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MySQL查询跳过重复项并从重复值中仅选择一个

2024-04-30 12:18:05 406

语法如下所示，以跳过重复值并仅从重复值中选择一个-

select min(yourColumnName1),yourColumnName2 from yourTableName group by
yourColumnName2;

为了理解上述语法，让我们创建一个表。创建表的查询如下-

mysql> create table doNotSelectDuplicateValuesDemo
   -> (
   -> User_Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   -> User_Name varchar(20)
   -> );

现在，您可以使用insert命令在表中插入一些记录。查询如下-

mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('John');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Carol');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Carol');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Carol');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Sam');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Mike');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Bob');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('David');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Maxwell');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Bob');
mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('Ramit');

使用select语句显示表中的所有记录。查询如下-

mysql> select *from doNotSelectDuplicateValuesDemo;

这是输出-

+---------+-----------+
| User_Id | User_Name |
+---------+-----------+
| 1       | John      |
| 2       | Carol     |
| 3       | Carol     |
| 4       | Carol     |
| 5       | Sam       |
| 6       | Mike      |
| 7       | Bob       |
| 8       | David     |
| 9       | Maxwell   |
| 10      | Bob       |
| 11      | Ramit     |
+---------+-----------+
11 rows in set (0.00 sec)

这是跳过重复值并仅从重复值中选择一个的查询-

mysql> select min(User_Id),User_Name from doNotSelectDuplicateValuesDemo group by
User_Name;

这是输出-

+--------------+-----------+
| min(User_Id) | User_Name |
+--------------+-----------+
| 1            | John      |
| 2            | Carol     |
| 5            | Sam       |
| 6            | Mike      |
| 7            | Bob       |
| 8            | David     |
| 9            | Maxwell   |
| 11           | Ramit     |
+--------------+-----------+
8 rows in set (0.07 sec)

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MySQL查询跳过重复项并从重复值中仅选择一个

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