PHP 删除第二条记录组名称

Question

任何人都知道如何使用相同的组对记录进行分组，但下一行的组名称在 PHP/MySQL 中为空，例如:

数据库表上的记录:

| id | group_title | item     | qty | price
| 1  | G-01        | Mouse    |  1  |   $5
| 2  | G-01        | Keyboard |  1  |   $12
| 3  | G-01        | Keyboard |  1  |   $12
| 4  | G-01        | Cable    |  1  |   $1
| 5  | G-02        | Headset  |  1  |   $20

预期结果:

| Group | Item Name | Qty | Price/qty | Price Total/item | Price Total/group
| G-01  | Mouse     |  1  | $5        | $5               | $30
|       | Keyboard  |  2  | $12       | $24              | 
|       | Cable     |  1  | $1        | $1               | 
| G-02  | Headset   |  1  | $20       | $20              | $20

我已经尝试了很多天了，但还是没有解决。提前致谢。

Answer 1

您可以使用简单的 IF 和 uservar 来完成此操作，如下查询:

SELECT 
    IF(g.gname = @myg, '', @myg:= gname) AS gname,
    g.mytext
FROM grouptab g
CROSS JOIN ( SELECT   @myg:='') AS init
ORDER BY g.gname;

示例

MariaDB [test]> select * from grouptab;
+----+-------+---------+
| id | gname | mytext  |
+----+-------+---------+
|  1 | G01   | Name 1  |
|  2 | G01   | Name 2  |
|  3 | G02   | Name 88 |
|  4 | G02   | Name 99 |
|  5 | G01   | Name 4  |
+----+-------+---------+
5 rows in set (0.000 sec)

MariaDB [test]> SELECT
    ->     IF(g.gname = @myg, '', @myg:= gname) AS gname,
    ->     g.mytext
    -> FROM grouptab g
    -> CROSS JOIN ( SELECT   @myg:='') AS init
    -> ORDER BY g.gname;
+-------+---------+
| gname | mytext  |
+-------+---------+
| G01   | Name 1  |
|       | Name 2  |
|       | Name 4  |
| G02   | Name 88 |
|       | Name 99 |
+-------+---------+
5 rows in set (0.000 sec)

MariaDB [test]>