（刚学sql）sql语句中能加判断吗？比如IF什么的，可以的话格式是怎么样的？

[lunasea0]

如题

[zlp321002]

--类似这样
if exists(select 1 from tempdb..sysobjects where id=object_id('tempdb..#TMP1'))
drop table #TMP1
go
CREATE TABLE #TMP1 (CALLIDX BIGINT,AIIDX BIGINT)
select * from #TMP1

--或者
if @a>@b
begin
...
end
else
begin
....
end

[lunasea0]

需要连续判断是要用and连接吗？

[zhangyang555]

可以,例如:

if @a>@b and @c>@b or not(@d>@b or @c<>1)
begin
...
end
这里用到很多运算符,都能在sql中使用

[Alisa]

ELSE (IF...ELSE)（摘自联机丛书）
IF Boolean_expression { sql_statement | statement_block }
[
ELSE
{ sql_statement | statement_block } ]

当至少一本书满足这些条件时，这个示例会给出价格在 $10 与 $20 之间的传统烹调书的列表。否则，SQL Server 会给出一条信息，说明没有书满足这个条件，并生成价格低于 $10 的传统烹调书的列表。

USE pubs
GO
DECLARE @msg varchar(255)
IF (SELECT COUNT(price)
FROM titles
WHERE title_id LIKE 'TC%' AND price BETWEEN 10 AND 20) > 0

BEGIN
SET NOCOUNT ON
SET @msg = 'There are several books that are a good value between $10 and $20. These books are: '
PRINT @msg
SELECT title
FROM titles
WHERE title_id LIKE 'TC%' AND price BETWEEN 10 AND 20
END
ELSE
BEGIN
SET NOCOUNT ON
SET @msg = 'There are no books between $10 and $20. You might consider the following books that are under $10.'
PRINT @msg
SELECT title
FROM titles
WHERE title_id LIKE 'TC%' AND price < 10
END



还有一个IF...ELSE，你自己查一下