本文介绍了PHP/SQL:仅使用一个查询,如果两个表中都有数据,则从两个表中选择行;否则,仅从一个表中进行SELECT的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有两个评分/投票表.一个用于用户投票和统计,另一个用于外部投票. 外部投票表始终具有数据,因为它的DEAFULT = 0,但用户投票仅包含任何用户为该特定ID投票的数据.
I have two rating/votes tables. One for user votes and stats and another for external votes. The external votes table always have data because it has a DEAFULT = 0, but the users votes only contains data if any user have voted for that specific ID.
所以我做这样的事情:
$sql = 'SELECT ratings_stats.votes, ratings_stats.total_value, ratings_stats.view, ratings_stats.fav, ratings_stats.wish, ratings_external.votes, ratings_external.total_value FROM ratings_stats, ratings_external WHERE ratings_stats.imdbID = ? AND ratings_stats.imdbID = ratings_external.imdbID LIMIT 1';我想从两个表中选择数据(如果可用),或者如果没有,则仅形成第二个(外部选票)表.
I want to select data from both tables if available OR only form the second (external votes) table if not.
如何在不进行新查询的情况下做到这一点?
How to can I do it without making a new query?
推荐答案SELECT ratings_stats.votes, ratings_stats.total_value, ratings_stats.view, ratings_stats.fav, ratings_stats.wish, ratings_external.votes, ratings_external.total_value FROM ratings_external LEFT JOIN ratings_stats ON ratings_stats.imdbID = ratings_external.imdbID WHERE ratings_external.imdbID = ? LIMIT 1
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PHP/SQL:仅使用一个查询,如果两个表中都有数据,则从两个表中选择行;否则,仅从一个表中进行SELECT
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