如何在 where 子句中使用别名？ [复制]

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，它是 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

如何在 where 子句中使用它？

我试过 zo 直接在 where 子句中使用那个 CASE 语句，但是失败了。

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)

Answer 1

SQL-Server docs 说：

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。

在MySQL doc 中类似，它说：

标准 SQL 不允许在 WHERE 子句中引用列别名。施加此限制是因为在评估 WHERE 子句时，可能尚未确定列值。

在MySQL中你至少可以reuse aliases in the SELECT clause

Answer 2

你不能，不能直接。

但是，如果您将整个查询包装在一个子查询中，它就可以正常工作。

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   

这意味着您不需要在WHERE 子句中重复CASE 语句。 （可维护和干燥）。

它也是一种结构，它允许优化器就好像你有只是在WHERE子句中重复了你自己。

它对于其他 RDBMS 也非常可移植。

在 SQL Server 中，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

您不能直接执行此操作...但您可以在其周围添加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

我可能遗漏了一些东西，但这肯定会涵盖它：

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