Question

我可以删除带有这个SQL子句的记录，

DELETE FROM TABLE WHERE ID = 2

如果表计数= 1，即使“ID = 2”，我也需要留下一条记录。我怎么能这样做？

Answer 1

添加WHERE子句以确保有多行：

DELETE FROM TABLE 
WHERE ID = 2
AND (SELECT COUNT(*) FROM TABLE) > 1

Answer 2

未经测试，但有些内容可能会有效吗？

DELETE FROM TABLE WHERE ID = 2 LIMIT (SELECT COUNT(*)-1 FROM TABLE WHERE ID=2);

也许添加if语句以确保计数高于1.

Answer 3

简单的方法是禁止任何清空表格的删除

CREATE TRIGGER TRG_MyTable_D FOR DELETE
AS
IF NOT EXISTS (SELECT * FROM MyTable)
    ROLLBACK TRAN
GO

更复杂的是，如果你执行这个多行删除会清空表怎么办？

DELETE FROM TABLE WHERE ID BETWEEN 2 AND 5

所以，从你刚刚删除的内容中随机重新填充

CREATE TRIGGER TRG_MyTable_D FOR DELETE
AS
IF NOT EXISTS (SELECT * FROM MyTable)
    INSERT mytable (col2, col2, ..., coln)
    SELECT TOP 1 col2, col2, ..., coln FROM INSERTED --ORDER BY ??

GO

但是，要求有点危险和模糊。在英语中，好的，“表中至少有一行”，但实际上“哪一行？”

如果使用SQL，表记录计数= 1，我想总是保留一条记录

3 个答案: