Question

这篇文章比其他帖子长得多，我为此道歉。所以，如果您对此感兴趣，请帮助我。

CREATE TABLE software_manual(
item_no varchar(50),
title varchar(50) NOT NULL,
description varchar(500),
manufacturer varchar(50),
version varchar(50),

CONSTRAINT software_manual_pk PRIMARY KEY(item_no),
CONSTRAINT check_sw_item_no CHECK (title LIKE '[S]%')
);

CREATE TABLE cpy_item(
access_no int,
status varchar(50),

CONSTRAINT cpy_item_pk PRIMARY KEY(access_no),
CONSTRAINT check_status CHECK(status IN ('Borrowed','Lost','Stolen','Available'))
);

CREATE TABLE cpy_software_manual(
access_no int,
item_no varchar(50),

CONSTRAINT cpy_software_manual_pk PRIMARY KEY(access_no),
CONSTRAINT cpy_software_manual_fk FOREIGN KEY(item_no) REFERENCES software_manual(item_no),
CONSTRAINT cpy_software_manual_fk2 FOREIGN KEY(access_no) REFERENCES cpy_item(access_no)
);

我为上面的表创建一个视图，如下所示

CREATE VIEW vw_sw_manual (title,manufacturer,version,access_no)
AS
SELECT sm.title,sm.manufacturer,sm.version,csm.access_no
FROM software_manual sm, cpy_software_manual csm
WHERE sm.item_no=csm.item_no;

我想写一个INSTEAD OF触发器到vw_sw_manual视图来做以下提到

我。如果插入的行包含表中存在的访问权限，则使用插入的数据更新software_manual表的版本，标题和制造商列。

II。否则，如果sofware_manual表中存在标题，制造商和版本，则在cpy_software_manual表中插入一个新行，其中的项目信息引用software_manual表的现有行

III。否则，将行插入software_manual和cpy_software_manual表以反映新信息。

我写了一个触发器，如下所示，它包含一些逻辑错误。在第二部分。我的问题@item_no在我的触发器中获取空值。任何人都可以帮我解决这个问题吗？

    alter TRIGGER tr_sw_vw_insert
    ON vw_sw_manual INSTEAD OF INSERT
    AS
    BEGIN
    DECLARE @insertAccessNo int
    DECLARE @title varchar(50)
    DECLARE @manufacturer varchar(5)
    DECLARE @version varchar(50)

    DECLARE @itemNo varchar(50)

    DECLARE @maxAccessNo int
    SELECT @maxAccessNo=MAX(access_no) FROM cpy_software_manual;

    SELECT @insertAccessNo=access_no,@title=title,@manufacturer=manufacturer,@version=version FROM inserted;

    IF(@insertAccessNo IS NOT NULL)
     BEGIN -- if @insertAccessNo IS NOT NULL do this
        SELECT @itemNo=item_no FROM cpy_software_manual WHERE access_no=@insertAccessNo;
        UPDATE software_manual SET title=@title,version=@version,manufacturer=@manufacturer
            WHERE item_no=@insertAccessNo;
     END
    ELSE IF(@title IS NOT NULL AND @manufacturer IS NOT NULL AND @version IS NOT NULL)
      BEGIN     

        INSERT INTO cpy_item(access_no,status) VALUES(@maxAccessNo+1,'Available');
        SELECT @itemNo=item_no FROM software_manual
          WHERE title=@title AND manufacturer=@manufacturer AND version=@version;

        INSERT INTO cpy_software_manual(access_no,item_no) VALUES(@maxAccessNo+1,@itemNo);

      END
    ELSE
      BEGIN-- else do this 
            DECLARE @maxItemNo int
            SELECT @maxItemNo=MAX(item_no) FROM software_manual;

            INSERT INTO software_manual(item_no,title,version,manufacturer)
                VALUES(@maxItemNo+1,@title,@version,@manufacturer);
            INSERT INTO cpy_item(access_no,status) VALUES(@maxAccessNo+1,'Available');
            INSERT INTO cpy_software_manual(access_no,item_no) VALUES(@maxAccessNo+1,@maxItemNo+1);
      END
END

Answer 1

alter TRIGGER tr_sw_vw_insert
ON vw_sw_manual INSTEAD OF INSERT
AS
BEGIN
DECLARE @insertAccessNo int
DECLARE @title varchar(50)
DECLARE @manufacturer varchar(5)
DECLARE @version varchar(50)

DECLARE @itemNo varchar(50)

DECLARE @maxAccessNo int
SELECT @maxAccessNo=MAX(access_no) FROM cpy_software_manual;

SELECT @insertAccessNo=access_no,@title=title,@manufacturer=manufacturer,@version=version FROM inserted;

IF(@insertAccessNo IS NOT NULL)
 BEGIN -- if @insertAccessNo IS NOT NULL do this
    SELECT @itemNo=item_no FROM cpy_software_manual WHERE access_no=@insertAccessNo;
    UPDATE software_manual SET title=@title,version=@version,manufacturer=@manufacturer
        WHERE item_no=@insertAccessNo;
 END
ELSE IF(@title IS NOT NULL AND @manufacturer IS NOT NULL AND @version IS NOT NULL)
  BEGIN     

    INSERT INTO cpy_item(access_no,status) VALUES(@maxAccessNo+1,'Available');
    SELECT @itemNo=item_no FROM software_manual
      WHERE title=@title AND manufacturer=@manufacturer AND version=@version;

    INSERT INTO cpy_software_manual(access_no,item_no) VALUES(@maxAccessNo+1,@itemNo);

  END
ELSE
  BEGIN-- else do this 
        DECLARE @maxItemNo int
        SELECT @maxItemNo=MAX(item_no) FROM software_manual;

        INSERT INTO software_manual(item_no,title,version,manufacturer)
            VALUES(@maxItemNo+1,@title,@version,@manufacturer);
        INSERT INTO cpy_item(access_no,status) VALUES(@maxAccessNo+1,'Available');
        INSERT INTO cpy_software_manual(access_no,item_no) VALUES(@maxAccessNo+1,@maxItemNo+1);
  END
END

在sql server中提前触发编程逻辑

1 个答案: