在不動表結構的情況下還能優(yōu)化該SQL嗎（效率太低了）

SELECT DISTINCT
    GROUP_CONCAT(
        DISTINCT pch.erpContractNumber
    ) AS fbk22,
    poh.*, IFNULL(eei.shortName, eei.fullName) AS companyShortName,
    GROUP_CONCAT(DISTINCT poi.fbk7) AS materialNumber
FROM
    purchase_order_header poh
LEFT JOIN purchase_order_item poi ON poh.purchaseOrderNumber = poi.purchaseOrderNumber
AND poh.elsAccount = poi.elsAccount
LEFT JOIN els_enterprise_info eei ON eei.elsAccount = poh.toElsAccount
LEFT JOIN purchase_contract_head pch ON pch.elsAccount = poh.elsAccount
AND poh.purchaseOrderNumber = pch.erpContractNumber
AND pch.fbk15 = '1'
WHERE
    poh.elsAccount = '120000'
AND poh.orderStatus IN ("0","1","2","3","4","5","6","7")
AND poh.orderSendStatus IN ("0")
GROUP BY
    poh.purchaseOrderNumber
ORDER BY
    poh.logtime DESC,
    poh.purchaseOrderNumber DESC