Query using three terms in SQL/PHP - php

Question

I'm using WordPress, but this question is more pertaining to the SQL involved. I'll gladly move it if I need to.
I'm working on http://www.libertyguide.com/jobs and I'm trying to alter the filtering mechanics. Currently it's a global OR query.
Anyways, I have three filtering lists, and I'm storing what's selected into three strings (interests, type, experience) in the following way:
"( $wpdb->terms.slug = 'webdevelopment' OR $wpdb->terms.slug = 'journalism' OR ... ) AND"
It's populated by whatever is selected in my filtering lists.
When it comes down to it, I have this as a basic query (I'm leaving out the LEFT JOINS):
Before:
SELECT * FROM $wpdb->posts WHERE ($wpdb->terms.slug = 'fromlist1'
OR $wpdb->terms.slug = 'fromlist2' OR $wpdb->terms.slug = 'fromlist3')
AND $wpdb->term_taxonomy.taxonomy = 'jobtype'...
After:
SELECT * FROM $wpdb->posts WHERE
($wpdb->terms.slug = 'fromlist1' OR $wpdb->terms.slug = 'fromlist1again')
AND ($wpdb->terms.slug = 'fromlist2' OR $wpdb->terms.slug = 'fromlist2again')
AND ($wpdb->terms.slug = 'fromlist3' OR $wpdb->terms.slug = 'fromlist3again')
AND $wpdb->term_taxonomy.taxonomy = 'jobtype'...
So essentially I want to go from an
OR filter
to
an AND filter with OR filtering inbetween.
My new filtering only works when one item overall is selected, but returns nothing when I select more than one thing (that I know would match up with a few posts).
I've thought through the logic and I don't see anything wrong with it. I know nothing is wrong with anything else, so it has to be the query itself.
Any step in the right direction would be greatly appreciated. Thanks!
UPDATE
From the confusion, basically I have this:
"SELECT ...... WHERE $terms ..."
but I WANT
"SELECT ....... WHERE $interests AND $type AND $experience"
I don't want to have it filter $interest[1] OR $interest[2] OR $type[1] OR $experience[1], but instead want it to filter ($interest[1] OR $interest[2]) AND ($type[1]) AND ($experience[1])
I hope this makes more sense
*UPDATE 2*
Here's and example:
In my interests list, I select for example three things: WebDevelopment, Academia, Journalism.
In my type list, I choose two things: Fulltime, Parttime
In my experience list, I choose three things: Earlycareer, Midcareer, Latecareer.
When I run my query, I want to make sure that each record has AT LEAST one of each of the three lists. Possible Results: (WebDevelopment, Parttime, Midcareer), (Academia, Fulltime, Earlycareer, Midcareer).
NOT A RESULT: (Journalism, Earlycareer) - missing fulltime or parttime
I really hope this clears it up more. I'm willing to give compensation if I can get this working correctly.

Answer 1

Okay, I'll take a shot at this:
SELECT * FROM $wpdb->posts WHERE
(
$wpdb->terms.slug IN ('$interest1', '$interest2') AND
$wpdb->terms.slug IN ('$type1', '$type2') AND
$wpdb->terms.slug IN ('$exp1', '$exp2')
)
AND $wpdb->term_taxonomy.taxonomy = 'jobtype'
The IN keyword will return true if any member of the set matches.

Answer 2

I think you're looking for a WHERE category IN (comma, seperated, list, of, values) that you can generate dynamically from the form. If you combine it with the other categories, you can require them to select something from each with...
WHERE category1 IN (a, comma, seperated, list, of, values)
AND category2 IN (another, list, of, values)
AND ...
Which will only return a value if there is something selected from each category and will return nothing if any of the selection lists are empty; actually it may well kick out an error, so I would also generate the query dynamically if there is any content whatsoever for a given category.
if (!empty($arrayOfCategory1)) {
//sanitize input logic here
$Category[1] = 'category1 IN ('. implode(', ', $arrayOfCategory1) .')';
} else {
$Category[1] = '';
}
You concatenate the resultant string together and build the query with that. The WHERE 1=1 trick is problematic because if nothing is chosen, everything in the database will match, so I strongly recommend going through the process of adding the AND operators properly.
EDIT: it occurs to me that if you build the conditional statements as an array, you can implode those with ' AND ' and get the query in a fairly small number of lines of code.

Answer 3

Sort of confused a bit by what you are saying but if I wanted to build a filter I would be dynamically generating the SQL query based on the submitted filter values. Something like:
$sql = "SELECT * FROM $wpdb->posts WHERE 1=1";
if ( !empty($interest) ) { // they ticked the interested in ??? checkbox
$sql .= " AND $wpdb->terms.slug = $interest"
}
Obviously you will need to filter and escape any values that have been submitted.