id partner_id date_created status item_id
3 2 1322861013 redirected 1
4 2 1322943245 redirected 6
5 3 1322943246 redirected 6
6 2 1322943247 redirected 6
如何计算存在相同item_id的行数?表名为orders
以上示例我希望它输出:
There's 3 rows with the item_id 6
There's 1 rows with the item_id 1
我只知道如何使用一些php循环来做这个更复杂的事情
答案 0 :(得分:2)
此处使用的模式是COUNT()
与GROUP BY
结合使用:
SELECT item_id, COUNT(id) AS item_count FROM orders GROUP BY item_id
您将获得两列可以根据需要轻松重新格式化的列。
答案 1 :(得分:1)
mysql> create table test(
-> row integer
-> ) ;
Query OK, 0 rows affected (0.05 sec)
mysql> insert into test values ( 3 ) , ( 3 ) , ( 3 ) , ( 1 ) ;
Query OK, 4 rows affected (0.00 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> select count(*) from test group by row;
+----------+
| count(*) |
+----------+
| 1 |
| 3 |
+----------+
2 rows in set (0.03 sec)
mysql>
答案 2 :(得分:0)
SELECT item_id, COUNT(id) FROM orders
GROUP BY item_id