Insert sum of the row data of each record into separate column in postgreSQL? I have a table 

   id   name     class  social  science math  Total
    2   Max      Three  85        56     85
    3   Arnold   Three  55        40     75
    4   Krish    Four   60        50     70
    5   John     Four   60        80     90


I have to find total of each student's marks and insert to column Total.

While running this query -

INSERT INTO student(Total)    
SELECT (social + math + science ) as Total from student;


I am getting in this format -

   id   name     class  social  science math  Total
    2   Max      Three  85        56     85
    3   Arnold   Three  55        40     75
    4   Krish    Four   60        50     70
    5   John     Four   60        80     90
    6                                          226
    7                                          170
    8                                          180
    9                                          230


How to correct this I am not getting.
Use an UPDATE statement. 

update student 
   set total = social + math + science;


But that column is totally useless. In general you should not store data in a database that can easily be derived from existing values. 

In your, adding the values of the three columns adds no (noticeable) overhead to a select statement, so there is no point in storing the total. 

You should rather remove the column completely and then create a view doing this for you. Otherwise you need to update that column each time one of the other three columns are changed. 

create view total_score
as
select id, name, class, social, science, math, 
       social + math + science as total
from student;




Plus: your name column should be defined as NOT NULL.