How to SUM multiple fields with condition

Here is my table structure

id  col1  col2  col3  col4
1       1     1     2     1

the thing is, i want to SUM field (col1,col2,col3,col4) but only the value 1. so based on the record above. the result would be 3 (col1+col2+col4), becauser value from col3 is 2 not 1.

sorry for bad grammar.

Answer

Either you mean:

1. You want to calculate a new column on each row which is the sum of columns 1 through 4 if those columns are 1 (which is the same as the count of columns which are 1), or
2. You want to calculate the sum of those columns but only when the row values of those columns are 1

For 1:

SELECT id, col1, col2, col3, col4
, CASE WHEN col1 = 1 THEN 1 ELSE 0 END
  + CASE WHEN col2 = 1 THEN 1 ELSE 0 END
  + CASE WHEN col3 = 1 THEN 1 ELSE 0 END
  + CASE WHEN col4 = 1 THEN 1 ELSE 0 END
AS row_count_of_ones
FROM table_name;

For 2:

SELECT SUM(
    CASE WHEN col1 = 1 THEN 1 ELSE 0 END
  + CASE WHEN col2 = 1 THEN 1 ELSE 0 END
  + CASE WHEN col3 = 1 THEN 1 ELSE 0 END
  + CASE WHEN col4 = 1 THEN 1 ELSE 0 END
     ) AS count_of_ones
FROM table_name;