Oracle multi table query

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One 、 Link query

1、 Query student information and teacher information , And among the students id, And teachers sid equal .

select * from student,teacher where student.id = teacher.sid;

2、 Check student name and teacher name , And among the students id, And teachers sid equal .

select s.name,t.name from student s,teacher.t where s.id = t.sid;

3、 Check student name and teacher name , And among the students id, And teachers sid Use left join query .

select s.name,t.name from student s left join teacher t on s.id = t.sid;

4、 Check student name and teacher name , And among the students id, And teachers sid Use right join query .

select s.name,t.name from student s right join teacher t on s.id = t.sid;

5、 Check student name and teacher name , And among the students id, And teachers sid Use inner link query .

select s.name,t.name from student s inner join teacher t on s.id = t.sid;

Two 、 Data collection operations

intersection 、 Combine 、 Difference set 、 Complement set

1、 Query all student information and student name as “ Zhang San ” Student information , If repeated, remove the repeated .

select * from student 
union
select * from student where name = ' Zhang San ';

2、 Query all student information and student name as “ Zhang San ” Student information , If the repetition is also displayed .

select * from student 
union all
select * from student where name = ' Zhang San ';

3、 Query all student information and student name as “ Zhang San ” The intersection of student information , If there is intersecting information, you can find it .

select * from student
intersect
select * from student where name = ' Zhang San ';

4、 Query all student information and student name as “ Zhang San ” Difference set of student information based on （ The difference set is the information one party has and the other party does not have ）.

select * from student
minus
select * from student where name = ' Zhang San ';

3、 ... and 、 summary

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The commands involved in the article must be typed several times each like me , Only in the process of knocking can you find out whether you really master the command .

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