作者：dmcm0008 | 来源：互联网 | 2023-10-10 22:37
c_mart_order_info 表执行
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| mysql> SELECT order_id,order_sn FROM `c_mart_order_info` WHERE `order_sn` = '16030515100000196809';
+----------+----------------------+
| order_id | order_sn |
+----------+----------------------+
| 27 | 16030515100000196809 |
+----------+----------------------+
1 row in set (0.00 sec) |
c_order_pay 执行
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| mysql> select order_sn from c_order_pay where order_sn=16030515100000196809;
+----------------------+
| order_sn |
+----------------------+
| 16030515100000196809 |
+----------------------+
1 row in set (0.00 sec) |
两个表 left join 后
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| mysql> select a.order_sn as a_sn,c.order_sn as c_sn from c_mart_order_info as a left join c_order_pay as c on a.order_sn=c.order_sn where a.order_id=27;
+----------------------+------+
| a_sn | c_sn |
+----------------------+------+
| 16030515100000196809 | NULL |
+----------------------+------+
1 row in set (0.00 sec) |
两个表都有相同的 order_sn 用left join 查询，为什么只得到一个表的信息，哪里出错了？
------更---------
感谢 woderwang 提醒，我的mysql 版本是5.1，col类型不一样造成，但是某些更新版本的mysql，却没有这个问题，
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