Here is a good example for the chapter where you need to use “INNER JOIN” to join two sql tables.
Create two tables for your database.
Table 1: “countries”, with 2 elements: id_country (auto increment), country.
Table 2: “states”, with 3 elements: id_state (auto increment), id_country, state.
So we could join the tables in our SQL query so if we want to display an element from “states”, it will be without having to match the “id_country” values with two requests, just with 1.
Example:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | <? require_once('engine.php'); ?> <? $requestSQL = "SELECT * FROM countries INNER JOIN states ON countries.id_country = states.id_country"; // we first select as normal, our countries table, then use INNER JOIN and declare the second table, "states", use "ON", then match the table elements using a prefix with the table names. $query = mysqli_query($dbc, $requestSQL); while ($row = mysqli_fetch_array($query)) { $country = $row['country']; $state = $row['state']; echo ''.$state.''; } ?> |
When echo-ing “state”, it will really echo the state.
You can see more regarding INNER JOIN here: http://www.w3schools.com/sql/sql_join_inner.asp