Question

我正在尝试记录过渡表和日期表。

表A：

date
2017-01-01
2017-01-02
2017-01-03
2017-01-04

表B：

state | date_logged | requestno_i
  A      2017-01-01      req01
  B      2017-01-03      req01
  C      2017-01-04      req01

预期结果：

   date      | state | date_logged | requestno_i
2017-01-01       A      2017-01-01      req01
2017-01-02       A      2017-01-01      req01
2017-01-03       B      2017-01-03      req01
2017-01-04       C      2017-01-04      req01

这是我的尝试：

SELECT 
A.date,
B.state,
B.date_logged,
B.requestno_i
FROM   TABLE_A A CROSS JOIN TABLE_B B
WHERE requestno_i='req01' and A.date>=B.date_logged

Answer 1

执行此操作的一种方法是使用CROSS APPLY而不是CROSS JOIN。例如：

DECLARE @TableA TABLE ([Date] DATE);
INSERT @TableA ([Date]) VALUES ('2017-01-01'), ('2017-01-02'), ('2017-01-03'), ('2017-01-04');

DECLARE @TableB TABLE ([State] CHAR(1), Date_Logged DATE, RequestNo_i VARCHAR(10));
INSERT @TableB ([State], Date_Logged, RequestNo_i) VALUES ('A', '2017-01-01', 'req01'), ('B', '2017-01-03', 'req01'), ('C', '2017-01-04', 'req01');

SELECT A.[Date], B.[State], B.Date_Logged, B.RequestNo_i
FROM @TableA AS A
CROSS APPLY
(
    SELECT TOP 1 *
    FROM @TableB
    WHERE Date_Logged <= A.[Date]
    AND RequestNo_i = 'req01'
    ORDER BY Date_Logged DESC
) AS B;

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1 个答案: