 1 (January) to 12 (December).
* `day` (integer) - The day-of-month to represent, from 1 to 31.

### Examples
```sql
SELECT make_date(2013, 7, 15);
-- Result: 2013-07-15

SELECT make_date(2019, 7, NULL);
-- Result: NULL
```

**Since:** 3.0.0
```

--------------------------------

### Get Day of Month (Alternative)

Source: https://spark.apache.org/docs/latest/api/sql

Returns the day of the month from a date or timestamp. This is an alias for the 'day' function.

```sql
SELECT dayofmonth('2009-07-30');
 30
```

--------------------------------

### Format Binary Data to String

Source: https://spark.apache.org/docs/latest/api/sql

Converts binary data to a string representation using 'base64', 'hex', or 'utf-8' encoding.

```sql
SELECT to_varchar(x'537061726b2053514c', 'base64');
```

```sql
SELECT to_varchar(x'537061726b2053514c', 'hex');
```

```sql
SELECT to_varchar(encode('abc', 'utf-8'), 'utf-8');
```

--------------------------------

### Create Geometry from WKB

Source: https://spark.apache.org/docs/latest/api/sql

Parses a Well-Known Binary (WKB) string and returns the corresponding GEOMETRY value. Used for deserializing geospatial data.

```sql
SELECT hex(st_asbinary(st_geomfromwkb(X'0101000000000000000000F03F0000000000000040')));
```

--------------------------------

### Get Size of Array

Source: https://spark.apache.org/docs/latest/api/sql

Returns the number of elements in an array. Returns null if the input array is null.

```sql
SELECT array_size(array('b', 'd', 'c', 'a'));
 4
```

--------------------------------

### Get any value from a group

Source: https://spark.apache.org/docs/latest/api/sql

Returns an arbitrary value from a group of rows. Can be configured to ignore NULL values.

```sql
SELECT any_value(col) FROM VALUES (10), (5), (20) AS tab(col);

```

```sql
SELECT any_value(col) FROM VALUES (NULL), (5), (20) AS tab(col);

```

```sql
SELECT any_value(col, true) FROM VALUES (NULL), (5), (20) AS tab(col);

```

--------------------------------

### Generate Session Windows for Streaming Data

Source: https://spark.apache.org/docs/latest/api/sql

Creates session windows based on a timestamp column and a gap duration. Handles both fixed and dynamic gap durations.

```sql
SELECT a, session_window.start, session_window.end, count(*) as cnt FROM VALUES ('A1', '2021-01-01 00:00:00'), ('A1', '2021-01-01 00:04:30'), ('A1', '2021-01-01 00:10:00'), ('A2', '2021-01-01 00:01:00') AS tab(a, b) GROUP by a, session_window(b, '5 minutes') ORDER BY a, start;
  A1    2021-01-01 00:00:00 2021-01-01 00:09:30 2
  A1    2021-01-01 00:10:00 2021-01-01 00:15:00 1
  A2    2021-01-01 00:01:00 2021-01-01 00:06:00 1
```

```sql
SELECT a, session_window.start, session_window.end, count(*) as cnt FROM VALUES ('A1', '2021-01-01 00:00:00'), ('A1', '2021-01-01 00:04:30'), ('A1', '2021-01-01 00:10:00'), ('A2', '2021-01-01 00:01:00'), ('A2', '2021-01-01 00:04:30') AS tab(a, b) GROUP by a, session_window(b, CASE WHEN a = 'A1' THEN '5 minutes' WHEN a = 'A2' THEN '1 minute' ELSE '10 minutes' END) ORDER BY a, start;
  A1    2021-01-01 00:00:00 2021-01-01 00:09:30 2
  A1    2021-01-01 00:10:00 2021-01-01 00:15:00 1
  A2    2021-01-01 00:01:00 2021-01-01 00:02:00 1
  A2    2021-01-01 00:04:30 2021-01-01 00:05:30 1
```

--------------------------------

### next_day

Source: https://spark.apache.org/docs/latest/api/sql

Finds the first date that is later than a given start date and falls on a specified day of the week.

```APIDOC
## next_day

### Description
Returns the first date which is later than `start_date` and named as indicated. The function returns NULL if at least one of the input parameters is NULL. When both of the input parameters are not NULL and `day_of_week` is an invalid input, the function throws SparkIllegalArgumentException if `spark.sql.ansi.enabled` is set to true, otherwise NULL.

### Method
next_day(start_date, day_of_week)

### Parameters
- **start_date** (date) - The date from which to find the next day of the week.
- **day_of_week** (string) - The target day of the week (e.g., 'TU' for Tuesday).

### Examples
```
> SELECT next_day('2015-01-14', 'TU');
 2015-01-20
```
```

--------------------------------

### Create Map from Key-Value Pairs

Source: https://spark.apache.org/docs/latest/api/sql

Generates a map data structure from a list of key-value pairs.

```sql
SELECT map(1.0, '2', 3.0, '4');
 {1.0:"2",3.0:"4"}
```

--------------------------------

### current_timestamp

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current timestamp at the start of query evaluation. All calls within the same query return the same value.

```APIDOC
## current_timestamp

### Description
Returns the current timestamp at the start of query evaluation. All calls of `current_timestamp` within the same query return the same value.

### Syntax
`current_timestamp()`
`current_timestamp`

### Examples
```sql
> SELECT current_timestamp();
 2020-04-25 15:49:11.914
> SELECT current_timestamp;
 2020-04-25 15:49:11.914
```

### Notes
The syntax without braces has been supported since 2.0.1.

### Since
1.5.0
```

--------------------------------

### current_date

Source: https://spark.apache.org/docs/latest/api/sql

Returns the current date at the start of query evaluation. All calls within the same query return the same value.

```APIDOC
## current_date

### Description
Returns the current date at the start of query evaluation. All calls of `current_date` within the same query return the same value.

### Syntax
`current_date()`
`current_date`

### Examples
```sql
> SELECT current_date();
 2020-04-25
> SELECT current_date;
 2020-04-25
```

### Notes
The syntax without braces has been supported since 2.0.1.

### Since
1.5.0
```

--------------------------------

### Repeat Element to Create Array

Source: https://spark.apache.org/docs/latest/api/sql

Creates an array by repeating a given element a specified number of times.

```sql
SELECT array_repeat('123', 2);
 ["123","123"]
```

--------------------------------

### format_string

Source: https://spark.apache.org/docs/latest/api/sql

Returns a formatted string using printf-style format specifiers.

```APIDOC
## format_string

### Description
Returns a formatted string from printf-style format strings.

### Parameters
- **strfmt**: The format string.
- **obj, ...**: The objects to format.

### Examples
```sql
SELECT format_string("Hello World %d %s", 100, "days");
-- Result: Hello World 100 days
```
```

--------------------------------

### Prepend Element to Array

Source: https://spark.apache.org/docs/latest/api/sql

Adds an element to the beginning of an array. The element type must match the array's element type. Handles null elements and null arrays.

```sql
SELECT array_prepend(array('b', 'd', 'c', 'a'), 'd');
 ["d","b","d","c","a"]
```

```sql
SELECT array_prepend(array(1, 2, 3, null), null);
 [null,1,2,3,null]
```

```sql
SELECT array_prepend(CAST(null as Array<Int>), 2);
 NULL
```