MySQL中可以用进行cast(x AS type)累进行数据转换：

sql = "SELECT SUM(costMoney)  FROM user_cost WHERE companyId = 1 AND districtId = 2  "
>>>((Decimal('14450.00'),),)
sql = "SELECT cast(SUM(costMoney) AS CHAR) FROM user_cost WHERE companyId = 1 AND districtId = 2  "
>>>((('14450.00'),),)
可转换的type：
CHAR[(N)] 字符型