MySQL :: MySQL 8.3 Reference Manual :: 5.3.4.3 Selecting Particular Columns

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MySQL 8.3 Reference Manual / ... / Selecting Particular Columns

5.3.4.3 选择特定列

如果您不想查看整个表的行，只需指定感兴趣的列，使用逗号分隔。例如，如果您想知道动物的出生日期，选择 name 和 birth 列：

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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：

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

注意，该查询只是从每条记录中检索 owner 列，一些记录出现多次。为了最小化输出，添加关键字 DISTINCT 以检索每个唯一的输出记录：

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

您可以使用 WHERE 子句将行选择与列选择结合。例如，要获取狗和猫的出生日期，请使用以下查询：

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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 |
+--------+---------+------------+

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