使用 MySQL 选择语句删除具有重复和相似内容的行并获取具有最大数量的行?
mysqlmysqli database更新于 2024/2/11 14:27:00
首先我们创建一个表 −
mysql> create table DemoTable1468 -> ( -> Id int, -> Name varchar(20), -> Age int -> ); Query OK, 0 rows affected (1.21 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable1468 values(100,'Chris',23); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable1468 values(101,'Bob',25); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1468 values(102,'David',30); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1468 values(100,'Chris',23); Query OK, 1 row affected (0.35 sec) mysql> insert into DemoTable1468 values(100,'Chris',38); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1468 values(101,'Bob',23); Query OK, 1 row affected (0.13 sec)
使用 select 语句显示表中的所有记录 −
mysql> select * from DemoTable1468;
这将产生以下输出 −
+------+-------+------+ | Id | Name | Age | +------+-------+------+ | 100 | Chris | 23 | | 101 | Bob | 25 | | 102 | David | 30 | | 100 | Chris | 23 | | 100 | Chris | 38 | | 101 | Bob | 23 | +------+-------+------+ 6 rows in set (0.00 sec)
以下查询用于删除具有重复和相似内容的行，并使用 select 语句获取具有最大数量的行 −
mysql> select Id,Name,Age from DemoTable1468 -> group by Name,Id -> having max(Age);
这将产生以下输出 −
+------+-------+------+ | Id | Name | Age | +------+-------+------+ | 100 | Chris | 23 | | 101 | Bob | 25 | | 102 | David | 30 | +------+-------+------+ 3 rows in set (0.00 sec)
