Question

我正在尝试查询多个WordPress表，我一直在学习。

这是我到目前为止所拥有的

SELECT 
   tr.object_id, 
   tr.term_taxonomy_id, 
   p.ID, 
   p.post_date, 
   p.post_title, 
   p.post_excerpt, 
   p.guid, 
   t.term_id, 
   t.name, 
   tt.taxonomy
FROM 
   wp_116_term_relationships AS tr, 
   wp_116_posts AS p, 
   wp_116_terms AS t LEFT JOIN 
   wp_116_term_taxonomy as tt ON tt.term_id = t.term_id
WHERE 
   p.post_type = 'post'
   AND p.ID = tr.object_ID
   AND tr.term_taxonomy_id = tt.term_taxonomy_id
   AND p.post_date > '2013-06-01'

这是我得到的（对不起，我无法弄清楚如何发布这个清洁工 - 希望它有意义）

object_id term_taxonomy_id ID post_date post_title post_excerpt guid term_id name  taxonomy 
2356     33      2356    2013-06-07 15:56:54     Test Post for Reports       http://domain.com/?p=2356   7496    Marketing Updates   category
2356     32      2356    2013-06-07 15:56:54     Test Post for Reports       http://domain.com/?p=2356   470     News Updates    category 
2356     70      2356    2013-06-07 15:56:54     Test Post for Reports       http://domain.com/?p=2356   46408   Tag Test 1      post_tag 
2356     72      2356    2013-06-07 15:56:54     Test Post for Reports       http://domain.com/?p=2356   46410   Tag Test 2      post_tag 
2356     74      2356    2013-06-07 15:56:54     Test Post for Reports       http://domain.com/?p=2356   46412   Tag Test 3      post_t

如何将数据与名称字段分开，以便如果它是post_tag，则它位于一列（post_tag）中，如果它是一个类别，则它位于另一列（类别）中？例如：

object_id term_taxonomy_id ID post_date post_title post_excerpt guid term_id post_tag category
2356     33      2356    2013-06-07 15:56:54     Test Post for Reports       http://domain.com/?p=2356   7496    Marketing Updates   Tag Test 1

Answer 1

使用CASE声明应该相当直接

   SELECT 
    tr.object_id, 
    tr.term_taxonomy_id, 
    p.ID, 
    p.post_date, 
    p.post_title, 
    p.post_excerpt, 
    p.guid, 
    t.term_id, 
    CASE WHEN tt.taxonomy = 'category' THEN t.name ELSE NULL END AS category_name,
    CASE WHEN tt.taxonomy = 'post_tag' THEN t.name ELSE NULL END AS post_tag_name
    FROM 
    wp_116_term_relationships AS tr, 
    wp_116_posts AS p, 
    wp_116_terms AS t
    LEFT JOIN wp_116_term_taxonomy as tt ON tt.term_id = t.term_id
    WHERE 
    p.post_type = 'post'
    AND p.ID = tr.object_ID
    AND tr.term_taxonomy_id = tt.term_taxonomy_id
    AND p.post_date > '2013-06-01'

MySQL查询基于其他表创建列

1 个答案: