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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