Question

我试图在MS SQL Server的后续列中使用计算中一列的结果。

下面是我的SQL代码：

SELECT 
(SELECT 'EURUSD' AS a) AS symbol_name,
(SELECT TOP 1  ROUND(p.BidLast,5) FROM mt5_prices p WHERE p.Symbol LIKE 'EURUSD%') AS Bid,

(SELECT SUM(m.Volume) 
FROM mt5_positions m
WHERE m.Symbol LIKE 'EURUSD%' AND m.Login IN (SELECT u.Login FROM mt5_users u WHERE u."Group" LIKE 'real%') AND m."Action" = 0) AS TotalBuy,

(SELECT CASE 
WHEN 'EURUSD' LIKE 'USOIL%' OR 'EURUSD' LIKE 'UKOIL%' OR 'EURUSD' LIKE 'Bund%' THEN ROUND(TotalBuy/10*Bid,2) 
WHEN 'EURUSD' LIKE 'NGAS%' OR 'EURUSD' LIKE 'Copper%' THEN ROUND(TotalBuy/1*Bid,2)
ELSE ROUND(TotalBuy/100*Bid,2) END) AS ExpositionBuyLots

当然，返回的错误是：

SQL错误（207）：列名无效＆＃39; TotalBuy＆＃39;
列名称无效＆＃39;出价＆＃39;。

我的问题是：如何使用已经（或者说，＃34;即时＆＃34;）来自列的计算结果TotalBuy和Bid？我读到了有关计算列的信息，但不幸的是，无法修改数据库。

MS SQL Server 2012版。

编辑：以上功能在MySQL中可用，我希望在MS SQL中也可以实现。如果有人对解决方案感兴趣（我选择了@Damien，因为它最接近原始MySQL查询（是的，它是查询，从MySQL重写为MSSQL），即只需要小的SQL修改）：

SELECT * FROM    
(SELECT 'EURUSD' AS symbol_name) symbol_name

CROSS apply

(SELECT TOP 1  ROUND(p.AskLast,5) AS Ask FROM mt5_prices p WHERE p.Symbol LIKE 'EURUSD%') Ask

CROSS apply

(SELECT TOP 1  ROUND(p.BidLast,5) AS Bid FROM mt5_prices p WHERE p.Symbol LIKE 'EURUSD%') Bid

CROSS apply

(SELECT SUM(m.Volume) AS TotalBuy
FROM mt5_positions m
WHERE m.Symbol LIKE 'EURUSD%' AND m.Login IN (SELECT u.Login FROM mt5_users u WHERE u."Group" LIKE 'real%') AND m."Action" = 0) TotalBuy

CROSS apply

(SELECT SUM(m.Volume) AS TotalSell
FROM mt5_positions m
WHERE m.Symbol LIKE 'EURUSD%' AND m.Login IN (SELECT u.Login FROM mt5_users u WHERE u."Group" LIKE 'real%') AND m."Action" = 1) TotalSell

CROSS apply

(SELECT (CASE 
WHEN 'EURUSD' LIKE 'USOIL%' OR 'EURUSD' LIKE 'UKOIL%' OR 'EURUSD' LIKE 'Bund%' THEN ROUND(TotalBuy/10*Bid,2) 
WHEN 'EURUSD' LIKE 'NGAS%' OR 'EURUSD' LIKE 'Copper%' THEN ROUND(TotalBuy/1*Bid,2)
ELSE ROUND(TotalBuy/100*Bid,2) END) AS ExpositionBuyLots) ExpositionBuyLots

Answer 1

您可以使用其他子查询块来实现此目的：

SELECT (
        CASE 
            WHEN 'EURUSD' LIKE 'USOIL%'
                OR 'EURUSD' LIKE 'UKOIL%'
                OR 'EURUSD' LIKE 'Bund%'
                THEN ROUND(TotalBuy / 10 * Bid, 2)
            WHEN 'EURUSD' LIKE 'NGAS%'
                OR 'EURUSD' LIKE 'Copper%'
                THEN ROUND(TotalBuy / 1 * Bid, 2)
            ELSE ROUND(TotalBuy / 100 * Bid, 2)
            END
        ) AS ExpositionBuyLots, *
FROM (
    SELECT ( SELECT 'EURUSD' AS a ) AS symbol_name
          ,( SELECT TOP 1 ROUND(p.BidLast, 5)
            FROM mt5_prices p
            WHERE p.Symbol LIKE 'EURUSD%'
            ) AS Bid
          ,( SELECT SUM(m.Volume)
            FROM mt5_positions m
            WHERE m.Symbol LIKE 'EURUSD%'
                AND m.LOGIN IN (
                    SELECT u.LOGIN
                    FROM mt5_users u
                    WHERE u."Group" LIKE 'real%'
                    )
                AND m."Action" = 0
            ) AS TotalBuy
    ) AS R

Answer 2

您可以使用cross apply（或子查询）来引入其他select子句。计算每个select子句＆＃34;好像＆＃34;所有表达式都是并行计算的 - 这就是为什么单个select子句中的表达式之间不存在依赖关系的原因。

E.g：

select
    *
from
    sys.objects
        cross apply
    (select object_id + 10 as mega_object_id) u
        cross apply
    (select mega_object_id / 30 as little_object_id) w

Answer 3

您应该使用APPLY运算符。您可以使用YourTable

中APPLY的值

SELECT 
    ExpositionBuyLots = CASE 
        WHEN 'EURUSD' LIKE 'USOIL%' OR 'EURUSD' LIKE 'UKOIL%' OR 'EURUSD' LIKE 'Bund%' THEN ROUND(ComputedValues.TotalBuy/10*ComputedValues.Bid,2) 
        WHEN 'EURUSD' LIKE 'NGAS%' OR 'EURUSD' LIKE 'Copper%' THEN ROUND(ComputedValues.TotalBuy/1*ComputedValues.Bid,2)
        ELSE ROUND(ComputedValues.TotalBuy/100 * ComputedValues.Bid,2) END
FROM YourTable
OUTER APPLY (
    SELECT
        symbol_name = 'EURUSD',
        Bid         = (SELECT TOP 1  ROUND(p.BidLast,5) FROM mt5_prices p WHERE p.Symbol LIKE 'EURUSD%') ,
        TotalBuy    = (SELECT SUM(m.Volume) 
                          FROM mt5_positions m
                          WHERE m.Symbol LIKE 'EURUSD%' AND m.Login IN (SELECT u.Login FROM mt5_users u WHERE u."Group" LIKE 'real%') AND m."Action" = 0
                      ) 
) ComputedValues

MSSQL Server中不同列中计算中一列结果的使用

3 个答案: