如何在SQL中将Varchar转换为Double？
您可以使用CAST()函数将varchar转换为double。语法如下：
SELECT yourColumnName1,yourColumnName2,......N, CAST(yourColumnName AS DECIMAL(TotalDigit,DigitAfterDecimalPoint)) anyVariableName FROM yourtableName ORDER BY anyVariableName DESC;
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 VarcharToDouble -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(10), -> Amount varchar(10) , -> PRIMARY KEY(Id) -> );
使用insert命令在表中插入一些记录。查询如下：
mysql> insert into VarcharToDouble(Name,Amount) values('John','456.78');
mysql> insert into VarcharToDouble(Name,Amount) values('Larry','8465.98');
mysql> insert into VarcharToDouble(Name,Amount) values('Mike','9083.45');
mysql> insert into VarcharToDouble(Name,Amount) values('Sam','46475.50');
mysql> insert into VarcharToDouble(Name,Amount) values('Carol','10003.35');使用select语句显示表中的所有记录。查询如下：
mysql> select *from VarcharToDouble;
以下是输出：
+----+-------+----------+ | Id | Name | Amount | +----+-------+----------+ | 1 | John | 456.78 | | 2 | Larry | 8465.98 | | 3 | Mike | 9083.45 | | 4 | Sam | 46475.50 | | 5 | Carol | 10003.35 | +----+-------+----------+ 5 rows in set (0.00 sec)
这是使用以下命令将varchar转换为double的查询CAST()：
mysql> select Id,Name, CAST(Amount AS DECIMAL(10,2)) TotalAmount from VarcharToDouble -> order by TotalAmount desc;
以下是输出：
mysql> select Id,Name, CAST(Amount AS DECIMAL(10,2)) TotalAmount from VarcharToDouble -> order by TotalAmount desc;