### Query ClickHouse with basic SELECT

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Executes a SQL query against the ClickHouse database and retrieves the results. This example selects specific columns from the 'mtcars' table based on a condition.

```R
dbGetQuery(con, "SELECT car, mpg, cyl, hp FROM mtcars WHERE hp>=110")
```

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

### Get ClickHouse Connection Information

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Retrieves general information about the ClickHouse database connection.

```R
dbGetInfo(dbObj, ...)
```

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

### Create and use an alternative database

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Demonstrates how to create a new database in ClickHouse and then switch the active database for subsequent operations within the current session. The `dbname` argument in `dbConnect` can also pre-select a database.

```R
dbSendQuery(con, "CREATE DATABASE swiss")
dbSendQuery(con, "USE swiss")
```

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

### Create and Use Alternative Database in ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Demonstrates creating a new database and switching to it within the ClickHouse session. The `dbname` argument in `dbConnect` can also be used to specify the database upon connection.

```R
dbSendQuery(con, "CREATE DATABASE swiss")
dbSendQuery(con, "USE swiss")

```

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

### Create ClickHouseHTTP DBI Driver

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Initializes a ClickHouseHTTP DBI driver, which is the entry point for establishing connections to ClickHouse.

```APIDOC
## ClickHouseHTTP()

### Description
Create a ClickHouseHTTP DBI driver

### Usage
```
ClickHouseHTTP()

```

### Value
A ClickHouseHTTPDriver
```

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

### Access table from a different database

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Illustrates how to access a table located in a different database (e.g., 'default') from the currently active one. This is done by fully qualifying the table name using `SQL()`.

```R
dbReadTable(con, SQL("default.mtcars"))
```

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

### Establish HTTP Connection to ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Connect to a ClickHouse instance using HTTP. Ensure the ClickHouseHTTP package and DBI are loaded.

```R
library(DBI)
### HTTP connection ----

con <- dbConnect(
  ClickHouseHTTP::ClickHouseHTTP(),
  host = "localhost",
  port = 8123
)

```

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

### Create ClickHouseHTTP DBI Driver

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Instantiates a ClickHouseHTTP driver object for use with DBI functions.

```R
ClickHouseHTTP()
```

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

### Connect to ClickHouse via HTTPS (without SSL verification)

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Establishes a connection to a ClickHouse database using the HTTPS protocol. Use `ssl_verifypeer = FALSE` for connections where SSL certificate verification is not required or feasible.

```R
con <- dbConnect(
  ClickHouseHTTP::ClickHouseHTTP(),
  host = "localhost",
  port = 8443,
  https = TRUE,
  ssl_verifypeer = FALSE
)
```

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

### Connect to ClickHouse via HTTP

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Establishes a connection to a ClickHouse database using the HTTP protocol. Ensure the ClickHouse server is accessible on the specified host and port.

```R
library(DBI)
con <- dbConnect(
  ClickHouseHTTP::ClickHouseHTTP(),
  host = "localhost",
  port = 8123
)
```

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

### ClickHouseHTTPConnection Methods

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Provides methods for interacting with a ClickHouse database connection, including sending queries, retrieving information, and managing tables.

```APIDOC
## dbSendQuery

### Description
Send SQL query to ClickHouse

### Usage
```R
dbSendQuery(conn, statement, format = c("Arrow", "TabSeparatedWithNamesAndTypes"), file = NA, ...)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`statement`: the SQL query statement
`format`: the format used by ClickHouse to send the results. Two formats are supported: "Arrow" (default) and "TabSeparatedWithNamesAndTypes"
`file`: a path to a file to send along the query (default: NA)
`...`: Other parameters passed on to methods
```

```APIDOC
## dbGetInfo

### Description
Information about the ClickHouse database

### Usage
```R
dbGetInfo(dbObj, ...)
```

### Arguments
`dbObj`: a ClickHouseHTTPConnection object
`...`: Other parameters passed on to methods
```

```APIDOC
## dbListTables

### Description
List tables in ClickHouse

### Usage
```R
dbListTables(conn, database = NA, ...)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`...`: Other parameters passed on to methods
```

```APIDOC
## dbExistsTable

### Description
Does a table exist?

### Usage
```R
dbExistsTable(conn, name, database = NA, ...)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`...`: Other parameters passed on to methods
```

