Here is my example code if anyone can please explain just tell me the syntax of MySQL ...
SELECT s.sales_id,s.pid,s.quantity,IFNULL((SELECT i.invoice_id FROM
invoice AS i WHERE i.checkin_id NOT IN (SELECT crt.checkin_id FROM
checkin_request_ticket as crt WHERE crt.salvage_part='1') AND
i.invoice_id=s.sales_id),s.quantity) as checkquan
FROM sales as s
The following recommendations will help you in your SQL tuning process.
You'll find 3 sections below:
ALTER TABLE `checkin_request_ticket` ADD INDEX `checkin_ticket_idx_salvage_part_checkin_id` (`salvage_part`,`checkin_id`);
ALTER TABLE `invoice` ADD INDEX `invoice_idx_invoice_id` (`invoice_id`);
SELECT
s.sales_id,
s.pid,
s.quantity,
IFNULL((SELECT
i.invoice_id
FROM
invoice AS i
WHERE
NOT EXISTS (SELECT
1
FROM
checkin_request_ticket AS crt
WHERE
(crt.salvage_part = '1')
AND (i.checkin_id = crt.checkin_id))
AND i.invoice_id = s.sales_id), s.quantity) AS checkquan
FROM
sales AS s