4.3 文本协议

4.3.1 Supported

• COM_INIT_DB
  Specifies the default schema for the connection.
• COM_PING
  Sends a packet containing one byte to check that the connection is active.
• COM_QUERY
  Sends the server an SQL statement to be executed immediately.Support Multi-Statement.
• COM_QUIT
  Client tells the server that the connection should be terminated.
• COM_SET_OPTION
  Enables or disables server option.
• COM_CHANGE_USER
  Resets the connection and re-authenticates with the given credentials.
• COM_RESET_CONNECTION
  Resets a connection without re-authentication.
  • 关闭后端连接(rollback & unlock)
  • 事务状态情况
  • 用户变量清空
  • 系统变量恢复成系统默认值
  • prepare清空
  • 上下文(字符集，隔离级别)恢复成为默认值
  • LAST_INSERT_ID 置零
• COM_FIELD_LIST
  MySQL Doc said that it is deprecated from 5.7.11 . But some tools are still use it, like OGG or MariaDB client.

4.3.1.1 Multi-Statement

• Supported
  • DML:select/insert/update/replace/delete
  • DDL
  • OTHER
    • BEGIN;
    • COMMIT;
    • LOCK TABLE
    • UNLOCK TABLES
    • START
    • KILL
    • USE
    • ROLLBACK
    • MYSQL_CMD_COMMENT
    • MYSQL_COMMENT
    • SELECT VERSION_COMMENT ( SELECT @@VERSION_COMMENT)
    • SELECT DATABASE（ select database() ）
    • SELECT USER（select user()）
    • SELECT VERSION (select version())
    • SELECT SESSION_INCREMENT(select @@session.auto_increment_increment)
    • SELECT SESSION_ISOLATION(select @@session.tx_isolation)
    • SELECT LAST_INSERT_ID(select last_insert_id(#) as id)
    • SELECT IDENTITY(select @@identity)
    • SELECT SESSION_TX_READ_ONLY（select @@session.tx_read_only）
• Not Supported
  • EXPLAIN
  • EXPLAIN2
  • DESCRIBE
  • SET
  • SHOW DATABASES/TABLES/TABLE_STATUS/COLUMNS/INDEX/CREATE_TABLE/VARIABLES/CREATE_VIEW/CHARSET
  • HELP
  • LOAD_DATA_INFILE_SQL
  • CREATE_VIEW
  • REPLACE_VIEW
  • ALTER_VIEW
  • DROP_VIEW

4.3.2 Not Supported

• COM_DEBUG
  Forces the server to dump debug information to stdout
• COM_STATISTICS
  Get internal server statistics.
• COM_CREATE_DB
• COM_DROP_DB

4.3.3 Internal

• COM_SLEEP
  Used inside the server only.
• COM_CONNECT an internal command in the server.
• COM_TIME an internal command in the server.
• COM_DAEMON an internal command in the server.
• COM_DELAYED_INSERT an internal command in the server.

4.3.4 Deprecated

• COM_PROCESS_INFO
  Deprecated from 5.7.11.
• COM_PROCESS_KILL
  Deprecated from 5.7.11.
• COM_SHUTDOWN
  Deprecated from 5.7.9.
• COM_REFRESH
  Deprecated from 5.7.11.