为什么输出数据与Union All查询中的列不对应

Question

这是一段输出

array（7）{[“type”] =＆gt; string（16）“new post comment”[“book_id”] =＆gt; string（1）“1”[“name”] =＆gt; string（9）“whatever”[“author_id”] =＆gt; string（4）“test”[“content”] =＆gt; string（19）“2011-07-16 03:20:01”[“create_time”] =＆gt; string（1）“3”[“id”] =＆gt; string（1）“1”}

这是我的查询的一部分

                     SELECT 'bookcomment' AS type
                                ,b.book_id
                                ,b.name 
                                ,c.book_id 
                                ,c.author_id 
                                ,c.content
                                ,c.create_time AS create_time
                                ,u.id 
                                ,u.name 
                                FROM tbl_book AS b,
                                            tbl_book_comment AS c,
                                            tbl_user AS u
                                WHERE u.id=c.author_id in (1,2) AND b.book_id=c.book_id


                    UNION ALL

                    SELECT 'new post comment' AS type
                            ,po.post_id 
                            ,po.title
                            ,pc.author_id
                            ,pc.content
                            ,pc.create_time AS create_time
                            ,pc.post_id
                            ,u.id
                            ,u.name
                            FROM tbl_post as po,
                                        tbl_post_comment as pc,
                                        tbl_user as u
                            WHERE u.id=pc.author_id in(1,2) AND po.post_id=pc.post_id


                    UNION ALL

                    SELECT 'bookrating' AS type
                                ,b.book_id as one
                                ,b.name
                                ,ra.book_id
                                ,ra.user_id
                                ,ra.rating
                                ,ra.create_time AS create_time
                                ,u.id
                                ,u.name
                                FROM tbl_book AS b,
                                            tbl_user_book_rating AS ra,
                                            tbl_user AS u
                                WHERE u.id=ra.user_id in (1,2) AND b.book_id=ra.book_id


                    UNION ALL...
ORDER BY create_time DESC

如图所示，对应于'author_id'的数据应该对应'content'，'content'应该是'create_time'。我的查询出了什么问题？

Answer 1

看起来你已经混淆了第二个SELECT中列的顺序。你的列是这样的（左边是第一个查询，中间是第二个，右边是第三个）：

type            type            type
b.book_id       po.post_id      one
b.name          po.title        b.name
c.book_id       pc.author_id    ra.book_id
c.author_id     pc.content      ra.user_id
c.content       create_time     ra.rating
create_time     pc.post_id      create_time
u.id            u.id            u.id
u.name          u.name          u.name

订单在pc.author_id看起来混淆了。