Můžete zkusit tuto verzi (v podstatě dostane nejprve 420 řádků corder
tabulky, ponechá si 20 z nich a poté provede 3 vnější spojení):
SELECT
corder.id,
corder.public_id,
CONCAT(buyer.fname," ",buyer.lname) AS buyer_name,
corder.status,
corder.payment,
corder.reserved AS R,
corder.tracking_id != "" AS A,
corder.payment_received AS pay_date,
invoice.invoice_no AS inv,
invoice.receipt_no AS rec,
invoice.public AS pub_inv,
proforma.proforma_no AS prof,
proforma.public AS pub_pf,
corder.rating,
corder.rating_comments!="" AS got_comment
FROM
( SELECT *
FROM corder
ORDER BY
id DESC
LIMIT 400, 20
)
AS corder
LEFT JOIN user as buyer ON buyer.id = corder.buyer
LEFT JOIN invoice AS invoice ON invoice.id = corder.invoice
LEFT JOIN invoice AS proforma ON proforma.id = corder.proforma
ORDER BY
corder.id DESC ;