How to update One table column values ​​with other table column values?

Question

I have a table called Student with columns uniquename, age, department, city, Homecountry and another table called Employee with columns uniquename, exp, qualification, Homecountry.

now I want to update the column column column of the table with the qualification columns of the Employee table, where the condition Student.uniquename = Employee.uniquename and Student.Homecountry = Employee.Homecountry.

please help me write an update expression.

Answer 1

This type of query is called a correlated subquery. For your requirement, the request will be as below.

update students s
  set s.department = (
          select e.qualification
            from employee e
            where s.uniquename = e.uniquename 
              and s.Homecountry = e.Homecountry
       );

.

, , create ( ) . erro , , " ". sqlplus.

---

create table student(
     name varchar2(20),
     age  number,
     department varchar2(3),
     HomeCountry varchar2(10)
    );

Table created.

create table employee5(
     name varchar2(20),
     exp  number,
     qualification varchar2(3),
     homecountry varchar2(10)
   );

Table created.

insert into student values ('Mohan',25,'EEE','India');
insert into student values ('Raja',27,'EEE','India');
insert into student values ('Ahamed',26,'ECE','UK');
insert into student values ('Gokul',25,'IT','USA');
commit;

insert into employee5 values ('Mohan',25,'ECE','India');
insert into employee5 values ('Raja',24,'IT','India');
insert into employee5 values ('Palani',26,'ECE','USA');
insert into employee5 values ('Sathesh',29,'CSE','CANADA');
insert into employee5 values ('Ahamed',28,'ECE','UK');
insert into employee5 values ('Gokul',29,'EEE','USA');
commit;

...

SQL> select * from student;

NAME                        AGE DEP HOMECOUNTR
-------------------- ---------- --- ----------
Mohan                        25 EEE India
Raja                         27 EEE India
Ahamed                       26 ECE UK
Gokul                        25 IT  USA

SQL> select * from employee5;

NAME                        EXP QUA HOMECOUNTR
-------------------- ---------- --- ----------
Mohan                        25 ECE India
Raja                         24 IT  India
Palani                       26 ECE USA
Sathesh                      29 CSE CANADA
Ahamed                       28 ECE UK
Gokul                        29 EEE USA

  1  update student s set s.age =
  2     ( select e.exp
  3          from employee5 e
  4          where e.name = s.name
  5            and e.homecountry = s.homecountry
  6*    )
SQL> /

4 rows updated.

SQL> select * from student;

NAME                        AGE DEP HOMECOUNTR
-------------------- ---------- --- ----------
Mohan                        25 EEE India
Raja                         24 EEE India
Ahamed                       28 ECE UK
Gokul                        29 IT  USA

SQL> commit;

Commit complete.

Answer 2

update student s 
   set s.age = (select e.exp 
                  from employee5 e 
                  where e.name = s.name 
                    and e.homecountry = s.homecountry  
                    and rownum < 2
               )
where s.age in (select age from employee5)

,