Question

I have this code:

mysql_query("
   SELECT id as tc_id, firstname, surname, position, @concat := CONCAT(firstname,' ',surname) 
   FROM tc 
   WHERE (@concat LIKE '%". mysql_real_escape_string($_REQUEST['search_term']) ."%');");

search_term just refers to the value of a text input.

When I run the SELECT statement in sequel pro locally – my mysql program – it works perfectly, selecting the appropriate rows. When I run the query however locally through my PHP page, it returns no rows, even though it should. Help anyone?

Answer 1

WHERE does not work on calculated columns, therefore your query, per se, will not work.

It probably works because you locally have a @concat variable declared. It will also appear to work if you run the query twice in specific conditions, because your query might actually assign a @concat variable.

What you want is

SELECT id as tc_id, firstname, surname, position,
    CONCAT(firstname,' ',surname)  AS concat
FROM tc HAVING concat LIKE '%<YOUR SEARCH TERM>%';

As test:

-- Declare a minimum table to match the query
CREATE TABLE tc (id integer, firstname varchar(20), surname varchar(20), position integer);

INSERT INTO tc (firstname, surname) VALUES ('alfa', 'bravo');

-- Your query...

SELECT id as tc_id, firstname, surname, position,
    @concat := CONCAT(firstname,' ',surname) FROM tc WHERE (@concat LIKE '%alfa%');

-- ...returns nothing

Empty set (0.00 sec)

-- The proper query works.

SELECT id as tc_id, firstname, surname, position, CONCAT(firstname,' ',surname)  AS concat FROM tc HAVING concat LIKE '%alfa%';
+-------+-----------+---------+----------+------------+
| tc_id | firstname | surname | position | concat     |
+-------+-----------+---------+----------+------------+
|  NULL | alfa      | bravo   |     NULL | alfa bravo |
+-------+-----------+---------+----------+------------+
1 row in set (0.00 sec)

-- But if I declare a @concat variable    

SELECT @concat := 'alfa';
+-------------------+
| @concat := 'alfa' |
+-------------------+
| alfa              |
+-------------------+
1 row in set (0.00 sec)

-- Then your query SEEMS to work.

mysql> SELECT id as tc_id, firstname, surname, position, @concat := CONCAT(firstname,' ',surname)  FROM tc  WHERE (@concat LIKE '%alfa%');
+-------+-----------+---------+----------+------------------------------------------+
| tc_id | firstname | surname | position | @concat := CONCAT(firstname,' ',surname) |
+-------+-----------+---------+----------+------------------------------------------+
|  NULL | alfa      | bravo   |     NULL | alfa bravo                               |
+-------+-----------+---------+----------+------------------------------------------+
1 row in set (0.00 sec)

-- "SEEMS" because the select query isn't actually working:

UPDATE tc SET firstname = 'delta';
Query OK, 1 row affected (0.28 sec)
Rows matched: 1  Changed: 1  Warnings: 0

-- Having renamed the only row to "delta", a search for "alpha" should fail,
-- but since @concat still holds 'alpha', then the query matches ALL rows:

mysql> SELECT id as tc_id, firstname, surname, position, @concat := CONCAT(firstname,'    ',surname)  FROM tc  WHERE (@concat LIKE '%alfa%');
+-------+-----------+---------+----------+------------------------------------------+
| tc_id | firstname | surname | position | @concat := CONCAT(firstname,' ',surname) |
+-------+-----------+---------+----------+------------------------------------------+
|  NULL | delta     | bravo   |     NULL | delta bravo                              |
+-------+-----------+---------+----------+------------------------------------------+
1 row in set (0.00 sec)