Select values that are NOT in table - php

Question

Let's say I have three values in PHP: "a", "b", "c". Doesn't matter whether in an array or comma separated string.
There is a table in database:
id | value
1 | a
2 | b
3 | d
My purpose is to find the values that are in php array but not in database table.
The given example will give "c".
Can I do it with only one query?
UPDATE
Received several good suggestions in answers about array_diff(), though in my case the DB table is really large and the array has not more than 5-6 items. So it would be better to perform 5-6 queries, I think.

Answer 1

If the PHP array is short, you can build a UNION ALL query to build your small table, then use NOT IN or LEFT JOIN query (whichever is faster) against the large table:
SELECT value
FROM (
SELECT 'a' AS value
UNION ALL
SELECT 'b'
UNION ALL
SELECT 'c'
) AS php_array_values
WHERE value NOT IN (
SELECT value
FROM that_large_table
);
Alternately, you can insert the php array values in a temporary table and use the IN or JOIN queries. Of course, this means you end up writing three extra queries:
CREATE TEMPORARY TABLE IF NOT EXISTS php_array_values (value VARCHAR(100));
DELETE FROM php_array_values;
INSERT INTO php_array_values VALUES ('a'), ('b'), ('c');
SELECT php_array_values.value
FROM php_array_values
LEFT JOIN that_large_table ON php_array_values.value = that_large_table.value
WHERE that_large_table.value IS NULL

Answer 2

how about this?
<?php
$a = array('a', 'b', 'c');
$values = implode("','", $a);
$sql = "SELECT DISTINCT `value` FROM `mytable` WHERE `value` IN ('$values')";
echo $sql;
perform the sql query. the result will be those 0 to 3 elements you already have. next, do an array_diff (which will not be heavy at all, since you'll have your initial small array, and the array of those in the db, which is even smaller).
$not_in_db = array_diff($a, $array_from_sql_result);
if what you have is a string with comma separated values, then you'll need to "explode" it first:
$s = "a,b,c";
$a = explode(",", $s);

Answer 3

You could select all the entries in the table and then perform an array_diff().
But this isn't one query, is one query and some post processing.

Answer 4

For this I would pull values from the table into an array and use array_diff
REF: http://www.php.net/manual/en/function.array-diff.php

Answer 5

Instead of pulling all the elements from the DB you can try using 'LIKE' statement, this will reduce the number of entries pulled from DB.
something like this :
PHP array values : a,b,c
DB values : a,b,d
select value from your_table_name where (value LIKE '%a%') OR (value LIKE '%b%') OR (value LIKE '%c%');
o/p of this will be : {a,b}
now use array_diff of php.

Answer 6

select max(*) as count from tablename
where field1 != $arr[0] && field2 != $arr[1] && field3 != $arr[2];
You can use and or or operators if you want. if the return count for this query is 0 then the array values are not exist in the database already.