將不同表中的兩個日期與條件進行比較

Question

點擊圖片查看表格結構和問題http://i.stack.imgur.com/odWKL.png

SELECT B.ENTITYID, 
       B.BALANCEDATE,
       B.BALANCE, 
       MIN(DATEDIFF(DAY,B.BALANCEDATE,C.STATUSDATE)) RECENT
FROM   BALANCES B JOIN STATUS C ON B.ENTITYID = C.ENTITYID
GROUP  BY B.ENTITYID, B.BALANCEDATE,B.BALANCE
HAVING B.ENTITYID =1

我已經嘗試了以下方法，但是不能做得更好，因為更多的嵌套選擇在訪問相似屬性時存在問題：

Answer 1

如果您正在使用SQL Server，請參閱@ ljh的答案 。 以下解決方案適用於MySQL。 由於MySQL不支持CTE和Window Function所以有點亂。

MySQL的

SET @entity_name = 'ABCD';

SELECT  b.*, d.Status
FROM    Entity a
        INNER JOIN Balances b
            ON a.EntityID = b.EntityID
        LEFT JOIN
        (
            SELECT  a.EntityID, 
                    a.StatusDate StartDate, 
                    b.StatusDate + Interval -1 DAY EndDate,
                    a.Status
            FROM
                    (
                        SELECT  b.*, @r1 := @r1 + 1 AS Row_number
                        FROM    `Entity` a
                                INNER JOIN Status b
                                    ON a.EntityID = b.EntityID
                                CROSS JOIN (SELECT @r1 := 0) rowCount
                        WHERE   a.EntityName = @entity_name
                        ORDER   BY b.Status ASC
                    ) a
                    LEFT JOIN
                    (
                        SELECT  b.*, @r2 := @r2 + 1 AS Row_number
                        FROM    `Entity` a
                                INNER JOIN Status b
                                    ON a.EntityID = b.EntityID
                                CROSS JOIN (SELECT @r2 := 1) rowCount
                        WHERE   a.EntityName = @entity_name
                        ORDER   BY b.Status ASC
                    ) b ON  a.Row_number = b.Row_number
        ) d 
        ON b.BalanceDate BETWEEN d.StartDate AND d.EndDate
WHERE   a.EntityName = @entity_name

• SQLFiddle演示

---

簡要分解

由於MySQL不支持窗口函數，例如ROW_NUMBER() ，因此下面的查詢使用User Variable為每條記錄提供類似於ROW_NUMBER()行號，然后用於在其他子查詢上加入。

SELECT  b.*, @r1 := @r1 + 1 AS Row_number
FROM    `Entity` a
        INNER JOIN Status b
            ON a.EntityID = b.EntityID
        CROSS JOIN (SELECT @r1 := 0) rowCount
WHERE   a.EntityName = @entity_name
ORDER   BY b.Status ASC

• SQLFiddle演示

OUTPUT

╔══════════╦═════════════════════════════════╦════════╦════════════╗
║ ENTITYID ║           STATUSDATE            ║ STATUS ║ ROW_NUMBER ║
╠══════════╬═════════════════════════════════╬════════╬════════════╣
║        1 ║ May, 29 2010 00:00:00+0000      ║ A      ║          1 ║
║        1 ║ April, 16 2010 00:00:00+0000    ║ B      ║          2 ║
║        1 ║ April, 02 2010 00:00:00+0000    ║ C      ║          3 ║
║        1 ║ February, 26 2010 00:00:00+0000 ║ D      ║          4 ║
╚══════════╩═════════════════════════════════╩════════╩════════════╝

為記錄提供行號的主要目的是它將用於連接另一個子查詢，以便我們可以為每個Status獲取StartDate和EndDate 。 這在SQL Server 2012上很容易，因為它有一個名為LAG（）的窗口函數

╔══════════╦═════════════════════════════════╦══════════════════════════════╦════════╗
║ ENTITYID ║            STARTDATE            ║           ENDDATE            ║ STATUS ║
╠══════════╬═════════════════════════════════╬══════════════════════════════╬════════╣
║        1 ║ May, 29 2010 00:00:00+0000      ║ (null)                       ║ A      ║
║        1 ║ April, 16 2010 00:00:00+0000    ║ May, 28 2010 00:00:00+0000   ║ B      ║
║        1 ║ April, 02 2010 00:00:00+0000    ║ April, 15 2010 00:00:00+0000 ║ C      ║
║        1 ║ February, 26 2010 00:00:00+0000 ║ April, 01 2010 00:00:00+0000 ║ D      ║
╚══════════╩═════════════════════════════════╩══════════════════════════════╩════════╝

