我在下面写的更新触发器的描述中得到null

Question

我有一个名为tr_log的日志表，其中描述列是反映更新详细信息的位置，但我在表中获得空记录。我已经完成了删除和插入操作，并插入了正确的语句

if ($http_x_forwarded_proto = "http") { return 301 https://$host$request_uri; }

Answer 1

与NULL连接的任何内容都会导致NULL。确保将所有变量/字段与COALESCE（）连接起来（如果你在SQL Server上，也可以使用ISNULL（））。

顺便说一句，触发器中的循环和游标对于性能来说非常糟糕。试试这个：

insert into tr_log(description)
    SELECT
        'Emp with ' + cast(dat2.id as nvarchar(20)) + dat2.[NameChanged] + dat2.[SalaryChanged]
    FROM (
        SELECT
            dat1.*,
            CASE
                WHEN oldname<>[newname] THEN ' with name ' + ISNULL([oldname],'NULL') + ' has been updated to ' + ISNULL([newname],'NULL')
                ELSE ''
            END AS [NameChanged],
            CASE
                WHEN oldsalary<>newsalary THEN ' with salary ' + cast(ISNULL(oldsalary,0) as nvarchar(20))+ ' has been updated to ' + cast(ISNULL(newsalary,0) as nvarchar(20))
                ELSE ''
            END AS [SalaryChanged]
        FROM (
            SELECT
                i.id AS [ID],i.name AS [newname],i.sal AS [newsalary],d.name AS [oldname],d.sal AS [oldsalary]
            FROM inserted i
            INNER JOIN deleted d On i.ID=d.ID
        ) dat1
    ) dat2