DROP MYSQL数据库中的所有外键

Question

外键导致我修改数据库结构以满足新要求时出现太多问题 - 我想修改主键但是当外键引用有问题的表时我似乎不能(我认为因为MySQL删除了表并重新创建) ).

因此,当我处理数据库时,我想简单地删除所有外键并在以后重新创建它们.这样做有一个简洁的方法吗？

Answer 1

跑

SELECT concat('ALTER TABLE ', TABLE_NAME, ' DROP FOREIGN KEY ', CONSTRAINT_NAME, ';') 
FROM information_schema.key_column_usage 
WHERE CONSTRAINT_SCHEMA = 'db_name' 
AND referenced_table_name IS NOT NULL;

并运行输出.

Answer 2

您可以在要创建的任何Alter Table语句之前发出以下命令:

SET foreign_key_checks = 0;

这将关闭数据库连接的外键约束检查.然后,您可以进行更改,而无需担心约束.

完成后,不要忘记发出:

SET foreign_key_checks = 1;

把它们重新打开.

请注意,这仍然不允许您创建因列数据类型不匹配而失败的新外键约束.

Answer 3

另一个版本的Zoozy代码,在这里您只能选择一个表:

SELECT concat('ALTER TABLE ', TABLE_NAME, ' DROP FOREIGN KEY ', CONSTRAINT_NAME, ';') 
FROM information_schema.key_column_usage 
WHERE CONSTRAINT_SCHEMA = 'YOUR DB HERE' 
AND TABLE_NAME='YOUR TABLE HERE' 
AND REFERENCED_TABLE_NAME IS NOT NULL;

还有一个程序:

DROP PROCEDURE IF EXISTS dropForeignKeysFromTable;

delimiter ///
create procedure dropForeignKeysFromTable(IN param_table_schema varchar(255), IN param_table_name varchar(255))
begin
    declare done int default FALSE;
    declare dropCommand varchar(255);
    declare dropCur cursor for 
        select concat('alter table ',table_schema,'.',table_name,' DROP FOREIGN KEY ',constraint_name, ';') 
        from information_schema.table_constraints
        where constraint_type='FOREIGN KEY' 
            and table_name = param_table_name
            and table_schema = param_table_schema;

    declare continue handler for not found set done = true;

    open dropCur;

    read_loop: loop
        fetch dropCur into dropCommand;
        if done then
            leave read_loop;
        end if;

        set @sdropCommand = dropCommand;

        prepare dropClientUpdateKeyStmt from @sdropCommand;

        execute dropClientUpdateKeyStmt;

        deallocate prepare dropClientUpdateKeyStmt;
    end loop;

    close dropCur;
end///