```APIDOC
## dbReadTable

### Description
Read database tables as data frames

### Usage
```R
dbReadTable(conn, name, database = NA, ...)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`...`: Other parameters passed on to methods
```

```APIDOC
## dbListFields

### Description
List field names of a table

### Usage
```R
dbListFields(conn, name, database = NA, ...)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`...`: Other parameters passed on to methods
```

```APIDOC
## dbRemoveTable

### Description
Remove a table from the database

### Usage
```R
dbRemoveTable(conn, name, database = NA, ...)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`...`: Other parameters passed on to methods
```

```APIDOC
## dbCreateTable

### Description
Create a table in ClickHouse

### Usage
```R
dbCreateTable(conn, name, database = NA, fields, engine = "TinyLog", overwrite = FALSE, ..., row.names = NULL, temporary = FALSE)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table to create
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`fields`: a character vector with the name of the fields and their ClickHouse type (e.g. `c("text_col String", "num_col Nullable(Float64)", "nul_col Array(Int32)")` )
`engine`: the ClickHouse table engine as described in ClickHouse documentation. Examples:
  * "TinyLog" (default)
  * "MergeTree() ORDER BY (expr)" (expr generally correspond to fields separated by ",") 
`overwrite`: if TRUE and if a table with the same name exists, then it is deleted before creating the new one (default: FALSE)
`...`: Other parameters passed on to methods
`row.names`: unsupported parameter (add for compatibility reason)
`temporary`: unsupported parameter (add for compatibility reason)
```

```APIDOC
## dbAppendTable

### Description
Insert rows into a table

### Usage
```R
dbAppendTable(conn, name, database = NA, value, ..., row.names = NULL)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`value`: a data.frame
`...`: Other parameters passed on to methods
`row.names`: unsupported parameter (add for compatibility reason)
```

```APIDOC
## dbWriteTable

### Description
Write a table in ClickHouse

### Usage
```R
dbWriteTable(conn, name, database = NA, value, overwrite = FALSE, append = FALSE, engine = "TinyLog", ..., row.names = NULL)
```

### Arguments
`conn`: a ClickHouseHTTPConnection object created with `dbConnect()`
`name`: the name of the table
`database`: the database to consider. If NA (default), the default database or the one in use in the session (if a session is defined).
`value`: a data.frame
`overwrite`: if TRUE and if a table with the same name exists, then it is deleted before creating the new one (default: FALSE)
`append`: if TRUE, the values are added to the database table if it exists (default: FALSE).
`engine`: the ClickHouse table engine as described in ClickHouse documentation. Examples:
  * "TinyLog" (default)
  * "MergeTree() ORDER BY (expr)" (expr generally correspond to fields separated by ",") 
`...`: Other parameters passed on to methods
`row.names`: unsupported parameter (add for compatibility reason)
```

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

### List Tables in ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Retrieves a list of all tables within the specified or default database.

```R
dbListTables(conn, database = NA, ...)
```

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

### Query ClickHouse Table with Default Format

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Execute a SQL query on ClickHouse and retrieve results. By default, uses the Apache Arrow format.

```R
dbGetQuery(con, "SELECT car, mpg, cyl, hp FROM mtcars WHERE hp>=110")

```

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

### Create Table in ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Creates a new table in ClickHouse with specified fields and engine. Supports overwriting existing tables.

```R
dbCreateTable(
  conn,
  name,
  database = NA,
  fields,
  engine = "TinyLog",
  overwrite = FALSE,
  ...,
  row.names = NULL,
  temporary = FALSE
)
```

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

### Write and read table with special column names and list types

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Shows how to write an R data frame containing a list column (which maps to ClickHouse Array type) and column names with spaces to ClickHouse. It then reads the data back to verify.

```R
data("swiss")
swiss <- as_tibble(swiss, rownames = "province")
swiss <- mutate(swiss, "pr letters" = strsplit(province, ""))
dbWriteTable(
  con,
  "swiss",
  swiss,
  engine = "MergeTree() ORDER BY (Fertility, province)"
)
swissFromDB <- dbReadTable(con, "swiss")
```

