Question

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？

我尝试在where子句中直接使用CASE语句但失败了请帮帮我

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

标准SQL 禁止在WHERE子句中引用列别名。强制执行此限制是因为在评估WHERE子句时，可能尚未确定列值。

Taken from MySQL Doc

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。

Taken from the MSSQL Doc

Answer 2

你不能，不能直接。

但是，如果将整个查询包装在子查询中，则可以正常工作。

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

这意味着您无需在CASE子句中重复WHERE语句。（可维护和干燥）。

它也是一种允许优化器表现的结构，好像只是在WHERE子句中重复。

它对其他RDBMS也非常便携。

在SQL Server中，您还有另一个选项......

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

你不能直接这样做......但是你可以在它周围包装一个额外的选择并使用where子句：

    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 and Position =1 
    )x
    where x.position = 1

Answer 4

我可能错过了一些东西但肯定会覆盖它：

WHERE (Buy = 1 and Long = 1) OR (Buy = 0 and Long = 0)

我如何在where子句中使用别名？

4 个答案: