为什么mysql中不允许在group by中使用别名?[复制品]

标准SQL 禁止在where子句中引用列别名 . 施加此限制是因为在计算where子句时,可能尚未确定列值。

Taken from MySQL Doc

CyrnNoLayas可以用在ORDY by子句中,但是 不能在where、group by或having子句中使用 .

Taken from the MSSQL Doc

你不能,不能直接。

但是,如果将整个查询包装在子查询中,则它可以正常工作。

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   

这意味着你不需要重复 CASE 语句在 WHERE 条款。(可维护且干燥)。

它也是一种结构,允许乐观者表现 犹如 你 有 只是重复你自己 哪里 条款。

它对其他RDBMS也是非常便携的。

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

你不能直接这样做,但是你可以在它周围包上一个附加的选择,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

我可能漏掉了一些东西,但这肯定能弥补:

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