以下是SQL语句和存储过程中的查询语句的流程控制的方法：

drop table classname
declare @TeacherID int
declare @a char(50)
declare @b char(50)
declare @c char(50)
declare @d char(50)
declare @e char(50)
set @TeacherID=1

select @a=DRClass1, @b=DRClass2, @c=DRClass3, @d=DRClass4, @e=DRClass5 from Teacher Where TeacherID = @TeacherID

create table classname(classname char(50))
insert into classname (classname) values (@a)
if (@b is not null)
begin
insert into classname (classname) values (@b)

if (@c is not null)
begin
insert into classname (classname) values (@c)

if (@d is not null)
begin
insert into classname (classname) values (@d)
if (@e is not null)
begin
insert into classname (classname) values (@e)
end
end
end
end

select * from classname

　　以上这些SQL语句能不能转成一个存储过程？自己试了下

ALTER PROCEDURE Pr_GetClass

@TeacherID int,
@a char(50),
@b char(50),
@c char(50),
@d char(50),
@e char(50)
as

select @a=DRClass1, @b=DRClass2, @c=DRClass3, @d=DRClass4, @e=DRClass5 from Teacher Where TeacherID = @TeacherID
DROP TABLE classname
create table classname(classname char(50))

insert into classname (classname) values (@a)
if (@b is not null)
begin
insert into classname (classname) values (@b)

if (@c is not null)
begin
insert into classname (classname) values (@c)

if (@d is not null)
begin
insert into classname (classname) values (@d)
if (@e is not null)
begin
insert into classname (classname) values (@e)
end
end
end
end

select * from classname

　　但是这样的话，这个存储过程就有6个变量，实际上应该只提供一个变量就可以了。

　　主要的问题就是自己没搞清楚 @a,@b,@C,@d 等是临时变量，是放在as后面重新做一些申明的，而不是放在开头整个存储过程的变量定义。

　　写好的存储过程如下:

create PROCEDURE Pr_GetClass
@TeacherID int
as

Declare @a char(50), @b char(50), @c char(50), @d char(50), @e char(50)
select @a=DRClass1, @b=DRClass2, @c=DRClass3, @d=DRClass4, @e=DRClass5 from Teacher Where TeacherID = @TeacherID
DROP TABLE classname
create table classname(classname char(50))
insert into classname (classname) values (@a)
if (@b is not null)
begin
insert into classname (classname) values (@b)
if (@c is not null)
begin
insert into classname (classname) values (@c)
if (@d is not null)
begin
insert into classname (classname) values (@d)
if (@e is not null)
begin
insert into classname (classname) values (@e)
end
end
end
end
select * from classname
go

　　2 连表查询

我有三个表
KJ表
KJID
TeacherID
..........................................................

Teacher表

TeacherID
TeacherName
CollageID
.........................................................

Collage表

CollageID
CollageName

　　我想写一个SQL语句，查询所有的KJ，根据KJ的TeacherID查到TeacherName,同时根据TeacherID查到Teacher，Teacher的CollageID查到Collage，最后生成的数据集里KJ的属性里除了本身的KJName以外，还想加上TeacherName，CollageName。

　　语句如下:

SELECT T1.KJName, T2.TeacherName, T3.CollageName
FROM KJ T1
LEFT JOIN Teacher T2 ON T2.TeacherID=T1.TeacherID
LEFT JOIN Collage T3 ON T3.CollageID=T2.CollageID