Generates SQL clauses to be appended to a main query.

Parameters

$typestringrequired

Type of meta. Possible values include but are not limited to 'post', 'comment', 'blog', 'term', and 'user'.

$primary_tablestringrequired

Database table where the object being filtered is stored (eg wp_users).

$primary_id_columnstringrequired

ID column for the filtered object in $primary_table.

$contextobjectoptional

The main query object that corresponds to the type, for example a WP_Query, WP_User_Query, or WP_Site_Query.

Default:null

Return

• join string
  SQL fragment to append to the main JOIN clause.
• where string
  SQL fragment to append to the main WHERE clause.

Source

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 ( str_contains( $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 string[] $sql               Array containing the query's JOIN and WHERE clauses.
	 * @param array    $queries           Array of meta queries.
	 * @param string   $type              Type of meta. Possible values include but are not limited
	 *                                    to 'post', 'comment', 'blog', 'term', and 'user'.
	 * @param string   $primary_table     Primary table.
	 * @param string   $primary_id_column Primary column ID.
	 * @param object   $context           The main query object that corresponds to the type, for
	 *                                    example a `WP_Query`, `WP_User_Query`, or `WP_Site_Query`.
	 */
	return apply_filters_ref_array( 'get_meta_sql', array( $sql, $this->queries, $type, $primary_table, $primary_id_column, $context ) );
}

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Hooks

apply_filters_ref_array( ‘get_meta_sql’, string[] $sql, array $queries, string $type, string $primary_table, string $primary_id_column, object $context )

Filters the meta query’s generated SQL.

Changelog