我正在尝试对多个表进行左连接。但是,它显示了所有左连接表结果。主表将是 'a' 但它显示重复的 id 因为它的 id 在其他表上存在多次。如何只选择其他表的第一行?或选择表 'a' 上的不同结果?这是我的 SQL
SELECT a.adsId, a.adsName, a.adsUrl, a.sourceFileName, c.userName, d.preferenceId, e.ppv FROM y5ads_new.ads_source a
INNER JOIN y5ads_new.campaign b ON a.campaignId=b.campaignId
INNER JOIN y5ads_new.system_member c ON b.createdBy=c.memberId
INNER JOIN y5ads_new.ads_preference d ON a.adsId=d.adsId
INNER JOIN y5ads_new.ads_rates e ON a.adsId=e.adsId
WHERE a.status='2' AND a.deleted='False' AND CURDATE() BETWEEN a.startDate and a.endDate
AND b.status='2' AND b.deleted='False' AND CURDATE() BETWEEN b.startDate and b.endDate
AND d.deleted='False' AND CURDATE() BETWEEN d.startDate and d.endDate
AND e.is_active='1' AND CURDATE() BETWEEN e.startDate and e.endDate
ORDER BY a.adsId DESC, d.preferenceId DESC, e.id DESC
最佳答案
使您的 ID 不同并使用 LEFT JOIN:
SELECT a.adsId, a.adsName, a.adsUrl, a.sourceFileName, c.userName, d.preferenceId, e.ppv
FROM y5ads_new.ads_source AS a
LEFT JOIN (SELECT DISTINCT campaignId as campaignId FROM y5ads_new.campaign) AS b
ON a.campaignId=b.campaignId
LEFT JOIN (SELECT DISTINCT memberId AS memberId, userName FROM y5ads_new.system_member) AS c
ON b.createdBy=c.memberId
LEFT JOIN (SELECT DISTINCT adsId AS adsId, preferenceId FROM y5ads_new.ads_preference) AS d
ON a.adsId=d.adsId
LEFT JOIN (SELECT DISTINCT adsId AS adsId, ppv FROM y5ads_new.ads_rates) AS e
ON a.adsId=e.adsId
WHERE ...
关于MYSQL:左连接仅第一行或选择不同,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26055926/