COM_CHANGE_USER resets the connection and re-authenticates with the given credentials. The packet is identical to the authentication packet in the connection handshake.

Fields

• int<1> 0x11 : COM_CHANGE_USER header

• string username

• if (server_capabilities & CLIENT_SECURE_CONNECTION)

  • int<1> length of authentication response

  • string authentication response

• else

  • string authentication response

• string default schema name

• int<2> client character collation

• if (server_capabilities & CLIENT_PLUGIN_AUTH)

  • string authentication plugin name

• if (server_capabilities & CLIENT_CONNECT_ATTRS)

  • int size of connection attributes

  • loop:

    • string key

    • string value

Response

Server response is like connection authentication :

• An OK packet in case of success OK_Packet.

• An error packet in case of error ERR_Packet.

• Authentication switch

  • If the client or server doesn't have PLUGIN_AUTH capability:

    • Server sends 0xFE byte .

    • Client sends old_password.

  • else

    • Server sends Authentication switch request.

    • Client may have many exchanges with the server according to the Plugin.

  • Authentication switch ends with server sending either OK_Packet or ERR_Packet.

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Warning: This command is deprecated and not used by MariaDB connectors any more. Please use the SQL statements CREATE SCHEMA or CREATE DATABASE instead.

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The COM_DEBUG command forces the server to dump debug information to stdout. It requires super privileges.

Fields

• int<1> 0xOD : COM_DEBUG Header

Response

EOF Packet

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Warning: This command is deprecated and not used by MariaDB connectors any more. Please use the SQL statements DROP SCHEMA or DROP DATABASE instead.

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Warning: This command is deprecated and not used by MariaDB connectors any more. Please use the SQL statements SHOW COLUMNS or SELECT FROM INFORMATION_SCHEMA.COLUMNS instead.

Fields

• int<1> 0x04 : COM_FIELD_LIST Header

Response

• n resultset row

• EOF_Packet

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COM_INIT_DB is used to specify the default schema for the connection.

Fields

• int<1> 0x02 : COM_INIT_DB Header

• string schema name

Response

ERR_Packet or OK_Packet

Example

06 00 00 00 02 74 65 73 74 63                    .....testc

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COM_PING permits sending a packet containing one byte to check that the connection is active.

Fields

• int<1> 0x0e : COM_PING Header

Response

OK_Packet

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Forces the server to terminate a specified connection.

Fields

• int<1> 0xC COM_PROCESS_KILL

• int<4> process id

Response

OK Packet or ERR Packet

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Warning: This command is deprecated and not used by MariaDB connectors any more. Please use the SQL statement SHOW PROCESSLIST instead.

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With the COM_QUERY command, the client sends the server an SQL statement to be executed immediately.

Fields

• int<1> 0x03 : COM_QUERY header

• string SQL statement

The SQL statement should be properly escaped. The escape character is usually a backslash '' = 0x5c. However, if the status flag returned by the last OK Packet had NO_BACKSLASH_ESCAPES bit set then the escape character is a single quote(' = 0x60)

If the escape character is a backslash, the following characters are escaped:

• single quote (' = 0x60)

• back slash (\ = 0x5c)

• double quote (" = 0x22)

• null character (0x00)

If the escape character is a single quote, only the single quote (' = 0x60) can be escaped.

Response

The server can answer with 4 different responses that can be differentiated by the first byte (packet header):

• 0xFF - ERR_Packet if any error occurs.

• 0x00 - OK_Packet when query execution works without resultset.

• 0xFB - LOCAL_INFILE Packet if the query was "LOCAL INFILE ...".

• Or a Resultset, when the query returns results (in case of a SELECT query for example).

Example

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Using the COM_QUIT command, the client tells the server that the connection should be terminated.

Fields

• int<1> 0x01 : COM_QUIT Header

Response

Server terminates connection.

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COM_RESET_CONNECTION Resets a connection without re-authentication.

This will :

• rollback any open transaction

• reset transaction isolation level

• reset session variables

• delete user variables

• remove temporary tables

• remove all PREPARE statement

Database will NOT be reset to initial value.

Fields

• int<1> 0x1f : COM_RESET_CONNECTION Header

Response

ERR_Packet or OK_Packet

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Enables or disables server option.

Fields

• int<1> 0x1B COM_SET_OPTION

• int<2> option

Options

Response

EOF Packet on success or ERR packet.

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Shuts down the server. To execute this command the SHUTDOWN privilege is required.

Fields

• int<1> 0x0A COM_SHUTDOWN

• int<1> option

Options

Response

OK Packet or ERR packet.

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This command is used inside the server only.

Direction

used inside server only

Fields

• int<1> 0x00 : COM_SLEEP header

Response

ERR_Packet

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Get internal server statistics.

Fields

• int<1> 0x09 : COM_STATISTICS Header

Response

string Human readable string

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