以下方法测测 SELECT a.* ,CONCAT(ifnull(c.单位名称,''),' ',ifnull(c.秒送,'')) AS 主送 FROM 表一 AS a LEFT JOIN 表三 AS b ON b.序号=a.主送 LEFT JOIN (SELECT c1.序号,group_concat(c2.单位名称) AS 秒送 FROM 表二 AS c1 INNER JOIN 表三 AS c2 ON c1.抄送=c2.序号 GROUP BY c1.序号) AS c ON a.关联号=c.序号
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或用concat_ws处理null情况 SELECT a.* ,concat_ws(' ',c.单位名称,c.秒送) AS 主送 FROM 表一 AS a LEFT JOIN 表三 AS b ON b.序号=a.主送 LEFT JOIN (SELECT c1.序号,group_concat(c2.单位名称) AS 秒送 FROM 表二 AS c1 INNER JOIN 表三 AS c2 ON c1.抄送=c2.序号 GROUP BY c1.序号) AS c ON a.关联号=c.序号
SELECT
a.*
,CONCAT(ifnull(c.单位名称,''),' ',ifnull(c.秒送,'')) AS 主送
FROM 表一 AS a
LEFT JOIN 表三 AS b ON b.序号=a.主送
LEFT JOIN (SELECT c1.序号,group_concat(c2.单位名称) AS 秒送 FROM 表二 AS c1 INNER JOIN 表三 AS c2 ON c1.抄送=c2.序号 GROUP BY c1.序号) AS c ON a.关联号=c.序号
SELECT
a.*
,concat_ws(' ',c.单位名称,c.秒送) AS 主送
FROM 表一 AS a
LEFT JOIN 表三 AS b ON b.序号=a.主送
LEFT JOIN (SELECT c1.序号,group_concat(c2.单位名称) AS 秒送 FROM 表二 AS c1 INNER JOIN 表三 AS c2 ON c1.抄送=c2.序号 GROUP BY c1.序号) AS c ON a.关联号=c.序号
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