Номер ошибки: 1241 Операнд должен содержать 1 колонку (ы)

Question

SELECT * 
    FROM `tbl_equipments` as `E` 
    JOIN `tbl_equipment_category` as `C` ON `C`.`equipment_category_id`=`E`.`equipment_category_id` 
    JOIN `tbl_suppliers` as `S` ON `S`.`supplier_id`=`E`.`supplier_id` 
    JOIN `tbl_site_users` as `U` ON `U`.`user_id`=`E`.`created_by` 
    JOIN `tbl_currency` as `R` ON `R`.`currency_id`=`E`.`equipment_currency_id` 
    WHERE `E`.`site_id` = '3' 
    AND (SELECT * 
     FROM `tbl_user_delegates` as `D` 
     LEFT JOIN `tbl_equipments` as `E` ON `E`.`approve_by`=`D`.`delegate_from_user` 
     WHERE `D`.`delegate_from_date` <= '2016-10-27' 
     AND `D`.`delegate_to_date` >= '2016-10-27' AND `D`.`delegate_to_user` = '5' 
     ORDER BY `E`.`equipment_id` DESC) 
    AND (`E`.`approve_flg` =0 and `E`.`rejection_flg` =0) AND `E`.`approve_by` = '5' 

Answer 1

ваших, и (подзапрос) возврат * это неправильно

вы должны использовать существует

SELECT * 
    FROM `tbl_equipments` as `E` 
    JOIN `tbl_equipment_category` as `C` ON `C`.`equipment_category_id`=`E`.`equipment_category_id` 
    JOIN `tbl_suppliers` as `S` ON `S`.`supplier_id`=`E`.`supplier_id` 
    JOIN `tbl_site_users` as `U` ON `U`.`user_id`=`E`.`created_by` 
    JOIN `tbl_currency` as `R` ON `R`.`currency_id`=`E`.`equipment_currency_id` 
    WHERE `E`.`site_id` = '3' 
    AND EXISTS (SELECT * 
     FROM `tbl_user_delegates` as `D` 
     LEFT JOIN `tbl_equipments` as `E` ON `E`.`approve_by`=`D`.`delegate_from_user` 
     WHERE `D`.`delegate_from_date` <= '2016-10-27' 
     AND `D`.`delegate_to_date` >= '2016-10-27' AND `D`.`delegate_to_user` = '5' 
     ORDER BY `E`.`equipment_id` DESC) 
    AND (`E`.`approve_flg` =0 and `E`.`rejection_flg` =0) AND `E`.`approve_by` = '5' 

ADN Буквально советы заказать по в выберите select is unuseful