如何查询VARCHAR和int

Question

我有这个表

name | prof  |grade 
------------------------ 
yossi math  100 
tami math  70 
yossi phisic 100 
tami phisic 100 
oren math  100 
oren phisic 80 
dor  history 70 

查询应返回学生的名字已在数学100级和phisic 正确unswer是贝纳 我用下面的

SELECT name FROM [dbo].[Class_grade] 
where prof in ('math', 'phisic') and grade = 100 

但它返回更多的名字为什么？ 什么是正确的查询？ 感谢

Answer 1

试试这个：

SELECT DISTINCT name FROM [dbo].[Class_grade] where prof in ('math', 'phisic') and grade = 100 

这会工作，以及：

SELECT DISTINCT name FROM [dbo].[Class_grade] where (prof = 'math' and grade = 100) OR (prof = 'phisics' and grade = 100) 

Answer 2

早些时候，我错误地引用了Question

您可以使用Group by caluse

SELECT name FROM [Class_grade] 
where prof in ('math', 'phisic') and grade = 100 
group by (name) 
having count(1)=2 

SQL FIDDLE

Answer 3

select name 
from Class_Grade 
where grade = 100 and 
     prof in ('math', 'phisic') 
group by name 
having count(distinct prof) = 2 

组通过name和使用having过滤掉的行。确保你计算了prof的不同事件。在这种情况下，它是2，因为你的in子句中有2个值。

Answer 4

组通过，并suure你两行

SELECT name 
FROM Class_grade 
WHERE prof in ('math', 'phisic') and grade = 100 
GROUP BY name 
HAVING count(*) = 2 

http://www.sqlfiddle.com/#!3/9308c/6

编辑 你可以抓住不同的等级，如果同样的学生可以在主题有一个以上的100％

SELECT name 
FROM (
    SELECT DISTINCT name, prof, grade 
    FROM Class_grade 
    WHERE prof in ('math', 'phisic') and grade = 100 
) class_grade 
GROUP BY name 
HAVING count(*) = 2 

http://www.sqlfiddle.com/#!3/79fd0/11

Answer 5

试试这个

SELECT name FROM Class_grade 
WHERE prof IN ('math', 'phisic') AND grade=100 
GROUP BY name 
HAVING COUNT(name) > 1 

Answer 6

的OP未说明几个细节：

• 关于什么是表的主键（即可以为同一学科的同一名学生存在多行）
• 当有多个学生符合条件时，预期结果如何。

如果我们假设一个学生在同一个科目中可以有多个成绩，其他许多答案在HAVING COUNT(*)条款中都是错误的。Mikael Eriksson's answer满足这个假设，它可能比我下面的解决方案更好的性能（虽然功能不同的有点太）：

SELECT DISTINCT name FROM [dbo].[Class_grade] cg1 
WHERE EXISTS (
    SELECT 1 FROM [dbo].[Class_grade] cg2 
    WHERE cg2.name = cg1.name 
    AND cg2.prof = 'math' 
    AND cg2.grade = 100) 
AND EXISTS (
    SELECT 1 FROM [dbo].[Class_grade] cg2 
    WHERE cg2.name = cg1.name 
    AND cg2.prof = 'phisic' 
    AND cg2.grade = 100) 
AND NOT EXISTS (
    SELECT 1 FROM [dbo].[Class_grade] cg2 
    WHERE cg2.name = cg1.name 
    AND cg2.prof in ('math','phisic') 
    AND cg2.grade < 100) 

在上面的代码不同的是，它只会选择只有grade = 100了谁的学生math和phisic科目，即使他们每个科目可以有不止一个年级。 See here。

Answer 7

  select Class_grade.name 
      from Class_grade 
      inner join Class_grade Class_grade2 
      on Class_grade.Name = Class_grade2.name 
      where Class_grade.Prof = 'math' and Class_grade.grade = 100 
      and Class_grade2.prof = 'phisic' and Class_grade2.grade = 100 
      group by Class_grade.Name 

尽量不要使用不同的，它是一个糟糕的编码