从存储过程-sql-server根据布尔进行条件连接

Question

我有以下代码：

with cte1 as (

select ...... from TABLE 1......
where ......
)

with cte2 as 
( 
select .... from table2....
where.....
)

select cte1.id,cte2.name,cte2.last from cte1 join cte2 on cte1.id=cte2.id

我想要的是从存储过程中获取布尔变量。
确实如此时，我不想进行连接，也不想计算cte2。

就像是：

if(@BollVar=false)
select cte1.id,cte2.name,cte2.last from cte1 join cte2 on cte1.id=cte2.id
else
select cte1.id,cte1.cat from cte1 
(and here I don't want cte2 to be calculated, because I don't need it)

我该怎么办？

Answer 1

with cte1 as (

select ...... from TABLE 1......
where ......
)

with cte2 as 
( 
select .... from table2....
where.....
)

select cte1.id,cte2.name,cte2.last from cte1
left join
cte2 on cte1.id=cte2.id
And @BollVar = 0
Where
         @BollVar = 1
         Or cte2.id is not null

另一种方法是切换到左联接，如果变量为true，则不返回任何行，添加一个where语句以测试变量是否为true以返回所有内容，或者当cte2.id不为null时将其设为实际需要结果时进行内部联接。

之所以行之有效，是因为您可以放入几乎所有您想要的对联接条件评估为true或false的东西。

抱歉，格式化手机的首次尝试格式不正确