游标的重复执行,该如何处理

游标的重复执行
表tableA:
----------------------------
  id name isFlag
  001 张三 0 
  002 李四 0 
  003 王五  
  004 赵六  
  005 陈七 1  
----------------------------
  我现在要取出tableA的isFlag，如果isFlag是1，执行一个update的操作；如果不为1，则执行另一个update的操作。
  下面是我用游标做的，为什么在else的里面，会重复执行多次？
-----------------------------
  DECLARE @isFlag char(1)  
  DECLARE CursorIsFlag CURSOR FOR
SELECT IsFlag FROM tableA FOR READ ONLY  
OPEN CursorIsFlag
FETCH NEXT FROM CursorIsFlag INTO @isFlag
WHILE @@FETCH_STATUS = 0  
BEGIN 
FETCH NEXT FROM CursorIsFlag INTO @isFlag  
IF @isFlag ='1'  
BEGIN  
UPDATE tableB
SET B.id='002'  
FROM tableA A LEFT JOIN tableB B  
ON A.id = B.id  
END  
ELSE  
UPDATE tabelC
SET B.id='003'  
FROM tableA A LEFT JOIN tabelC B  
ON A.id = B.id

FETCH NEXT FROM CursorIsFlag INTO @isFlag

END

CLOSE CursorIsFlag
DEALLOCATE CursorIsFlag
 
  Go
-----------------------------






[解决办法]
先改成这个样子再看逻辑：

SQL code

DECLARE @isFlag char(1)   DECLARE CursorIsFlag CURSOR FOR    SELECT IsFlag FROM tableA FOR READ ONLY   OPEN CursorIsFlag FETCH NEXT FROM CursorIsFlag INTO @isFlagWHILE @@FETCH_STATUS = 0   BEGIN           IF @isFlag ='1'       BEGIN           UPDATE tableB    SET B.id='002' FROM tableA A LEFT JOIN tableB B   ON A.id = B.id       END       ELSE       UPDATE tabelC    SET B.id='003' FROM tableA A LEFT JOIN tabelC B   ON A.id = B.id FETCH NEXT FROM CursorIsFlag INTO @isFlagENDCLOSE CursorIsFlagDEALLOCATE CursorIsFlag
[解决办法]
SQL code
    DECLARE @isFlag char(1)       DECLARE CursorIsFlag CURSOR FOR     SELECT IsFlag FROM tableA FOR READ ONLY       OPEN CursorIsFlag     FETCH NEXT FROM CursorIsFlag INTO @isFlag    WHILE @@FETCH_STATUS = 0       BEGIN            IF @isFlag ='1'           BEGIN               UPDATE b             SET B.id='002'               FROM tableA A LEFT JOIN tableB B               ON A.id = B.id           END           ELSE        begin               UPDATE b             SET B.id='003'               FROM tableA A LEFT JOIN tabelC B               ON A.id = B.id         end        FETCH NEXT FROM CursorIsFlag INTO @isFlag    END    CLOSE CursorIsFlag    DEALLOCATE CursorIsFlag        --你的游标里，每次更新的是所有能匹配上的数据，        --最终的结果是根据游标获取[color=#FF0000]最后的一条信息决定是 002 还是 003[/color]        --多次执行 是因为你的update语句原因