Question

Suppose I have columns col1, col2, col3, col4 in myTable and I need to print out the values exclusive to only one column .

So if the above looks like

  col1    col2    col3    col4
  s        e       c        b 
  c        c       a        s
  n        s       e        a
  d        d       q        c

Then the output should be n, q b since they are exclusive only to col1, col3 and col4 respectively.

How can I achieve this through a query in mysql php?

EDIT The duplicates dont have to be in a single row .I have changed the the table layout now to make it clear.

Answer 1

If you are looking for a SQL-only solution, you can do a query per column like this:

SELECT 
    col1 AS unique_on_col1
FROM table
WHERE     col1 NOT IN (SELECT col2 FROM table)
      AND col1 NOT IN (SELECT col3 FROM table)
      AND col1 NOT IN (SELECT col4 FROM table)

It’s possible to combine all four queries with UNION but that may not be necessary depending on what you want to do with the data. Also, this query should not perform very well with large datasets.