Question

我有64列，我正在尝试自动化循环过程。循环运行但它显示0个受影响的行。如果我逐列更新表，它可以工作。知道为什么它显示0个受影响的行以及可以做什么？

    update temp set col1 = 'C' where col1 IS Null; -- works (276 rows affected)--

    declare @count as int;
    declare @name as varchar(max);
    set @count = 2;
    while @count < (SELECT Count(*) FROM INFORMATION_SCHEMA.Columns where TABLE_NAME = 'temp')+1

    Begin
    Set @name = (select name from (select colorder, name from (SELECT * 
            FROM syscolumns WHERE id=OBJECT_ID('temp')) colnames) as cl where colorder = @count)
    Print @name
    update temp set @name = 'C' where @name IS Null;
    SET @count = @count + 1;
    END;

Answer 1

您需要在运行时使用动态SQL来更新不同的列，如下所示。

注意：我刚添加/修改了动态sql部分。

    declare @count as int;
    declare @name as varchar(max)
    declare @sql nvarchar (1000)
    set @count = 2
    while @count < (SELECT Count(*) FROM INFORMATION_SCHEMA.Columns where TABLE_NAME = 'temp')+1

    Begin
    Set @name = (select name from (select colorder, name from (SELECT * 
            FROM syscolumns WHERE id=OBJECT_ID('temp')) colnames) as cl where colorder = @count)
    Print @name

    set @sql = N'update temp set ' + @name + '= ''C'' where ' + @name + ' is null ';
    exec sp_executesql @sql
    SET @count = @count + 1
    END;

更新表的多列中的空值（SQL Server）

1 个答案: