如何从单行创建多行 - 规范化表

2021-09-10 00:00:00 sql tsql sql-server-2008 sql-server

我对 SQL 很陌生，正在尝试解决这个问题:

I am pretty new to SQL and trying to figure this out:

我有一个名为 BUDGET 的表，其中包含一年中每个月的 12 列，显示该月的预算余额.所以表格看起来像这样:

I have a table called BUDGET that has 12 columns for each month of the year, displaying the budget balance of that month. So the table looks like this:

[Department]  [Year]  [Month1] [Month2] .... [Month12]  
ABCD           2010   $5000     $5500   .....  $4000
ABCD           2011   $6000     $6500   .....  $3000

我想要做的是标准化这个表并将每一行分成 12 行，每行有一个日期字段，格式如下.我还想有一个 [余额] 列来显示该月的值.因此，规范化的表将如下所示:

What I am trying to do is to normalize this table and break each row into 12 rows, each row with a date field in the following format. I also want to have a [Balance] column that displays the value of that month. So, the normalized table will look like this:

[Department]  [Date]     [Balance] 
ABCD          20100101     $5000   
ABCD          20100201     $5500 
ABCD          20100301     .....
ABCD          .......      ......

我尝试在同一张桌子上使用 CROSS JOIN 但失败了.我也尝试使用 while 循环，但也失败了.任何形式的帮助表示赞赏.谢谢！

I tried using CROSS JOIN on the same table but failed. I also tried using a while loop but that failed as well. Any kind of help is appreciated. Thanks!

我使用的是 SQL Server 2008

I am using SQL Server 2008

推荐答案

为了好玩，这里有一个 CROSS APPLY 解决方案:

Just for fun here's a CROSS APPLY solution:

SELECT
   B.Department,
   DateAdd(month, (B.Year - 1900) * 12 + M.Mo - 1, 0) [Date],
   M.Balance
FROM
   dbo.Budget B
   CROSS APPLY (
      VALUES
      (1, Month1), (2, Month2), (3, Month3), (4, Month4), (5, Month5), (6, Month6),
      (7, Month7), (8, Month8), (9, Month9), (10, Month10), (11, Month11), (12, Month12)
   ) M (Mo, Balance);

它与@Aaron Bertrand 的 UNPIVOT 没有什么不同，没有使用 UNPIVOT.

It's really no different than @Aaron Bertrand's UNPIVOT, without using UNPIVOT.

如果您必须将日期作为字符串，则将字符串放入 CROSS APPLY 中，如 ('01', Month1) 并将 SELECT 更改为 Convert(char(4),B.Year) + M.Mo.

If you must have the date as a string, then put strings in the CROSS APPLY like ('01', Month1) and change the SELECT to Convert(char(4), B.Year) + M.Mo.

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