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In SQL, the having clause and the group by statement work together when using aggregate functions like SUM, AVG, MAX, etc. This is best illustrated by an example. Suppose we have a table called emp_bo

Answer in one line is : HAVING specifies a search condition for a group or an aggregate function used in SELECT statement. HAVING can be used only with the SELECT statement. HAVING is typically use

How to find duplicate rows with SQL This article shows how to find duplicated rows in a database table. This is a very common beginner question. The basic technique is straightforward. I’ll also

Table src: CREATE TABLE `src` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` int(11) DEFAULT NULL ) Table dest: CREATE TABLE `dest` ( `a` int(11) NOT NULL, `b` int(11) DEFAUL

关系模式： 学生（学号，姓名，系别，年龄） 课程（课程号，课程名，学时） 选读（学号，课程号，成绩） 问题：检索选读全部课程的学生姓名 select 学生.姓名 from 学生 where not exists( select * from 课程 where not exists( select * from 选读 where 学号=学生.学号 and 课程号=课程.课程号)

问题： 假如有一个表 ACCOUNT ACCOUNTID, NAME, TYPE A001， JOHN, TUTOR A002， MIKE, TUTOR A003， JIM, STUDENT A004， LILY, STUDENT 另一个表 APPOINTMENT STUDENTID, TUTORID A003, A001 A004, A002 备注：STUD