Alternative method to delete child element from parent besides on delete cascade - php

Question

I have 2 tables:
Warehouse (Parent)
Subwarehouse (Child)
Here is the creation of tables
//Create Warehouse Table
function einv_createWarehouseTable($conn, $db_type){
// Create SQL Statement To Create Table according to Database
$sql = "
CREATE TABLE IF NOT EXISTS `einv_warehouse` (
`einv_wh_id` INT(11) NOT NULL AUTO_INCREMENT,
`einv_wh_code` VARCHAR(4) NOT NULL,
`einv_wh_name` VARCHAR(255) NOT NULL,
`einv_wh_desc` TEXT NOT NULL,
`einv_wh_remark` TEXT NULL,
PRIMARY KEY (`einv_wh_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
";
//Create Sub Warehouse Table
function einv_createSubWarehouseTable($conn, $db_type){
// Create SQL Statement To Create Table according to Database
$sql = "
CREATE TABLE IF NOT EXISTS `einv_subwarehouse` (
`einv_whs_id` INT(11) NOT NULL AUTO_INCREMENT,
`einv_whs_wh_id` INT(11) NOT NULL,
`einv_whs_code` VARCHAR(4) NOT NULL,
`einv_whs_name` VARCHAR(255) NOT NULL,
`einv_whs_desc` TEXT NOT NULL,
`einv_whs_remark` TEXT NULL,
PRIMARY KEY (`einv_whs_id`),
FOREIGN KEY (`einv_whs_wh_id`) REFERENCES einv_warehouse(`einv_wh_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
";
I would like to be able to delete my parent table alongside clearing the entire child data.
I'd prefer an alternative method besides using on delete cascade which will result me into altering the table.
It is troublesome because these codings would require a drop and install process which is time consuming since there are many existing tables.
tl;dr - another method to delete all child data when selected parent id is
deleted
besides using on delete cascade
Here is my delete sql in my function.php page:
base_executeSQL("DELETE FROM einv_warehouse WHERE einv_wh_id = " . $whid . "");
base_executeSQL("DELETE FROM einv_subwarehouse WHERE einv_whs_id = " . $whid . "");