要在MySQL中僅傳回一次列值，我們首先來看一個示例并建立一個表-create table DemoTable680(Status varchar(100));
使用插入指令在表中插入一些記錄-insert into DemoTable680 values('Busy');
insert into DemoTable680 values('At Work');
insert into DemoTable680 values('Busy');
insert into DemoTable680 values('Blocked');
insert into DemoTable680 values('Offline');
insert into DemoTable680 values('Offline');
insert into DemoTable680 values('Blocked');
使用select語句顯示表中的所有記錄-select *from DemoTable680;
這将産生以下輸出-+---------+
| Status |
+---------+
| Busy |
| At Work |
| Busy |
| Blocked |
| Offline |
| Offline |
| Blocked |
+---------+
7 rows in set (0.00 sec)
以下是在MySQL中僅傳回一次重複列值的查詢-select distinct Status from DemoTable680 order by Status;
這将産生以下輸出-+---------+
| Status |
+---------+
| At Work |
| Blocked |
| Busy |
| Offline |
+---------+
4 rows in set (0.00 sec)