Mysql中索引和約束的示例語句
發(fā)布日期：2022-02-21 12:10 | 文章來源：站長之家
外鍵
查詢一個(gè)表的主鍵是哪些表的外鍵
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';
導(dǎo)出所有外鍵語句
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;
刪除所有外鍵語句
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
導(dǎo)出創(chuàng)建自增字段的語句
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;
創(chuàng)建刪除所有自增字段
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
導(dǎo)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;
刪除所有索引
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;
數(shù)據(jù)合并
在數(shù)據(jù)遷移合并的時(shí)候，比較棘手的是不同數(shù)據(jù)庫主鍵重復(fù)，那么我們就要批量修改主鍵的值，為了避免重復(fù)我們可以把自增的數(shù)字改為字符串
步驟基本上有以下幾步
- 取消主鍵自增
- 刪除所有外鍵
- 修改主鍵字段為varchar
- 添加所有外鍵
- 修改主鍵的值
- 合并數(shù)據(jù)
修改主鍵值的時(shí)候要注意
如果包含id和pid這種自關(guān)聯(lián)的情況下是不能直接修改值的，就需要先刪除約束再添加。
比如
刪除自約束
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;
添加自約束
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)后兩個(gè)參數(shù)為原數(shù)字進(jìn)制和要轉(zhuǎn)換后的進(jìn)制。
第一個(gè)參數(shù)只要內(nèi)容是數(shù)字就算類型為varchar也可以轉(zhuǎn)換。
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