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Overview of handler statement

Handler is similar to the select statement, but unlike the latter, it can only query records once at a time. Handler has some special features that are suitable for specific scenarios. This article introduces some knowledge about handler statements for later use.

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Official manual of handler sentences

Handler statement syntax

Example of handler statement

The handler statement applies to the scenario

Considerations for handler statement

Official manual of handler sentences 13 SQL Statement Syntax13.2 Data Manipulation Statements13.2.4 HANDLER Syntaxhandler sentence syntax

HANDLER tbl_name OPEN [[AS] alias] HANDLER tbl_name READ index_name {= | = |

} (value1,value2,...) [WHERE where_condition] [LIMIT...] HANDLER tbl_name READ index_name {FIRST | NEXT | PREV | LAST} [WHERE where_condition] [LIMIT...] HANDLER tbl_name READ {FIRST | NEXT} [WHERE where_condition] [LIMIT...] HANDLER tbl_name CLOSEhandler statement example

Specify an alias for handle to use multiple handle

HANDLER tbl_name OPEN [[AS] alias] mysql > handler t_table_lock open p1ten query OK, 0 rows affected (0.00 sec)

Open and close tables

HANDLER tbl_name OPEN [[AS] alias] HANDLER tbl_name CLOSEmysql > handler t_table_lock open;Query OK, 0 rows affected (0.00 sec) mysql > show open tables from zxydb like'Tablelocked' +-+ | Database | Table | In_use | Name_locked | +-+ | zxydb | t_table _ lock | 1 | 0 | +-+ 1 row in set (0.00 sec) mysql > handler t_table_lock close Query OK, 0 rows affected (0.00 sec) # # mysql > show open tables from zxydb like'Tablelocked' +-+ | Database | Table | In_use | Name_locked | +-+ | zxydb | t_table _ lock | 0 | 0 | +-+ 1 row in set (0.00 sec)

Read the record of the table

HANDLER tbl_name READ {FIRST | NEXT} [WHERE where_condition] [LIMIT.] # # get the first record of the table mysql > handler t_table_lock read first;+-+-+ | a | b | +-+-+ | 1 | 1 | +-+ 1 row in set (0.00 sec) # # get the next record of the table mysql > handler t_table_lock read next Empty set (0.00 sec)

Gets the table record of the specified index value

HANDLER tbl_name READ index_name {= | = |

} (value1,value2,...) [WHERE where_condition] [LIMIT...] mysql > handler t_table_lock read idx_a= (1); +-+-+ | a | b | +-+-+ | 1 | 1 | +-+-+ 1 row in set (0.00 sec) # # mysql > handler t_table_lock read idx_a= (2); Empty set (0.00 sec)

Gets the first, next, previous, and last table records of the specified index

HANDLER tbl_name READ index_name {FIRST | NEXT | PREV | LAST} [WHERE where_condition] [LIMIT...] # # mysql > handler t_table_lock read idx_a first;+-+-+ | a | b | +-+-+ | 1 | 1 | +-+-+ 1 row in set (0.00 sec) # # mysql > handler t_table_lock read idx_a next Empty set (0.00 sec) # # mysql > handler t_table_lock read idx_a last;+-+-+ | a | b | +-+-+ | 1 | 1 | +-+-+ 1 row in set (0.00 sec) # # mysql > handler t_table_lock read idx_a prev;Empty set (0.00 sec) handler statement applicable scenario

Considerations for handler statement

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