外鍵
查詢一個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
導出創建自增字段的語句
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;
數據合并
在數據遷移合并的時候，比較棘手的是不同數據庫主鍵重復，那么我們就要批量修改主鍵的值，為了避免重復我們可以把自增的數字改為字符串
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
- 合并數據
修改主鍵值的時候要注意
如果包含id和pid這種自關聯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)后兩個參數為原數字進制和要轉換后的進制。
第一個參數只要內容是數字就算類型為varchar也可以轉換。
以上就是Mysql中索引和約束的示例語句的詳細內容，更多關于MySQL 索引和約束的資料請關注腳本之家其它相關文章！
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