Question

如何转换以下内容：

+------+---------+------+
| Date | Product | Sold |
+------+---------+------+
| 1/1  | P1      |  100 |
| 1/1  | P2      |  250 |
| 1/1  | P3      |   50 |
| 2/1  | P1      |  170 |
| 2/1  | P2      |    0 |
| 2/1  | P3      |   70 |
+------+---------+------+

进入这样一个表：

+------+-----+-----+----+
| Date | P1  | P2  | P3 |
+------+-----+-----+----+
| 1/1  | 100 | 250 | 50 |
| 2/1  | 170 |   0 | 70 |
+------+-----+-----+----+

使用SQL？
我知道产品的数量（正好是3个）。

Answer 1

许多DBMS提供对“pivotots”或“交叉表报告”的特定支持，但如果您的DBMS没有，或者您更喜欢可以在各种DBMS上运行的解决方案，您可以写：

SELECT Date,
       MIN(CASE WHEN Product = 'P1' THEN Sold END) AS "P1",
       MIN(CASE WHEN Product = 'P2' THEN Sold END) AS "P2",
       MIN(CASE WHEN Product = 'P3' THEN Sold END) AS "P3"
  FROM ___insert_table_name_here___
 GROUP
    BY Date
;

编辑添加：您现在已经提到过您正在使用MySQL，不有特殊的数据透视或交叉表支持，所以上面的查询是要走的路。

Answer 2

如果是SQL Server 2005 +：

SELECT
    Date 
    , [P1]
    , [P2]
    , [P3]
FROM
(
    SELECT
        Date
        , Product
        , Sold
    FROM
        ProductSold
) AS t1
PIVOT
(
    MIN(Sold)
    FOR Product IN ([P1], [P2], [P3])
) AS pvt
ORDER BY
    Date ASC;

Answer 3

在MySQL中，如果要旋转的列数未知，则可以使用prepared statements，代码将如下所示（请参阅SQL Fiddle with Demo）：

CREATE TABLE Table1
    (`Date` datetime, `Product` varchar(7), `Sold` int)
;

INSERT INTO Table1
    (`Date`, `Product`, `Sold`)
VALUES
    ('2001-01-01 00:00:00', 'P1', 100),
    ('2001-01-01 00:00:00', 'P2', 250),
    ('2001-01-01 00:00:00', 'P3', 50),
    ('2001-02-01 00:00:00', 'P1', 170),
    ('2001-02-01 00:00:00', 'P2', 0),
    ('2001-02-01 00:00:00', 'P3', 70)
;

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'sum(case when Product = ''',
      Product,
      '''  then sold else 0 end) AS ',
      Product
    )
  ) INTO @sql
FROM Table1;

SET @sql = CONCAT('SELECT Date, ', @sql, ' 
                  FROM table1 
                  GROUP BY date');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SQL使用行作为列

3 个答案: