如何从具有复合主键的表中删除？答案

【问题标题】：How to delete from table with composite primary key?如何从具有复合主键的表中删除？
【发布时间】：2020-12-25 12:52:21
【问题描述】：

我有一个带有复合主键的表 Role。我必须从中删除值并检查它们是否不等于某个值（在触发器中）。我需要怎么做？

表格代码：

CREATE TABLE Role
(
    roleName VARCHAR(50),
    groupId  INT,
    CONSTRAINT FK_Group FOREIGN KEY (groupId) REFERENCES [Group] (groupId),
    PRIMARY KEY (roleName, groupId),
    canBan   TINYINT DEFAULT (0) /* 0 or 1 */
)

触发代码，未获批准


CREATE TRIGGER DeleteRoleTrigger
    ON [Role]
    INSTEAD OF DELETE
    AS
BEGIN
    IF 'everyone' IN (SELECT roleName FROM deleted)
        BEGIN
            THROW 50002, 'Cannot delete role "everyone"! Nothing is deleted', 1
            --   id severity state
        END
    ELSE
        BEGIN
            -- todo
            DELETE
            FROM Role
            WHERE (EXISTS(SELECT groupId, roleName FROM deleted))

            PRINT N'Роль удалена'
        END
END
GO

【问题讨论】：

exists 子查询与外部 (delete) 查询不相关。如果deleted 中存在任何行，那么它将删除Role 中的所有行。可能不是所需的功能。

标签： sql sql-server database tsql

【解决方案1】：

问题可能出在WHERE (EXISTS(SELECT groupId, roleName FROM deleted)) 行。我建议在delete语句中使用inner join，如下。

DELETE r
FROM Role r
INNER JOIN deleted d
  ON r.groupId = d.groupId AND r.roleName = d.roleName

【讨论】：

【解决方案2】：

您可能需要更改此触发器的 ELSE 部分

DELETE r
FROM [Role] r join deleted d
on (r.groupId = d.groupId and r.roleName =d.roleName)

或者

DELETE r
FROM [Role] r WHERE EXISTS(SELECT 1 FROM deleted d
WHERE d.groupId=r.groupId and d.roleName=r.roleName)

【讨论】：