表：
经销商 dealer 字段 uid parent_uid name
联系人 contact 字段 uid dealer_id contact_main
需求：
想要查询到经销商的信息，和本经销商的主要联系人的信息 ，和本经销商的父级经销商的name
情况：
可能有parent_id是null
sql语句：
SELECT dea.uid uid, dea.enabled_flag enabledFlag, dea.delete_flag deleteFlag, dea.tenement_id tenementId, dea.parent_id parentId, pd.name parentName, dea.name name, dea.type type, dea.bar_code barCode, dea.outer_code outerCode, dea.outer_id outerId, dea.mne_code mneCode, dea.address address, dea.address_xy addressXy, dea.business_area businessArea, dea.business_area_xy businessAreaXy, con.name contactName, con.mobile mobile FROM dealer AS dea LEFT JOIN (select * from contact where tenement_id = ‘9f63f84f-52c6-4c8e-b3c3-66b9f1f283ba‘ and main_contact = 1) con ON dea.uid = con.dealer_id LEFT JOIN dealer pd on pd.uid = dea.parent_id
原文：https://www.cnblogs.com/sxdcgaq8080/p/9205462.html