获得带有varchar字段中数值的最大值的 MySQL 查询?
要获得最大值,请使用 max() 函数。让我们先创建一个表 -
mysql> create table findMaxValueInVarcharField -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value varchar(200) -> ); Query OK, 0 rows affected (1.09 sec)
以下是用 insert 命令在表中插入一些记录的查询 -
mysql> insert into findMaxValueInVarcharField(Value) values('200'); Query OK, 1 row affected (0.14 sec) mysql> insert into findMaxValueInVarcharField(Value) values('1000'); Query OK, 1 row affected (0.25 sec) mysql> insert into findMaxValueInVarcharField(Value) values('899474'); Query OK, 1 row affected (0.18 sec) mysql> insert into findMaxValueInVarcharField(Value) values('39474'); Query OK, 1 row affected (0.15 sec) mysql> insert into findMaxValueInVarcharField(Value) values('4958'); Query OK, 1 row affected (0.12 sec)
以下是用 select 语句从表中显示所有记录的查询 -
mysql> select * from findMaxValueInVarcharField;
它将产生以下输出 -
+----+--------+ | Id | Value | +----+--------+ | 1 | 200 | | 2 | 1000 | | 3 | 899474 | | 4 | 39474 | | 5 | 4958 | +----+--------+ 5 rows in set (0.00 sec)
以下是在 varchar 字段中从数值中获取最大值的查询 -
mysql> select max(cast(Value as unsigned) ) AS MaximumValueFromVarcharField from findMaxValueInVarcharField;
它将产生以下输出 -
+------------------------------+ | MaximumValueFromVarcharField | +------------------------------+ | 899474 | +------------------------------+ 1 row in set (0.00 sec)
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