狀態范圍組織完成后。 現在，它已成為每個“ Balances的查閱狀態的基礎。

最終結果

╔══════════╦═════════════════════════════════╦═════════╦════════╗
║ ENTITYID ║           BALANCEDATE           ║ BALANCE ║ STATUS ║
╠══════════╬═════════════════════════════════╬═════════╬════════╣
║        1 ║ May, 01 2010 00:00:00+0000      ║     100 ║ B      ║
║        1 ║ April, 01 2010 00:00:00+0000    ║      50 ║ D      ║
║        1 ║ March, 01 2010 00:00:00+0000    ║      75 ║ D      ║
║        1 ║ February, 01 2010 00:00:00+0000 ║      85 ║ (null) ║
╚══════════╩═════════════════════════════════╩═════════╩════════╝

---

SQL Server 2012

MySQL演示的上述查詢可以通過使用Common Table Expression和使用LAG（）的Window Function在TSQL輕松轉換（ 僅在SQL Server 2012中引入 ）

WITH lookupTable
AS
(
    SELECT  EntityID, 
            StatusDate StartDate, 
            DATEADD(DAY, -1, LAG(StatusDate) OVER(PARTITION BY EntityID ORDER BY Status)) EndDate,
            Status
    FROM    Status
)
SELECT  b.*, d.Status
FROM    Entity a
        INNER JOIN Balances b
            ON a.EntityID = b.EntityID
        LEFT JOIN lookupTable d
            ON b.BalanceDate BETWEEN d.StartDate AND d.EndDate AND
               d.EntityID = a.EntityID
WHERE   a.EntityName = 'ABCD'

• SQLFiddle演示

OUTPUT

╔══════════╦═════════════════════════════════╦═════════╦════════╗
║ ENTITYID ║           BALANCEDATE           ║ BALANCE ║ STATUS ║
╠══════════╬═════════════════════════════════╬═════════╬════════╣
║        1 ║ May, 01 2010 00:00:00+0000      ║     100 ║ B      ║
║        1 ║ April, 01 2010 00:00:00+0000    ║      50 ║ D      ║
║        1 ║ March, 01 2010 00:00:00+0000    ║      75 ║ D      ║
║        1 ║ February, 01 2010 00:00:00+0000 ║      85 ║ (null) ║
╚══════════╩═════════════════════════════════╩═════════╩════════╝

Answer 2

以SQL Server 2012為RDBMS為例。 這是您需要的第一個查詢。
這個答案使用了SQL CTE（公用表表達式），它可能不適用於其他RDBMS系統。
SQL FIDDLE DEMO
查詢說明：
1.首先連接[Balances]和[Status]表，使用BalanceDate> StatusDate過濾出結果，從這兩個表中返回所有列，這是因為以后需要使用所有列。
2.使用[Entity]表加入Step .1的輸出，使用EntityName過濾掉結果，仍然保留3個表中的所有列，當然不需要重復EntityID。
3.使用CTE保存連接
4.使用CTE保存應用於聯接輸出的等級
5.使用等級編號按BalanceDate過濾結果和訂單

;with CTE_AfterJoin
as 
(
    select E.EntityID, E.EnityName, C.BalanceDate, C.Balance, C.StatusDate, C.status
    from Entity E
    left join (
            select B.EntityID, B.BalanceDate, B.Balance,S.StatusDate, S.[Status]
            from Balances B 
            left join  [Status] S
            on B.EntityID = S.EntityID and B.BalanceDate > S.StatusDate
            ) C
    on E.EntityID = C.EntityID
    where E.EnityName = 'ABCD'
),
CTE_afterRank
as 
(
    select EnityName, BalanceDate, Balance, 
           rank() over (partition by BalanceDate order by StatusDate desc) as Rn, Status 
    from CTE_AfterJoin
)
select EnityName, BalanceDate, Balance, Status
from CTE_afterRank
where Rn = 1
order by BalanceDate desc

Answer 3

同樣在SQLServer2005 +中，您可以使用APPLY（）運算符選項。

APPLY運算符允許您連接兩個表表達式。 每次對左表表達式中的每一行都處理右表表達式。最終結果集包含從左表表達式中選擇的所有列，然后是右表表達式的所有列。 對於右表表達式中沒有相應匹配項的行，OUTER APLLY在右表表達式的列中包含NULL值。

SELECT e.EntityName, b.BalanceDate AS Date, b.Balance, o.Status
FROM Entity e JOIN Balances b ON e.EntityID = b.EntityID
              OUTER APPLY (
                           SELECT TOP 1 s.Status AS Status                           
                           FROM Status s
                           WHERE b.EntityID = s.EntityID 
                             AND s.StatusDate < b.BalanceDate
                           ORDER BY s.StatusDate DESC
                           ) o
WHERE e.EntityName = 'ABCD' 

為了提高性能（強制INDEX SEEK操作），請將該索引與INCLUDE子句一起使用.INCLUDE子句將數據添加到最低/葉級別而不是索引樹中。 這使得索引更小，因為它不是樹的一部分

CREATE INDEX x ON Status(StatusDate) INCLUDE(EntityID, Status)
CREATE INDEX x ON Entity(EntityName) INCLUDE(EntityID)
CREATE INDEX x ON Balances(EntityID, BalanceDate, Balance)

在SQLFiddle上演示