Selecting values present in one column but not in all other columns - php

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.

Answer 2

One slightly more compact way of getting all of them at once:
select distinct col1
from myTable
where col1 not in (select a.col1
from myTable a join myTable b
on a.col1 = b.col2 or a.col1=b.col3 or a.col1=b.col4)
union
select distinct col2
from myTable
where col2 not in (select a.col2
from myTable a join myTable b
on a.col2 = b.col1 or a.col2=b.col3 or a.col2=b.col4)
union
select distinct col3
from myTable
where col3 not in (select a.col3
from myTable a join myTable b
on a.col3 = b.col1 or a.col3=b.col2 or a.col3=b.col4)
union
select distinct col4
from myTable
where col4 not in (select a.col4
from myTable a join myTable b
on a.col4 = b.col1 or a.col4=b.col2 or a.col4=b.col3)

Answer 3

$sql = "
SELECT DISTINCT 'col1' as descr,col1 as val FROM myTable
UNION
SELECT DISTINCT 'col2' as descr,col2 as val FROM myTable
UNION
SELECT DISTINCT 'col3' as descr,year as val FROM myTable";
$result = #mysql_query($sql, $con) or die(mysql_error());
while($row = mysql_fetch_array($result)) {
$make_array[$row['descr']][]=$row['val'];
}
I'm guessing this should work. Dint try the code out but give this one a shot and let us know.

Answer 4

Try 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)