Mysql query always returning zero

Question

PHP 7.0

Server version: 10.0.34-MariaDB-0ubuntu0.16.04.1

This is probably the strangest issue I ever encountered.

My goal is to sum the values from a table if some conditions are met ( specific type, type_no and positive value ). Amount column is of type double.

This is the query:

SELECT SUM(amount) FROM gl_trans WHERE type='0' AND type_no='1' AND amount>0;

And this is the gl_trans table - it represents the depreciation of fixed asset:

# counter, type, type_no, tran_date, event_date, doc_date, account, memo_, amount, dimension_id, dimension2_id, person_type_id, person_id
'1', '0', '1', '2018-02-28', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'2', '0', '1', '2018-02-28', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'3', '0', '1', '2018-03-31', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'4', '0', '1', '2018-03-31', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'5', '0', '1', '2018-04-30', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'6', '0', '1', '2018-04-30', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'7', '0', '1', '2018-05-31', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'8', '0', '1', '2018-05-31', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'9', '0', '1', '2018-06-30', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'10', '0', '1', '2018-06-30', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'11', '0', '1', '2018-07-31', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'12', '0', '1', '2018-07-31', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'13', '0', '1', '2018-08-31', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'14', '0', '1', '2018-08-31', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'15', '0', '1', '2018-09-30', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'16', '0', '1', '2018-09-30', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'17', '0', '1', '2018-10-31', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'18', '0', '1', '2018-10-31', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'19', '0', '1', '2018-11-30', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'20', '0', '1', '2018-11-30', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'
'21', '0', '1', '2018-12-31', '0000-00-00', '0000-00-00', '071-1-1', '', '-2', '0', '0', '6', '0001'
'22', '0', '1', '2018-12-31', '0000-00-00', '0000-00-00', '401-1', '', '2', '0', '0', '6', '0001'

So I did: (db_query and db_fetch_row are custom functions - they are 100% ok)

$sql = "SELECT SUM(amount) FROM gl_trans WHERE type=".db_escape($type)." AND type_no=".db_escape($type_no)." AND amount>0";
$result = db_query($sql, "query for gl trans total");     
$row = db_fetch_row($result);
return $row[0];

The result was null. While debuging I discovered that query for amount column... returns 0:

$sql = "SELECT amount FROM gl_trans WHERE type=".db_escape($type)." AND type_no=".db_escape($type_no);
$result = db_query($sql, "blah blah blah");
while ($test = db_fetch_assoc($result)) {
  var_dump($test); // [amount] => 0 !!!
}

I pasted the same exact query:

SELECT SUM(amount) FROM gl_trans WHERE type='0' AND type_no='1' AND amount>0

...into the Workbench and it gave me correct result (22) !

I tried to perform similar queries on different tables (just switching the table and column) and they were ok.
I also tried to sum up another field in this table (person_type_id) and the query was also successful.
Finally we have pasted the code to my coworker's laptop (same database, same system - Ubuntu, same code), and it worked.

Somehow on my computer, with my settings, just this one column in the whole database is always 0 and only if I query for it from the code.
Code is ok - it works on other tables and columns
Db is ok - queries from Workbench and console works.
I suspect some settings issue or possibly some kind of bug but I have no idea what could be wrong.

Answer 1

It looks like you are missing single quotes in your query:

$sql = "SELECT SUM(amount) FROM gl_trans WHERE type='".db_escape($type)."' AND type_no='".db_escape($type_no)."' AND amount>0";

Your code is not safe against SQL Injection. You should use PDO or prepared statements instead of the custom functions you have. Read more about it here

Checking your $sql with $var_dump() is also helpful

Answer 2

Question can be closed. The problem was elsewhere - someone mistakenly left a function hidden deep in the code that was voiding all the amounts before my function queried for them. I haven't noticed that due to transaction failure somewhere else.