此SQL连接查询出了什么问题

Question

因此，所有字段和表都存在并且具有相关数据（已选中）。 但这并没有给我任何结果。

SELECT `r`.*, `k`.`keyword`, `c`.`name`, `c`.`state`
FROM `local_rank` as `r`
LEFT JOIN `keyword` as `k` ON `r`.`keyword_id` = `k`.`keyword_id`
LEFT JOIN `campaign` as `c` ON `k`.`campaign_id` = `c`.`campaign_id`
WHERE `c`.`campaign_id` = '6'
AND `r`.`location` = '60602'
ORDER BY `local_rank_id` DESC
 LIMIT 6, 60602

当我删除任何一个WHERE / AND条件时，它将获取数据行。

Answer 1

由于您使用带偏移量的“ LIMIT”，因此至少应显示60602条以上的记录。 您可以通过删除LIMIT偏移量并计算返回的行数来验证这一点。

SELECT `r`.*, `k`.`keyword`, `c`.`name`, `c`.`state`
FROM `local_rank` as `r`
LEFT JOIN `keyword` as `k` ON `r`.`keyword_id` = `k`.`keyword_id`
LEFT JOIN `campaign` as `c` ON `k`.`campaign_id` = `c`.`campaign_id`
WHERE `c`.`campaign_id` = '6'
AND `r`.`location` = '60602'
ORDER BY `local_rank_id` DESC
 LIMIT 6

Answer 2

从限制中删除偏移量，您可能没有超过60602行与您的查询匹配

SELECT `r`.*, `k`.`keyword`, `c`.`name`, `c`.`state`
FROM `local_rank` as `r`
LEFT JOIN `keyword` as `k` ON `r`.`keyword_id` = `k`.`keyword_id`
LEFT JOIN `campaign` as `c` ON `k`.`campaign_id` = `c`.`campaign_id`
WHERE `c`.`campaign_id` = '6'
  AND `r`.`location` = '60602'
ORDER BY `local_rank_id` DESC
LIMIT 6