WordPress’s query function allows you to execute any SQL query on the WordPress database. It is best used when there is a need for specific, custom, or otherwise complex SQL queries. For more basic queries, such as selecting information from a table, see the other wpdb functions above such as get_results, get_var, get_row or get_col.
Syntax
<?php $wpdb->query('query'); ?>
Read more from https://codex.wordpress.org/Class_Reference/wpdb#Running_General_Queries