有你，查询数据我什么都不怕。有种尽管来啊！快快掌握！！出大招的工具：1.使用LIKE、BETWEEN、IN进行模糊查询eg1:SELECT * FROM StudentsWHERE 姓名 like 张%eg2:SELECT StudentID, Score FROM SCor ...
有你，查询数据我什么都不怕。有种尽管来啊！快快掌握！！
出大招的工具：
1.使用LIKE、BETWEEN、IN进行模糊查询
eg1:
SELECT * FROM Students
WHERE 姓名 like '张%'
eg2:
SELECT StudentID, Score FROM SCore WHERE Score
BETWEEN 60 AND 80
eg3:
SELECT SName AS 学生姓名,SAddress AS 地址
FROM Students
WHERE SAddress IN ('北京','广州','上海')
2.通配符
eg:
SELECT * FROM 数据表
WHERE 编号 LIKE '00[^8]%[AC]%'
3.SUM()
AVG()
MAX()、MIN()
COUNT()
eg1:
SELECT SUM(Score) AS 学号为23的学生总分
FROM Score
WHERE StudentID =23
eg2:
SELECT AVG(SCore) AS 及格平均成绩
FROM Score
WHERE Score >=60
eg3:
SELECT AVG(SCore) AS 平均成绩, MAX (Score) AS 最高分,
MIN (Score) AS 最低分
FROM Score
WHERE Score >=60
eg4:
SELECT COUNT (*) AS 及格人数
FROM Score
WHERE Score>=60
4.分组查询用法
SELECT …… FROM <表名>
WHERE ……
GROUP BY ……
eg:
SELECT COUNT(*) AS 人数, SGrade AS 年级
FROM Students
GROUP BY SGrade
eg2:
SELECT CourseID, AVG(Score) AS 课程平均成绩
FROM Score
GROUP BY CourseID
eg3:
SELECT CourseID, AVG(Score) AS 课程平均成绩
FROM Score
GROUP BY CourseID
ORDER BY AVG(Score)
5.多列分组
SELECT COUNT(*) AS 人数,SGrade AS 年级,SSex AS 性别
FROM StudentS
GROUP BY SGrade,SSex
ORDER BY SGrade
6.分组筛选
SELECT …… FROM <表名>
WHERE ……
GROUP BY ……
HAVING……
eg:
SELECT COUNT(*) AS 人数,SGrade AS 年级
FROM Students
GROUP BY SGrade
HAVING COUNT(*)>15
7.多表连接查询
内连接(INNER JOIN)
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