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

### dbConnect for ClickHouseHTTP

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Establishes a connection to a ClickHouse database using the HTTP or HTTPS protocol. It supports various parameters for host, port, authentication, SSL verification, and session management.

```APIDOC
## Driver for the ClickHouse database using HTTP(S) interface
### Description
Driver for the ClickHouse database using HTTP(S) interface 
Connect to a ClickHouse database using the ClickHouseHTTP DBI 
### Usage
```R
## S4 method for signature 'ClickHouseHTTPDriver'
dbConnect(
  drv,
  host = "localhost",
  port = 8123L,
  dbname = "default",
  user = "default",
  password = "",
  https = FALSE,
  ssl_verifypeer = TRUE,
  host_path = NA,
  use_session = FALSE,
  session_timeout = 3600L,
  convert_uint = TRUE,
  extended_headers = list(),
  reset_handle = FALSE,
  settings = list(),
  ...
)
```

### Arguments
`drv` |  A driver object created by `ClickHouseHTTP()`  
---|---
`host` |  name of the database host (default: "localhost")  
`port` |  port on which the database is listening (default: 8123L)  
`dbname` |  name of the default database (default: "default")  
`user` |  user name (default: "default")  
`password` |  user password (default: "")  
`https` |  a logical to use the HTTPS protocol (default: FALSE)  
`ssl_verifypeer` |  a logical to verify SSL certificate when using HTTPS (default: TRUE)  
`host_path` |  a path to use on host (e.g. "ClickHouse/"): it allows to connect on a server behind a reverse proxy for example  
`use_session` |  a logical indicating if a session should be created and use in ClickHouse (default: FALSE)  
`session_timeout` |  timeout in seconds (default: 3600L seconds)  
`convert_uint` |  a logical: if TRUE (default), UInt ClickHouse data types are converted in the following R classes: 
  * UInt8 : logical 
  * UInt16: Date (when using Arrow format in dbSendQuery,ClickHouseHTTPConnection,character-method) 
  * UInt32: POSIXct (when using Arrow format in dbSendQuery,ClickHouseHTTPConnection,character-method)

  
`extended_headers` |  a named list with other HTTP headers (for example: `extended_headers=list("X-Authorization"="Bearer <token>")` can be used for OAuth access delegation)  
`reset_handle` |  a logical indicating how to manage Curl handles (see httr::handle_pool). If TRUE, handle reset is used (default: FALSE).  
`settings` |  list of Clickhouse settings  
`...` |  Other parameters passed on to methods  
### Value
A ClickHouseHTTPConnection 
### See Also
ClickHouseHTTPConnection
### Examples
```R
## Not run: 
## Connection ----

library(DBI)
### HTTP connection ----

con <- dbConnect(
  ClickHouseHTTP::ClickHouseHTTP(),
  host = "localhost",
  port = 8123
)

```
```

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

### Establish HTTPS Connection to ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Connect to a ClickHouse instance using HTTPS, with an option to disable SSL peer verification. Ensure the ClickHouseHTTP package and DBI are loaded.

```R
library(DBI)
### HTTPS connection (without ssl peer verification) ----

con <- dbConnect(
  ClickHouseHTTP::ClickHouseHTTP(),
  host = "localhost",
  port = 8443,
  https = TRUE,
  ssl_verifypeer = FALSE
)

```

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

### Execute ClickHouse query with TabSeparated format

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Executes a SQL query against ClickHouse and specifies the 'TabSeparatedWithNamesAndTypes' format for the result. This can be useful for specific data processing needs.

```R
selCars <- dbGetQuery(
  con,
  "SELECT car, mpg, cyl, hp FROM mtcars WHERE hp>=110",
  format = "TabSeparatedWithNamesAndTypes"
)
```

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

### Query ClickHouse Table with TabSeparated Format

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Execute a SQL query on ClickHouse and retrieve results using the TabSeparatedWithNamesAndTypes format. This can be faster than Arrow for wide tables but slower for long tables.

```R
selCars <- dbGetQuery(
  con,
  "SELECT car, mpg, cyl, hp FROM mtcars WHERE hp>=110",
  format = "TabSeparatedWithNamesAndTypes"
)
## Identifying the original ClickHouse data types
attr(selCars, "type")

```

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

### Read Table from a Different Database

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Access a table located in a different database (e.g., 'default') than the currently selected one. Uses SQL object for specifying the full table path.

```R
dbReadTable(con, SQL("default.mtcars"))

```

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

### Query ClickHouse using TabSeparatedWithNamesAndTypes format

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Retrieves data from ClickHouse using a specific format, `TabSeparatedWithNamesAndTypes`, which differs from the default Apache Arrow format. This can be useful for compatibility or specific parsing needs.

```R
selCars <- dbGetQuery(
  con,
  "SELECT car, mpg, cyl, hp FROM mtcars WHERE hp>=110",
  format = "TabSeparatedWithNamesAndTypes"
)
attr(selCars, "type")
```

