MySQL Sum() multiple columns

Question

I have a table of student scorecard. here is the table,

subject  | mark1 | mark2 | mark3 |......|markn
stud1    | 99    | 87    | 92    |      | 46
stud2            


        

Answer 1

SELECT student, (SUM(mark1)+SUM(mark2)+SUM(mark3)....+SUM(markn)) AS Total
 FROM your_table
 GROUP BY student

Answer 2

The short answer is there's no great way to do this given the design you have. Here's a related question on the topic: Sum values of a single row?

If you normalized your schema and created a separate table called "Marks" which had a subject_id and a mark column this would allow you to take advantage of the SUM function as intended by a relational model.

Then your query would be

SELECT subject, SUM(mark) total 
FROM Subjects s 
  INNER JOIN Marks m ON m.subject_id = s.id
GROUP BY s.id

Answer 3

Another way of doing this is by generating the select query. Play with this fiddle.

SELECT CONCAT('SELECT ', group_concat(`COLUMN_NAME` SEPARATOR '+'), ' FROM scorecard') 
FROM  `INFORMATION_SCHEMA`.`COLUMNS` 
WHERE `TABLE_SCHEMA` = (select database()) 
AND   `TABLE_NAME`   = 'scorecard'
AND   `COLUMN_NAME` LIKE 'mark%';

The query above will generate another query that will do the selecting for you.

1. Run the above query.
2. Get the result and run that resulting query.

Sample result:

SELECT mark1+mark2+mark3 FROM scorecard

You won't have to manually add all the columns anymore.

Answer 4

If any of your markn columns are "AllowNull" then you will need to do a little extra to insure the correct result is returned, this is because 1 NULL value will result in a NULL total.

This is what i would consider to be the correct answer.

SUM(IFNULL(`mark1`, 0) + IFNULL(`mark2`, 0) + IFNULL(`mark3`, 0)) AS `total_marks` 

IFNULL will return the 2nd parameter if the 1st is NULL. COALESCE could be used but i prefer to only use it if it is required. See What is the difference bewteen ifnull and coalesce in mysql?

SUM-ing the entire calculation is tidier than SUM-ing each column individually.

SELECT `student`, SUM(IFNULL(`mark1`, 0) + IFNULL(`mark2`, 0) + IFNULL(`mark3`, 0)) AS `total_marks` 
FROM student_scorecard
GROUP BY `student`

Answer 5

SELECT student, SUM(mark1+mark2+mark3+....+markn) AS Total FROM your_table

Answer 6

You could change the database structure such that all subject rows become a column variable (like spreadsheet). This makes such analysis much easier