通过Postgresql中的列将单行转换为多行

Question

我有一个 table cash_drawer 存储每天结束时每种货币面额的数量：

cash_drawer(
    date DATE,
    100 SMALLINT,
    50 SMALLINT,
    20 SMALLINT,
    10 SMALLINT,
    5 SMALLINT,
    1 SMALLINT
)

现在，在任何一天，我都希望将每个面额作为一行。

如果假设第 2016-11-25 天，如果我们有以下行：

+------------+-------+------+------+------+-----+-----+
| date       |  100  |  50  |  20  |  10  |  5  |  1  |
+------------+-------+------+------+------+-----+-----+
| 2016-11-25 |   5   |  12  |  27  |  43  | 147 | 129 |
+------------+-------+------+------+------+-----+-----+

现在我希望得到查询的输出：

+------------+--------+
|denomination|quantity|
+------------+--------+
|100         |5       |
+------------+--------+
|50          |12      |
+------------+--------+
|20          |27      |
+------------+--------+
|10          |43      |
+------------+--------+
|5           |147     |
+------------+--------+
|1           |129     |
+------------+--------+

有什么方法可以实现吗？如果您有任何其他建议，请随时提出。

Answer 1

使用json functions:

select key as denomination, value as quantity
from cash_drawer c,
lateral json_each(row_to_json(c))
where key <> 'date'
and date = '2016-11-25';

 denomination | quantity 
--------------+----------
 100          | 5
 50           | 12
 20           | 27
 10           | 43
 5            | 147
 1            | 129
(6 rows)

Test it here.

通过Postgresql中的列将单行转换为多行

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