Merge clause

MERGE

You can use merge command to perform insert and update in a single command.

Ex:

SQL> Merge into student1 s1

        Using (select *From student2) s2

        On(s1.no=s2.no)

        When matched then

        Update set marks = s2.marks

        When not matched then

        Insert (s1.no,s1.name,s1.marks)

        Values(s2.no,s2.name,s2.marks);

In the above the two tables are with the same structure but we can merge different structured    

tables also but the datatype of the columns should match.

Assume that student1 has columns like no,name,marks and student2 has columns like no,      

name, hno, city.

SQL> Merge into student1 s1

        Using (select *From student2) s2

        On(s1.no=s2.no)

        When matched then

        Update set marks = s2.hno

        When not matched then

        Insert (s1.no,s1.name,s1.marks)

        Values(s2.no,s2.name,s2.hno);