我知道游标被人们所诟病,我尽量避免使用它们,但可能有一些合理的理由来使用它们。我有一个,我正在尝试使用一对游标:一个用于主表,另一个用于辅助表。主表游标遍历外循环中的主表。辅助表格光标遍历内部循环中的辅助表格。 问题是,主表游标显然正在进行并将主键列值[Fname]保存到本地变量@Fname中,但它没有获取辅助表中相应外键列的行。对于辅助表,它始终返回其外键列值与主表的第一行的主键列值相匹配的行。T-Sql光标不能继续提取
以下是我想要在真实存储过程中执行的一个非常简单的示例。 名是主表
SET NOCOUNT ON
DECLARE
@Fname varchar(50) -- to hold the fname column value from outer cursor loop
,@FK_Fname varchar(50) -- to hold the fname column value from inner cursor loop
,@score int
;
--prepare primary table to be iterated in the outer loop
DECLARE @Names AS Table (Fname varchar(50))
INSERT @Names
SELECT 'Jim' UNION
SELECT 'Bob' UNION
SELECT 'Sam' UNION
SELECT 'Jo'
--prepare secondary/detail table to be iterated in the inner loop
DECLARE @Scores AS Table (Fname varchar(50), Score int)
INSERT @Scores
SELECT 'Jo',1 UNION
SELECT 'Jo',5 UNION
SELECT 'Jim',4 UNION
SELECT 'Bob',10 UNION
SELECT 'Bob',15
--cursor to iterate on the primary table in the outer loop
DECLARE curNames CURSOR
FOR SELECT Fname FROM @Names
OPEN curNames
FETCH NEXT FROM curNames INTO @Fname
--cursor to iterate on the secondary table in the inner loop
DECLARE curScores CURSOR
FOR
SELECT FName,Score
FROM @Scores
WHERE Fname = @Fname
--*** NOTE: Using the primary table's column value @Fname from the outer loop
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT 'Outer loop @Fname = ' + @Fname
OPEN curScores
FETCH NEXT FROM curScores INTO @FK_Fname, @Score
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT ' FK_Fname=' + @FK_Fname + '. Score=' + STR(@Score)
FETCH NEXT FROM curScores INTO @FK_Fname, @Score
END
CLOSE curScores
FETCH NEXT FROM curNames INTO @Fname
END
DEALLOCATE curScores
CLOSE curNames
DEALLOCATE curNames
下面是我得到的结果。请注意,对于外部循环,它会显示最新的Fname,但是当Fname用作@Fname从辅助表中获取相关行以进行后续迭代时,它仍会获得与第一个匹配的行行(Bob)的主表。
Outer loop @Fname = Bob
FK_Fname=Bob. Score=10
FK_Fname=Bob. Score=15
Outer loop @Fname = Jim
FK_Fname=Bob. Score=10
FK_Fname=Bob. Score=15
Outer loop @Fname = Jo
FK_Fname=Bob. Score=10
FK_Fname=Bob. Score=15
Outer loop @Fname = Sam
FK_Fname=Bob. Score=10
FK_Fname=Bob. Score=15
请让我知道我做错了什么。 在此先感谢!
谢谢奥维迪乌。那就是诀窍! – Aamir 2008-10-28 19:46:25