MySQL查询问题: Can't select columns from another table

Question

我的 SQL 语句看起来像这样

SELECT SQL_CALC_FOUND_ROWS q.id, q.question, sb.subject, c.chapter, sc.section, p.paragraph 
FROM questions AS q
     , subjects AS sb
     , sections AS sc
     , chapters AS c
     , paragraphs AS p 
WHERE (sb.id=q.subject AND c.id=q.chapter AND sc.id=q.section AND p.id=q.paragraph) AND (q.author_id=1) 
ORDER BY  q.id asc 
LIMIT 0, 25

如您所见，这些表通过 id 相互关联。问题是，我得到的是 questions 表的 subject 列，而不是 subjects 表的 subject 列。我在这里缺少什么？

注意

我提供了主题作为示例。实际上，所有三个部分 AS sc、章节 AS c、段落 AS p 都不起作用。我只得到主题。

Answer 1

显然，您问题中的查询很好，但仍要使用此语句来挖掘它，并查看 subjects_subject 列中出现的内容:

SELECT SQL_CALC_FOUND_ROWS q.id, q.question, sb.subject as subjects_subject, c.chapter, sc.section, p.paragraph 
FROM questions AS q
     , subjects AS sb
     , sections AS sc
     , chapters AS c
     , paragraphs AS p 
WHERE (sb.id=q.subject AND c.id=q.chapter AND sc.id=q.section AND p.id=q.paragraph) AND (q.author_id=1) 
ORDER BY  q.id asc 
LIMIT 0, 25