Question

我有两张桌子：

这是我的posts表：

+-----+----------------+-------------+
| ID  |   post_title   | post_status |
+-----+----------------+-------------+
| 105 | Red Shirt      | active      |
| 106 | Green Shoes    | active      |
| 107 | Blue Hat       | hidden      |
+-----+----------------+-------------+

这是我的meta表：

+-----------+------+
| object_id | lang |
+-----------+------+
|       105 | en   |
|       106 | fr   |
|       107 | en   |
+-----------+------+

我正在尝试编写一个SQL查询，该查询返回posts post_status active和lang en的所有105的ID。使用这两个表，应该只有一个结果（ID）。

我无法将object_id与var switchTab = function() { var p = $(this).parent('li'); var i = p.index(); var s = section.eq(i); var c = s.find('*'); section.removeClass('active'); sectionContent.removeAttr('style'); s.addClass('active'); c.css({ transform: 'none', opacity: 1 }); linkParent.removeClass('active'); p.addClass('active'); return false; }; link.on('click', switchTab); </script>匹配。非常感谢任何帮助，谢谢。

Answer 1

SELECT p.ID
FROM posts p, meta m
WHERE p.ID = m.object_id
AND p.post_status = 'active'
AND m.lang='en'

Answer 2

加入两个表，然后指定条件：

SELECT posts.ID
FROM posts
INNER JOIN meta ON meta.object_id = posts.id
WHERE posts.post_status = 'active'
  AND meta.lang = 'en'

Answer 3

鉴于您只想要那些在两个表中都有记录的行，您需要一个INNER JOIN。这里有关于不同联接类型的好帖子：SQL JOIN and different types of JOINs

对于您的查询，您需要以下内容：

SELECT
    PostTbl.ID -- The column(s) you want to select
FROM
    `posts` AS PostTbl -- I prefer aliasing every table so I keep the habit when self joining
INNER JOIN -- Since we want only the rows with records in both tables
    `meta` AS MetaTbl
    ON PostTbl.ID = MetaTbl.object_id -- The conditions on which we want the tables to join
WHERE
    PostTbl.post_status = 'active' -- Post is 'active'
    AND MetaTbl.lang = 'en'; -- Language is 'en'

如何编写这个基本的内连接SQL查询

3 个答案: