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Mysql中索引和约束的示例语句_Mysql_

2023-05-27 384人已围观

简介 Mysql中索引和约束的示例语句_Mysql_

外键

查询一个表的主键是哪些表的外键

 SELECT TABLE_NAME, COLUMN_NAME, CONSTRAINT_NAME, REFERENCED_TABLE_NAME, REFERENCED_COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE TABLE_SCHEMA = 'mydbname' AND REFERENCED_TABLE_NAME = '表名';

导出所有外键语句

 SELECT CONCAT('ALTER TABLE ', TABLE_NAME, ' ADD CONSTRAINT ', CONSTRAINT_NAME, ' FOREIGN KEY (', COLUMN_NAME, ') REFERENCES ', REFERENCED_TABLE_NAME, '(', REFERENCED_COLUMN_NAME, ') ON DELETE CASCADE ON UPDATE CASCADE;') FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE TABLE_SCHEMA = 'mydbname' AND REFERENCED_TABLE_NAME IS NOT NULL;

删除所有外键语句

 SELECT CONCAT('ALTER TABLE ', TABLE_NAME, ' DROP FOREIGN KEY ', CONSTRAINT_NAME, ';') FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE TABLE_SCHEMA = 'mydbname' AND REFERENCED_TABLE_NAME IS NOT NULL;

自增

导出创建自增字段的语句

 SELECT CONCAT( 'ALTER TABLE `', TABLE_NAME, '` ', 'MODIFY COLUMN `', COLUMN_NAME, '` ', UPPER( COLUMN_TYPE ), ' NOT NULL AUTO_INCREMENT COMMENT "',COLUMN_COMMENT,'";' ) as 'ADD_AUTO_INCREMENT' FROM information_schema.COLUMNS WHERE TABLE_SCHEMA = 'mydbname' AND EXTRA = UPPER( 'AUTO_INCREMENT' ) ORDER BY TABLE_NAME ASC;

创建删除所有自增字段

 SELECT CONCAT( 'ALTER TABLE `', TABLE_NAME, '` ', 'MODIFY COLUMN `', COLUMN_NAME, '` ', UPPER( COLUMN_TYPE ), ' NOT NULL;' ) as 'DELETE_AUTO_INCREMENT' FROM information_schema.COLUMNS WHERE TABLE_SCHEMA = 'mydbname' AND EXTRA = UPPER( 'AUTO_INCREMENT' ) ORDER BY TABLE_NAME ASC;

索引

导出所有索引

 SELECT CONCAT( 'ALTER TABLE `', TABLE_NAME, '` ', 'ADD ', IF ( NON_UNIQUE = 1, CASE UPPER( INDEX_TYPE ) WHEN 'FULLTEXT' THEN 'FULLTEXT INDEX' WHEN 'SPATIAL' THEN 'SPATIAL INDEX' ELSE CONCAT( 'INDEX `', INDEX_NAME, '` USING ', INDEX_TYPE ) END, IF ( UPPER( INDEX_NAME ) = 'PRIMARY', CONCAT( 'PRIMARY KEY USING ', INDEX_TYPE ), CONCAT( 'UNIQUE INDEX `', INDEX_NAME, '` USING ', INDEX_TYPE ))), CONCAT( '(`', COLUMN_NAME, '`)' ), ';' ) AS 'ADD_ALL_INDEX' FROM information_schema.STATISTICS WHERE TABLE_SCHEMA = 'mydbname' ORDER BY TABLE_NAME ASC, INDEX_NAME ASC;

删除所有索引

 SELECT CONCAT( 'ALTER TABLE `', TABLE_NAME, '` ', CONCAT( 'DROP ', IF ( UPPER( INDEX_NAME ) = 'PRIMARY', 'PRIMARY KEY', CONCAT( 'INDEX `', INDEX_NAME, '`' ))), ';' ) AS 'DELETE_ALL_INDEX' FROM information_schema.STATISTICS WHERE TABLE_SCHEMA = 'mydbname' ORDER BY TABLE_NAME ASC;

数据合并

在数据迁移合并的时候，比较棘手的是不同数据库主键重复，那么我们就要批量修改主键的值，为了避免重复我们可以把自增的数字改为字符串

步骤基本上有以下几步

取消主键自增
删除所有外键
修改主键字段为varchar
添加所有外键
修改主键的值
合并数据

修改主键值的时候要注意

如果包含id和pid这种自关联的情况下是不能直接修改值的，就需要先删除约束再添加。

比如

删除自约束

 ALTER TABLE `t_director` DROP FOREIGN KEY `fk_directorpid`;

修改值

 update t_director set directorid=directorid+100000000; update t_director set directorid=CONV(directorid,10,36); update t_director set directorpid=directorpid+100000000 WHERE directorpid is not null; update t_director set directorpid=CONV(directorpid,10,36) WHERE directorpid is not null;

添加自约束

 ALTER TABLE t_director ADD CONSTRAINT fk_directorpid FOREIGN KEY (directorpid) REFERENCES t_director(directorid) ON DELETE CASCADE ON UPDATE CASCADE;

注意

CONV(directorpid,10,36)后两个参数为原数字进制和要转换后的进制。
第一个参数只要内容是数字就算类型为varchar也可以转换。

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