The function get_invoice_range() in the invoice report reporting/rep107.php uses the sql:
SELECT trans.trans_no, trans.reference
FROM 1_debtor_trans trans 
LEFT JOIN 1_voided voided ON trans.type=voided.type AND trans.trans_no=voided.id
WHERE trans.type=10 AND ISNULL(voided.id);
which extracts the invoices to be printed and example of it is:
trans_no    reference
1    001/2017
2    002/2017
3    003/2017
4    004/2017
The function get_customer_trans in sales/includes/db/cust_trans_db.inc uses the sql:
SELECT trans.*, ov_amount+ov_gst+ov_freight+ov_freight_tax+ov_discount AS Total,
    cust.name AS DebtorName, cust.address, 
    cust.curr_code, 
    cust.tax_id,
    trans.prep_amount>0 AS prepaid,
    com.memo_, 
    1_shippers.shipper_name, 
    1_sales_types.sales_type, 
    1_sales_types.tax_included, 
    branch.*, 
    cust.discount, 
    1_tax_groups.name AS tax_group_name, 
    1_tax_groups.id AS tax_group_id 
FROM 1_debtor_trans trans
    LEFT JOIN 1_comments com ON trans.type=com.type AND trans.trans_no=com.id
    LEFT JOIN 1_shippers ON 1_shippers.shipper_id=trans.ship_via, 
    1_debtors_master cust, 
    1_sales_types, 
    1_cust_branch branch, 
    1_tax_groups 
WHERE trans.debtor_no=cust.debtor_no
  AND 1_sales_types.id = trans.tpe
  AND branch.branch_code = trans.branch_code
  AND branch.tax_group_id = 1_tax_groups.id;
The delivery date is in another record (type=13) and not in the invoice record (type=10).