MYSQL查询仅当引擎不是innodb时才更改Alter表引擎

Question

I would like to run one query that alter table's engine (ALTER TABLE table1 ENGINE = INNODB) only if the current engine is not INNODB.

How can I do that?

Update: I got a case of a query trying to alter the table's engine while its already innodb.

Answer 1

You can use

ALTER TABLE t ENGINE = InnoDB;

You can use this query. If db engine already InnoDB then nothing will happen. Output will be

MySQL returned an empty result set (i.e. zero rows)

if engine not in InnoDB, then it will convert to InnoDB.

Answer 2

The command has no effect if the table is already on InnoDB .

You can query the table engine from information_schema:

SELECT `ENGINE` from `information_schema`.`TABLES`
WHERE `TABLE_SCHEMA`='my_schema' AND `TABLE_NAME`='table1';

Answer 3

http://mysql.rjweb.org/doc.php/myisam2innodb#generating_alters provides several tips about converting from MyISAM to InnoDB, including:

To generate all the ALTERs to convert all the MyISAM tables to InnoDB:

SELECT  CONCAT('USE ', table_schema, ';  ALTER TABLE ', table_name, ' ENGINE=InnoDB;')
    FROM  information_schema.tables
    WHERE  engine = 'MyISAM'
      AND  table_schema NOT IN ('mysql', 'information_schema', 'performance_schema');

Then copy and paste the output into the mysql commandline tool.