如何查詢VARCHAR和int

Question

我有這個表

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

查詢應返回學生的名字已在數學100級和phisic 正確unswer是貝納 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爲什麼？ 什麼是正確的查詢？ 感謝

Answer 1

試試這個：

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

這會工作，以及：

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

Answer 2

早些時候，我錯誤地引用了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 

組通過name和使用having過濾掉的行。確保你計算了prof的不同事件。在這種情況下，它是2，因爲你的in子句中有2個值。

Answer 4

組通過，並suure你兩行

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

編輯 你可以抓住不同的等級，如果同樣的學生可以在主題有一個以上的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

試試這個

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

Answer 6

的OP未說明幾個細節：

• 關於什麼是表的主鍵（即可以爲同一學科的同一名學生存在多行）
• 當有多個學生符合條件時，預期結果如何。

如果我們假設一個學生在同一個科目中可以有多個成績，其他許多答案在HAVING COUNT(*)條款中都是錯誤的。Mikael Eriksson's answer滿足這個假設，它可能比我下面的解決方案更好的性能（雖然功能不同的有點太）：

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) 

在上面的代碼不同的是，它只會選擇只有grade = 100了誰的學生math和phisic科目，即使他們每個科目可以有不止一個年級。 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 

儘量不要使用不同的，它是一個糟糕的編碼