SQL SERVER游标理解

DECLARE @TableName VARCHAR(50)
DECLARE @SQL NVARCHAR(1000)
DECLARE @lcErrMsg VARCHAR(200)

DECLARE cr_upd CURSOR FOR SELECT s2.name FROM syscolumns s JOIN sysobjects s2 ON s2.id = s.id
WHERE s.name = 'pdctno'
AND s2.[type] = 'U'
AND s2.name NOT IN ('mktxhglb','mkt_jmkc','mktbjzyb','mktfpglb','mktfpglbbak') --定义一个游标为cr_upd 内容为select........
OPEN cr_upd --打开游标
FETCH NEXT FROM cr_upd INTO @TableName--第一个没有数据滴，自动下移一行取值，【游标与while大区别在于，游标这里可以into很多列】
WHILE @@FETCH_STATUS = 0 --循环，当取值存在时
BEGIN--判定
PRINT @TableName
SELECT @SQL = 'update ' + @TableName + ' set pdctno = UPPER(pdctno) where pdctno COLLATE Chinese_PRC_CS_AS LIKE ''%[abcdefghijklmnopqrstuvwxyz]%'' '--查询一个修改语句
EXEC sp_executesql @SQL--执行这条修改语句
IF @@ERROR <> 0-
BEGIN
CLOSE cr_upd
DEALLOCATE cr_upd
ROLLBACK
SELECT @lcErrMsg = '更新表'+@TableName+'型号失败。'
RETURN --报错回滚
END
FETCH NEXT FROM cr_upd INTO @TableName--继续修改下一行数据
END--结束
CLOSE cr_upd--关闭游标
DEALLOCATE cr_upd--销毁游标