WP_Meta_Query::get_sql( string $type, string $primary_table, string $primary_id_column, object $context = null )

Source

File: wp-includes/class-wp-meta-query.php

public function get_sql( $type, $primary_table, $primary_id_column, $context = null ) {
		$meta_table = _get_meta_table( $type );
		if ( ! $meta_table ) {
			return false;
		}

		$this->table_aliases = array();

		$this->meta_table     = $meta_table;
		$this->meta_id_column = sanitize_key( $type . '_id' );

		$this->primary_table     = $primary_table;
		$this->primary_id_column = $primary_id_column;

		$sql = $this->get_sql_clauses();

		/*
		 * If any JOINs are LEFT JOINs (as in the case of NOT EXISTS), then all JOINs should
		 * be LEFT. Otherwise posts with no metadata will be excluded from results.
		 */
		if ( false !== strpos( $sql['join'], 'LEFT JOIN' ) ) {
			$sql['join'] = str_replace( 'INNER JOIN', 'LEFT JOIN', $sql['join'] );
		}

		/**
		 * Filters the meta query's generated SQL.
		 *
		 * @since 3.1.0
		 *
		 * @param array  $sql               Array containing the query's JOIN and WHERE clauses.
		 * @param array  $queries           Array of meta queries.
		 * @param string $type              Type of meta.
		 * @param string $primary_table     Primary table.
		 * @param string $primary_id_column Primary column ID.
		 * @param object $context           The main query object.
		 */
		return apply_filters_ref_array( 'get_meta_sql', array( $sql, $this->queries, $type, $primary_table, $primary_id_column, $context ) );
	}