如何在 MySql 存储过程中的一个 select 语句中 select 多个 avg(column)?
How to select multiple avg(column) in one select statement in MySql stored procedure?
我发现当我 select 一个 avg(column) 进入一个变量时,它是 OK.But 当我 select 多个 avg 进入一个变量时,它是 wrong.I 不想写两次,怎么解决?
//work well
SELECT
avg(MathPoint) into MathPoint
from student
where sex=1
SELECT
avg(EnglishPoint) into EnglishPoint
from student
where sex=1
//do not work
SELECT
avg(EnglishPoint) into EnglishPoint,
avg(MathPoint) into MathPoint,
from student
where sex=1
INTO
用法有语法错误。
选择字段后,INTO
应将所有变量名放在一起。
示例:
SELECT
avg(EnglishPoint), avg(MathPoint)
into EnglishPoint, MathPoint
from student
where sex=1
文档:
- SELECT ... INTO Syntax
SELECT ... INTO var_list
选择列值并将它们存储到
变量。
我发现当我 select 一个 avg(column) 进入一个变量时,它是 OK.But 当我 select 多个 avg 进入一个变量时,它是 wrong.I 不想写两次,怎么解决?
//work well
SELECT
avg(MathPoint) into MathPoint
from student
where sex=1
SELECT
avg(EnglishPoint) into EnglishPoint
from student
where sex=1
//do not work
SELECT
avg(EnglishPoint) into EnglishPoint,
avg(MathPoint) into MathPoint,
from student
where sex=1
INTO
用法有语法错误。
INTO
应将所有变量名放在一起。
示例:
SELECT
avg(EnglishPoint), avg(MathPoint)
into EnglishPoint, MathPoint
from student
where sex=1
文档:
- SELECT ... INTO Syntax
SELECT ... INTO var_list
选择列值并将它们存储到 变量。