CAST到DECIMAL在MySQL中 [英] CAST to DECIMAL in MySQL

问题描述

  CAST（（COUNT（*）* 1.5）AS DECIMAL（2））
  

我试图转换表中的行数

SQL代码：

 
 code> SELECT CONCAT（Guardian.title，''，
 Guardian.forename，''，
 Guardian.surname）AS'Guardian Name'，
 COUNT（*）AS' Number of Activities'，
（COUNT（*）* 1.5）AS'Cost'
从Schedule 
 INNER JOIN Child ON Schedule.child_id = Child.id 
 INNER JOIN Guardian ON Child.guardian = Guardian.id 
 GROUP BY Guardian 
 ORDER BY Guardian.surname，Guardian.forename ASC 
  

它产生一个错误：

 ＃1064  - 检查
对应于您的MySQL服务器版本的手册，使用正确的语法在第1行的'CAST（（COUNT（*）* 1.5）AS DECIMAL（12,2））附近使用
。
  

另一个尝试，这个强制类型也不起作用：

  SELECT CONCAT（Guardian.title，''，
 Guardian.forename，''，
 Guardian.surname）AS'Guardian Name'，
 COUNT（*）AS'Number of Activities'，
 CAST（（COUNT（*）* 1.5）AS DECIMAL（8,2））AS'cost'
 FROM Schedule 
 INNER JOIN Child ON Schedule.child_id = Child.id 
 INNER JOIN Guardian ON Child.guardian = Guardian.id 
 GROUP BY Guardian 
 ORDER BY Guardian.surname，Guardian.forename ASC 
 
 
 
 
如何使用mysql将整数转换为十进制？
解决方案
从MySQL文档： Fixed- Point Types（Exact Value） -  DECIMAL，NUMERIC ：
 
 
在标准SQL中，语法 DECIMAL （M）相当于 DECIMAL（M，0） 
 
 
所以，你转换为一个带有2位整数和0位十进制数的数字。尝试这样：
  CAST（（COUNT（*）* 1.5）AS DECIMAL（12,2））
  
 
I am trying to cast to Decimal in MySQL like this:
CAST((COUNT(*) * 1.5) AS DECIMAL(2))
I'm trying to convert the number of rows in a table (times 1.5) to a floating point number with two digits after the point.

SQL code:
 SELECT CONCAT(Guardian.title, ' ', 
               Guardian.forename, ' ', 
               Guardian.surname) AS 'Guardian Name', 
               COUNT(*) AS 'Number of Activities', 
               (COUNT(*) * 1.5) AS 'Cost'
 FROM Schedule
 INNER JOIN Child ON Schedule.child_id = Child.id
 INNER JOIN Guardian ON Child.guardian = Guardian.id
 GROUP BY Guardian
 ORDER BY Guardian.surname, Guardian.forename ASC
It produces an error:
#1064 - You have an error in your SQL syntax; check the manual that 
corresponds to your MySQL server version for the right syntax to use 
near 'CAST((COUNT(*) * 1.5) AS DECIMAL(12,2))' at line 1.
Another try, this cast also doesn't work:
 SELECT CONCAT(Guardian.title, ' ', 
               Guardian.forename, ' ', 
               Guardian.surname) AS 'Guardian Name', 
               COUNT(*) AS 'Number of Activities', 
               CAST((COUNT(*) * 1.5) AS DECIMAL(8,2)) AS 'Cost'
 FROM Schedule
 INNER JOIN Child ON Schedule.child_id = Child.id
 INNER JOIN Guardian ON Child.guardian = Guardian.id
 GROUP BY Guardian
 ORDER BY Guardian.surname, Guardian.forename ASC
How do I use mysql to cast from integer to decimal?
解决方案
From MySQL docs: Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC:

  
In standard SQL, the syntax DECIMAL(M) is equivalent to DECIMAL(M,0)
So, you are converting to a number with 2 integer digits and 0 decimal digits. Try this instead:
CAST((COUNT(*) * 1.5) AS DECIMAL(12,2)) 


                        
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