#### 3.3.4.3 选择指定列 如果你不想看到表中的所有行, 只需要用逗号分隔感兴趣的列. 例如, 如果你想知道你的动物是什么是时候出生的, 选择 `name` 和 `birth` 列: ```sql mysql> SELECT name, birth FROM pet; +----------+------------+ | name | birth | +----------+------------+ | Fluffy | 1993-02-04 | | Claws | 1994-03-17 | | Buffy | 1989-05-13 | | Fang | 1990-08-27 | | Bowser | 1989-08-31 | | Chirpy | 1998-09-11 | | Whistler | 1997-12-09 | | Slim | 1996-04-29 | | Puffball | 1999-03-30 | +----------+------------+ ``` 要了解谁拥有宠物, 使用以下查询: ```sql mysql> SELECT owner FROM pet; +--------+ | owner | +--------+ | Harold | | Gwen | | Harold | | Benny | | Diane | | Gwen | | Gwen | | Benny | | Diane | +--------+ ``` 注意, 查询只是从每条记录中检索 `owner` 列, 其中某些记录不止出现一次. 要最小化输出, 只徐通过添加 `DISTINCT` 关键词一次检索处每个唯一的输出记录: ```sql mysql> SELECT DISTINCT owner FROM pet; +--------+ | owner | +--------+ | Benny | | Diane | | Gwen | | Harold | +--------+ ``` 你可以使用 `WHERE` 子句组合记录选择和列选择. 例如, 仅仅获取猫狗的出生日期, 使用以下查询: ```sql mysql> SELECT name, species, birth FROM pet WHERE species = 'dog' OR species = 'cat'; +--------+---------+------------+ | name | species | birth | +--------+---------+------------+ | Fluffy | cat | 1993-02-04 | | Claws | cat | 1994-03-17 | | Buffy | dog | 1989-05-13 | | Fang | dog | 1990-08-27 | | Bowser | dog | 1989-08-31 | +--------+---------+------------+ ```