嵌套CAST不工作 [英] Nested CAST not working

问题描述

为什么一个嵌套的转换不能在MySQL中工作？ （它使用SQL Server）

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

SQLFiddle示例

解决方案

根据手册：

CAST（expr AS类型） [...]

CONVERT（expr，type） [...]

type 可以是以下值之一：

• BINARY [（N）]




• CHAR [（N）]




• DATE




• DATETIME

  
  

• DECIMAL [（M [，D]）]

  
  

• SIGNED [INTEGER] >

>

<$>

blockquote>



所以，只要按照手册：

  SELECT CAST AS DECIMAL（5,2））AS TYPE）FROM myTable 
  

或

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




Why is a nested cast NOT working in MySQL? (It does using SQL Server)

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

SQLFiddle Example

解决方案

According to the manual:

CAST(expr AS type) [...]

CONVERT(expr,type) [...]

The type can be one of the following values:

• BINARY[(N)]

• CHAR[(N)]

• DATE

• DATETIME

• DECIMAL[(M[,D])]

• SIGNED [INTEGER]

• TIME

• UNSIGNED [INTEGER]

So, just follow the manual:

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

or

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

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