Question

这是我的查询

SELECT `t`.`id` AS `t0_c0`
 , `news`.`id` AS `t2_c0`
 , `news`.`title` AS `t2_c1`
 , `news`.`url` AS `t2_c2`
 , `news`.`date` AS `t2_c3`
 , `news`.`hash` AS `t2_c4`
 , `news`.`list_id` AS `t2_c5`
FROM
`words` `t`
LEFT OUTER JOIN `words_news` `news_news`
ON (`t`.`id` = `news_news`.`word_id`)
LEFT OUTER JOIN `news` `news`
ON (`news`.`id` = `news_news`.`news_id`)
WHERE
  (`t`.`id` IN (8229, 8574, 7901))

我只需从news表中选择5条新闻，但不知道如何编写查询？

Answer 1

试试这个：

    SELECT `t`.`id` AS `t0_c0`
     , `news`.`id` AS `t2_c0`
     , `news`.`title` AS `t2_c1`
     , `news`.`url` AS `t2_c2`
     , `news`.`date` AS `t2_c3`
     , `news`.`hash` AS `t2_c4`
     , `news`.`list_id` AS `t2_c5`
FROM
  `words` `t`
LEFT OUTER JOIN `words_news` `news_news`
ON (`t`.`id` = `news_news`.`word_id`)
LEFT OUTER JOIN (SELECT * FROM `news` LIMIT 5) `news`
ON (`news`.`id` = `news_news`.`news_id`)
WHERE
  (`t`.`id` IN (8229, 8574, 7901));

或

SELECT `t`.`id` AS `t0_c0`
 , `news`.`id` AS `t2_c0`
 , `news`.`title` AS `t2_c1`
 , `news`.`url` AS `t2_c2`
 , `news`.`date` AS `t2_c3`
 , `news`.`hash` AS `t2_c4`
 , `news`.`list_id` AS `t2_c5`
FROM
  `words` `t`
LEFT OUTER JOIN `words_news` `news_news`
ON (`t`.`id` = `news_news`.`word_id`)
LEFT OUTER JOIN `news` `news`
ON (`news`.`id` = `news_news`.`news_id`)
JOIN (SELECT @var_ctr := 0) a
WHERE IF(`news`.`id` IS NOT NULL, @var_ctr := @var_ctr + 1, @var_ctr) <= 5
      AND (`t`.`id` IN (8229, 8574, 7901));

Mysql LEFT OUTER JOIN与LIMIT？

1 个答案: