如何从SQL Server数据库中删除所有外键？

Question

我要删除所有具有以下条件的外键。

SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE TABLE_NAME IN ('Table1', 'Table2')
  AND CONSTRAINT_NAME LIKE '%FK__%__DL%'

Answer 1

有一个名为的表INFORMATION_SCHEMA.TABLE_CONSTRAINTS，用于存储所有表约束。约束类型FOREIGN KEY也保留在该表中。因此，通过过滤此类型，您可以访问所有外键。

SELECT  *
FROM    INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE   CONSTRAINT_TYPE = 'FOREIGN KEY'

如果创建动态查询（用于-DROP对外键进行更改）以更改表，则可以达到更改所有表的约束的目的。

WHILE(EXISTS(SELECT 1 FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE = 'FOREIGN KEY' AND TABLE_NAME IN ('Table1', 'Table2') AND CONSTRAINT_NAME LIKE '%FK__%__DL%'))
BEGIN
    DECLARE @sql_alterTable_fk NVARCHAR(2000)

    SELECT  TOP 1 @sql_alterTable_fk = ('ALTER TABLE ' + TABLE_SCHEMA + '.[' + TABLE_NAME + '] DROP CONSTRAINT [' + CONSTRAINT_NAME + ']')
    FROM    INFORMATION_SCHEMA.TABLE_CONSTRAINTS
    WHERE   CONSTRAINT_TYPE = 'FOREIGN KEY'
            AND TABLE_NAME IN ('Table1', 'Table2')
            AND CONSTRAINT_NAME LIKE '%FK__%__DL%'

    EXEC (@sql_alterTable_fk)
END

EXISTS 函数及其参数可确保至少有一个外键约束。