Explain MERGE Statement in SQL ?

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

Ex: 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);