mysql - 嵌套 CAST 不起作用

Question

为什么嵌套转换在 MySQL 中不起作用？（它确实使用 SQL Server）

select cast(cast(myColumn as decimal(5,2)) as int) from myTable 

SQLFiddle 示例

Answer 1

根据手册：

CAST(expr AS type)[...]

CONVERT(expr,type)[...]

type可以是以下值之一：

• BINARY[(N)]

• CHAR[(N)]

• DATE

• DATETIME

• DECIMAL[(M[,D])]

• SIGNED [INTEGER]

• TIME

• UNSIGNED [INTEGER]

因此，只需按照手册进行操作：

SELECT CAST(CAST(myColumn AS DECIMAL(5,2)) AS SIGNED) FROM myTable

或者

SELECT CAST(CAST(myColumn AS DECIMAL(5,2)) AS UNSIGNED) FROM myTable

Answer 2

此查询正在处理嵌套转换的概念。

cast(sum(cast(Column_name int)+ cast(Column_name as int)) as bigint) 作为来自 table_name 的付款