sql - 如何向 "expand"当前有一个字段表示重复记录的表写入 sql 查询？

Question

我需要一个包含每个月记录的表，而不是具有重复计数字段的表。

我的数据目前如下所示:

Property       Item        Month          Repeat_Count      Amount
------------------------------------------------------------------
A              Rent        1/1/2016        1                100
A              Rent        2/1/2016        1                105
A              Rent        3/1/2016        3                110
A              Rent        6/1/2016        1                115
A              Rent        7/1/2016        6                120
A              Rent        1/1/2017        1                125

我希望它看起来像这样:

Property   Item      Month         Amount
-----------------------------------------
A          Rent      1/1/2016      100
A          Rent      2/1/2016      105
A          Rent      3/1/2016      110
A          Rent      4/1/2016      110
A          Rent      5/1/2016      110
A          Rent      6/1/2016      115
A          Rent      7/1/2016      120
A          Rent      8/1/2016      120
A          Rent      9/1/2016      120
A          Rent      10/1/2016     120
A          Rent      11/1/2016     120
A          Rent      12/1/2016     120
A          Rent      1/1/2017      125

希望我能很好地解释这一点，谢谢!

Answer 1

我会使用table of numbers和交叉应用。

数字表只是一个表，其中有一列包含从 1 到某个足够大的数字(例如 100,000)的整数。我个人使用包含 100K 数字的表格。 Aaron Bertrand 写了一个 good article解释如何生成这样的表。

示例数据

DECLARE @T TABLE ([Property] varchar(50), [Item] varchar(50), [Month] datetime, [Repeat_Count] int, [Amount] int);

INSERT INTO @T ([Property], [Item], [Month], [Repeat_Count], [Amount]) VALUES
('A', 'Rent', '2016-01-01 00:00:00', 1, 100),
('A', 'Rent', '2016-02-01 00:00:00', 1, 105),
('A', 'Rent', '2016-03-01 00:00:00', 3, 110),
('A', 'Rent', '2016-06-01 00:00:00', 1, 115),
('A', 'Rent', '2016-07-01 00:00:00', 6, 120),
('A', 'Rent', '2017-01-01 00:00:00', 1, 125);

查询

SELECT *
FROM
    @T AS T
    CROSS APPLY
    (
        SELECT
            DATEADD(day, dbo.Numbers.Number-1, T.Month) AS NewDate
        FROM dbo.Numbers
        WHERE dbo.Numbers.Number <= T.Repeat_Count
    ) AS CA
ORDER BY NewDate;

结果

+----------+------+-------------------------+--------------+--------+-------------------------+
| Property | Item |          Month          | Repeat_Count | Amount |         NewDate         |
+----------+------+-------------------------+--------------+--------+-------------------------+
| A        | Rent | 2016-01-01 00:00:00.000 |            1 |    100 | 2016-01-01 00:00:00.000 |
| A        | Rent | 2016-02-01 00:00:00.000 |            1 |    105 | 2016-02-01 00:00:00.000 |
| A        | Rent | 2016-03-01 00:00:00.000 |            3 |    110 | 2016-03-01 00:00:00.000 |
| A        | Rent | 2016-03-01 00:00:00.000 |            3 |    110 | 2016-03-02 00:00:00.000 |
| A        | Rent | 2016-03-01 00:00:00.000 |            3 |    110 | 2016-03-03 00:00:00.000 |
| A        | Rent | 2016-06-01 00:00:00.000 |            1 |    115 | 2016-06-01 00:00:00.000 |
| A        | Rent | 2016-07-01 00:00:00.000 |            6 |    120 | 2016-07-01 00:00:00.000 |
| A        | Rent | 2016-07-01 00:00:00.000 |            6 |    120 | 2016-07-02 00:00:00.000 |
| A        | Rent | 2016-07-01 00:00:00.000 |            6 |    120 | 2016-07-03 00:00:00.000 |
| A        | Rent | 2016-07-01 00:00:00.000 |            6 |    120 | 2016-07-04 00:00:00.000 |
| A        | Rent | 2016-07-01 00:00:00.000 |            6 |    120 | 2016-07-05 00:00:00.000 |
| A        | Rent | 2016-07-01 00:00:00.000 |            6 |    120 | 2016-07-06 00:00:00.000 |
| A        | Rent | 2017-01-01 00:00:00.000 |            1 |    125 | 2017-01-01 00:00:00.000 |
+----------+------+-------------------------+--------------+--------+-------------------------+