sql查詢默認值和null做關聯

遇到sql查詢，如果有值就顯示，如果是空則顯示默認值，關聯表，關聯字段出現null，解決方法加ifnull

例子：

SELECT
    fici.id,
    fici.vin,
    fici.car_series AS carSeries,
    fici.car_model AS carModel,
    fici.open_status AS openStatus,
    fici.apply_time AS applyTime,
    IFNULL(
        ficmp.min_pic_url,
        ficmp1.min_pic_url
    ) AS picUrl,
    IFNULL(
        ficmp.model_describe,
        ficmp1.model_describe
    ) AS modelDescribe,
    fici.gbook_activate_time AS gbookActivateTime,
    IFNULL(
        ficmp.series_name,
        ficmp1.series_name
    ) AS seriesName
FROM
    ftms_iov_car_info fici
LEFT JOIN ftms_iov_enterprise_user fie ON fici.enterprise_subcode = fie.enterprise_account
LEFT JOIN (
    SELECT
        ficm.model_name,
        fi.pic_url,
        fi.pic_color,
        fi.min_pic_url,
        ficm.model_describe,
        fics.series_name
    FROM
        ftms_iov_car_model AS ficm
    LEFT JOIN ftms_iov_car_model_pic AS fi ON fi.car_model_id = ficm.id
    LEFT JOIN ftms_iov_car_series AS fics ON ficm.series_id = fics.id
    AND fi.del_flag = 0
    AND ficm.del_flag = 0
    AND fi.default_flag = 0
    AND fics.del_flag = 0
) ficmp ON fici.car_series = ficmp.model_name
AND fici.car_color = ficmp.pic_color
LEFT JOIN (
    SELECT
        ficm1.model_name,
        fi1.pic_url,
        fi1.pic_color,
        fi1.min_pic_url,
        ficm1.model_describe,
        fics1.series_name
    FROM
        ftms_iov_car_model AS ficm1
    LEFT JOIN ftms_iov_car_model_pic AS fi1 ON fi1.car_model_id = ficm1.id
    LEFT JOIN ftms_iov_car_series AS fics1 ON ficm1.series_id = fics1.id
    AND fi1.del_flag = 0
    AND ficm1.del_flag = 0
    AND fi1.default_flag = 1
    AND fics1.del_flag = 0
) ficmp1 ON fici.car_series = ficmp1.model_name
AND ifnull(fici.car_color, '') = ifnull(ficmp1.pic_color, '')
WHERE
    fici.enterprise_code = '**********'
AND fici.car_type = 2
AND fici.del_flag = 0
AND fici.open_status IN (2)
ORDER BY
    fici.create_time DESC