如何在 where 子句中使用别名？ [复制]

可能的重复：
在 WHERE 子句中引用列别名 https://stackoverflow.com/questions/8370114/referring-to-a-column-alias-in-a-where-clause

   SELECT
Trade.TradeId, 
Isnull(Securities.SecurityType,'Other') SecurityType, 
TableName,
CASE 
WHEN 
SecurityTrade.SecurityId IS NOT NULL  
THEN 
SecurityTrade.SecurityId
ELSE 
Trade.SecurityId
END AS PricingSecurityID,
sum(Trade.Quantity)OVER(Partition by Securities.SecurityType, SecurityTrade.SecurityId,Trade.Price, Buy,Long ) as sumQuantity,
--added porfolio id for Getsumofqantity
Trade.PortfolioId,

Trade.Price,
case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end Position
from
Fireball_Reporting..Trade

where porfolioid =5 and Position =1   

我想在我的 where 子句中使用 Position =1 这是 case 的别名

case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end Position

我如何在 where 子句中使用它？

我尝试直接在 where 子句中使用该 CASE 语句，但失败了。

WHERE Trade.SecurityId = @SecurityId AND PortfolioId = @GHPortfolioID AND
                (case when (Buy = 1 and Long = 1) then 1 when (Buy = 0 and Long = 0) then 1 else 0 end Position = 1)

The SQL Server 文档 http://msdn.microsoft.com/en-us/library/ms173451.aspx says:

column_alias 可以在 ORDER BY 子句中使用，但它不能在 WHERE、GROUP BY 或 HAVING 子句中使用.

类似的在MySQL 文档 http://dev.mysql.com/doc/refman/5.5/en/problems-with-alias.html它说：

标准SQL不允许在 WHERE 子句中引用列别名。施加此限制是因为当计算 WHERE 子句时，列值可能尚未确定。

In MySQL你至少可以重用别名SELECT clause https://stackoverflow.com/a/18020948/575376