[SQL] 查询不相同的记录

SQL 语法这样用: SELECT DISTINCT owner FROM pet;

参考文档:

找出谁拥有宠物，使用这个查询：

mysql> SELECT owner FROM pet;
+--------+
| owner  |
+--------+
| Harold |
| Gwen   |
| Harold |
| Benny  |
| Diane  |
| Gwen   |
| Gwen   |
| Benny  |
| Diane  |
+--------+

然而，注意到查询简单地检索每个记录的owner字段，并且他们中的一些出现多次。为了使输出减到最少，通过增加关键词DISTINCT检索出每个唯一的输出记录：

mysql> SELECT DISTINCT owner FROM pet;
+--------+
| owner  |
+--------+
| Benny  |
| Diane  |
| Gwen   |
| Harold |
+--------+

参考自: http://www.moon-soft.com/program/book/mysql/manual_Tutorial.html#Entering_queries