我如何在where子句中使用别名？ [重复]

Question

此问题已经在这里有了答案：

关闭7年前。

可能重复：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，这是大小写的别名

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

如何在where子句中使用它？

我尝试在where子句中直接使用该CASE语句，但失败了请帮助我

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)

Answer 1

column_alias可以在ORDER BY子句中使用，但

不能在WHERE，GROUP BY或HAVING子句中使用

。

与MySQL doc类似，它说：

标准SQL

不允许在WHERE子句中引用列别名

。之所以施加此限制，是因为在评估WHERE子句时，可能尚未确定列值。

但是在

MySQL

中，您可以使用一些trick to overcome this

Answer 2

SELECT
  *
FROM
(
  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
)
  AS data
WHERE
  Position = 1   

这意味着您不需要在CASE子句中重复WHERE语句。 （可维护和干燥）。

这也是允许优化器表现为

仿佛您
had只是在WHERE子句中重复自己的结构。
它对于其他RDBMS也是非常可移植的。
在SQL Server中，然后您还有另一个选择...
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,
  position.val AS Position
from
  Fireball_Reporting..Trade
CROSS APPLY
(
  SELECT
    case
      when (Buy = 1 and Long = 1) then 1
      when (Buy = 0 and Long = 0) then 1
                                  else 0
    end AS val
)
  AS position
where
  porfolioid = 5
  AND position.val = 1

Answer 3

Answer 4