3.3.4.3 选择特定列
如果不想看到表中的整行，只需命名感兴趣的列，用逗号分隔即可。例如，如果你想知道动物的出生时间，请选择 name 和 birth 列：
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 |
+----------+------------+
要查找谁拥有宠物，请使用以下查询：
mysql> SELECT owner FROM pet;
+--------+
| owner |
+--------+
| Harold |
| Gwen |
| Harold |
| Benny |
| Diane |
| Gwen |
| Gwen |
| Benny |
| Diane |
+--------+
请注意，查询只是从每个记录中检索所有者列，其中一些记录出现多次。要最小化输出，请通过添加关键字 DISTINCT 检索每个唯一的输出记录一次：
mysql> SELECT DISTINCT owner FROM pet;
+--------+
| owner |
+--------+
| Benny |
| Diane |
| Gwen |
| Harold |
+--------+
可以使用 WHERE 子句组合行选择和列选择。例如，要仅获取狗和猫的出生日期，请使用以下查询：
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 |
+--------+---------+------------+