maybe_add_column( string $table_name, string $column_name, string $create_ddl )

Source

File: wp-admin/includes/upgrade.php

function maybe_add_column( $table_name, $column_name, $create_ddl ) {
	global $wpdb;

	foreach ( $wpdb->get_col( "DESC $table_name", 0 ) as $column ) {
		if ( $column === $column_name ) {
			return true;
		}
	}

	// Didn't find it, so try to create it.
	$wpdb->query( $create_ddl );

	// We cannot directly tell that whether this succeeded!
	foreach ( $wpdb->get_col( "DESC $table_name", 0 ) as $column ) {
		if ( $column === $column_name ) {
			return true;
		}
	}

	return false;
}