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

### List Fields of a Table in ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Retrieves the names and types of fields for a specified table in ClickHouse.

```R
dbListFields(conn, name, database = NA, ...)
```

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

### Write Table with Custom Engine and Array Column

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Write an R data frame to ClickHouse, specifying a custom table engine and supporting R list columns which map to ClickHouse Array types. Note the support for spaces in column names.

```R
data("swiss")
swiss <- as_tibble(swiss, rownames = "province")
swiss <- mutate(swiss, "pr letters" = strsplit(province, ""))
dbWriteTable(
  con,
  "swiss",
  swiss,
  engine = "MergeTree() ORDER BY (Fertility, province)"
)

```

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

### Send SQL Query to ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Sends an SQL query to the ClickHouse database. Supports Arrow or TabSeparatedWithNamesAndTypes formats for results. Can optionally save results to a file.

```R
dbSendQuery(
  conn,
  statement,
  format = c("Arrow", "TabSeparatedWithNamesAndTypes"),
  file = NA,
  ...
)
```

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

### Read Table from ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Read an entire table from ClickHouse into an R data frame. Assumes a connection 'con' is established.

```R
carsFromDB <- dbReadTable(con, "mtcars")

```

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

### Write R data frame with complex types to ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Writes an R data frame to ClickHouse, including columns with R `list` types which are mapped to ClickHouse `Array` types. Supports spaces in column names and custom table engines.

```R
data("swiss")
swiss <- as_tibble(swiss, rownames = "province")
swiss <- mutate(swiss, "pr letters" = strsplit(province, ""))
dbWriteTable(
  con,
  "swiss",
  swiss,
  engine = "MergeTree() ORDER BY (Fertility, province)"
)
```

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

### Check if Table Exists in ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Verifies the existence of a specific table within the ClickHouse database.

```R
dbExistsTable(conn, name, database = NA, ...)
```

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

### Write a table to ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Writes an R data frame to a ClickHouse table. The `engine` argument can be used to specify table engine details like ordering.

```R
library(dplyr)
data("mtcars")
mtcars <- as_tibble(mtcars, rownames = "car")
dbWriteTable(con, "mtcars", mtcars)
```

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

### Read Table from ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Reads the entire content of a specified table from ClickHouse into a data frame.

```R
dbReadTable(conn, name, database = NA, ...)
```

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

### Character Recovery Function for ClickHouseHTTP

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Use this function to recover special characters in strings when using the TabSeparatedWithNamesAndTypes format. It handles newline, tab, carriage return, backspace, bell, form feed, single quote, and backslash characters.

```R
      .sp_ch_recov <- function(x){
         stringi::stri_replace_all_regex(
            x,
            c(
               "\n", "\t",  "\r", "\b",
               "\a", "\f", "\'",  "\\"
            ),
            c("\n", "\t", "\r", "\b", "\a", "\f", "'", "\\"),
            vectorize_all=FALSE
         )
      }

```

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

### Write R Data Frame to ClickHouse Table

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Write an R data frame to a ClickHouse table. Requires the dplyr package for data manipulation and assumes a connection 'con' is already established.

```R
library(dplyr)
data("mtcars")
mtcars <- as_tibble(mtcars, rownames = "car")
dbWriteTable(con, "mtcars", mtcars)

```

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

### Append Rows to ClickHouse Table

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Appends new rows of data to an existing table in ClickHouse.

```R
dbAppendTable(conn, name, database = NA, value, ..., row.names = NULL)
```

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

### Write Table to ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Writes a data frame to a ClickHouse table. Can overwrite or append data, and specifies the table engine.

```R
dbWriteTable(
  conn,
  name,
  database = NA,
  value,
  overwrite = FALSE,
  append = FALSE,
  engine = "TinyLog",
  ...
)
```

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

### Read a table from ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Reads data from a ClickHouse table into an R data frame. This is a basic read operation for a table previously written or existing in the database.

```R
carsFromDB <- dbReadTable(con, "mtcars")
```

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

### Identify ClickHouse data types

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Retrieves the ClickHouse data types associated with the columns of a query result. This is useful for understanding the underlying data structure.

```R
attr(selCars, "type")
```

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

### Remove Table from ClickHouse

Source: https://cran.r-project.org/web/packages/ClickHouseHTTP/refman/ClickHouseHTTP.html

Deletes a specified table from the ClickHouse database.

```R
dbRemoveTable(conn, name, database = NA, ...)
```

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