MySQL inner join two columns on one column - php

Question

I'm stuck on the inner join scenario for my tables. Can you please help me? What I am doing wrong here?
Here is the scenario that I'm trying to do:
I have billing and shipping country/states columns which I am trying to populate with inner join, but somehow it is not working. Thanks a lot for your help:
$sql = $this->connection->query("SELECT * FROM ".TBL_USERS."
INNER JOIN ".TBL_USER_LEVEL." ON ".TBL_USERS.".userlevel = ".TBL_USER_LEVEL.".user_level_id
INNER JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".country OR ".TBL_USERS.".bcountry = ".TBL_COUNTRIES.".country_id
INNER JOIN ".TBL_STATES." ON ".TBL_USERS.".states OR ".TBL_USERS.".bstates = ".TBL_STATES.".states_id
WHERE ".TBL_USERS.".username = '$username'");
i changed the query to; and the error im gettin is
PHP Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 1066 Not unique table/alias: 'countries'' in
$sql = $this->connection->query("SELECT * FROM ".TBL_USERS."
INNER JOIN ".TBL_USER_LEVEL." ON ".TBL_USERS.".userlevel = ".TBL_USER_LEVEL.".user_level_id
INNER JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".country = ".TBL_COUNTRIES.".country_id
INNER JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".bcountry = ".TBL_COUNTRIES.".country_id
INNER JOIN ".TBL_STATES." ON ".TBL_USERS.".states = ".TBL_STATES.".states_id
INNER JOIN ".TBL_STATES." ON ".TBL_USERS.".bstates = ".TBL_STATES.".states_id
WHERE ".TBL_USERS.".username = '$username'");
OK here is correct syntax thanks a lot to #Tiberiu-Ionuț Stan
$sql = $this->connection->query("SELECT * FROM ".TBL_USERS."
LEFT JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".country = ".TBL_COUNTRIES.".country_id
LEFT JOIN ".TBL_COUNTRIES." AS ".TBL_COUNTRIES."_b ON ".TBL_USERS.".bcountry=".TBL_COUNTRIES."_b.country_id
INNER JOIN ".TBL_USER_LEVEL." ON ".TBL_USERS.".userlevel = ".TBL_USER_LEVEL.".user_level_id
LEFT JOIN ".TBL_STATES." ON ".TBL_USERS.".states = ".TBL_STATES.".states_id
LEFT JOIN ".TBL_STATES." AS ".TBL_STATES."_b ON ".TBL_USERS.".bstates=".TBL_STATES."_b.states_id
WHERE ".TBL_USERS.".username = '$username'");

Answer 1

You can use OR and AND inside join statements.
I do it all the time.
Here's one that works:
LEFT JOIN `currencies` ON (
`currency_foreign`=`invoice_entry_amount_currency`
AND
`currency_reference`='".$strTransformToCurrency."'
AND
`currency_date`=FLOOR(`invoice_paid_timestamp`/86400)*86400
)
Problem is here:
INNER JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".country = ".TBL_COUNTRIES.".country_id
INNER JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".bcountry = ".TBL_COUNTRIES.".country_id
MySQL can't decide on which relation to join the countries table (because MySQL thinks .country and .countryb can be different - so after join it doesn't know which columns will be returned or used for conditions and ordering).
Try it like this:
INNER JOIN ".TBL_COUNTRIES." ON ".TBL_USERS.".country = ".TBL_COUNTRIES.".country_id
INNER JOIN ".TBL_COUNTRIES." AS ".TBL_COUNTRIES."_b ON ".TBL_USERS.".bcountry=".TBL_COUNTRIES."_b.country_id
In case you have really big tables, do an EXPLAIN with the full final query including conditions and ordering to find out if MySQL is doing a table copy because of "TBL_USERS AS TBL_USERS_B".

Answer 2

You cannot use constructs like JOIN table ON field OR another_field = expression, unless referenced field is of boolean type.
You should use constructs that will return boolean result, in your case something like this:
$sql = $this->connection->query("SELECT * FROM $TBL_USERS
JOIN $TBL_USER_LEVEL ON $TBL_USERS.userlevel = $TBL_USER_LEVEL.user_level_id
JOIN $TBL_COUNTRIES ON $TBL_USERS.country = $TBL_COUNTRIES.country_id
OR $TBL_USERS.bcountry = $TBL_COUNTRIES.country_id
JOIN $TBL_STATES ON $TBL_USERS.states = $TBL_STATES.states_id
OR $TBL_USERS.bstates = $TBL_STATES.states_id
WHERE $TBL_USERS.username = '$username'");
I have also used the variable directly, otherwise lots of string concatenations looks messy.
And your query as is now is open for SQLi.