Question

I have 2 tables one is for articles and second is for comments, now I want to get total number of comments and all articles details using 1 query, I dont want to use 2 queries one separately for article details and one for comments, can someone please help me get total number of comments on a specific article and all its comments..

article table… article_id
comments table…. comment_id, comment_article_id

normal to get comments I so
SELECT COUNT(*) as total ….

now I want to get both thing (full articles details from article_id) and from comments table total number of comments (and if possible all comments details on that article ID) with only one query…

regards

Answer 1

To get the article details and number of comments you can use the following

SELECT 
    articles.*,
    COALESCE(COUNT(comments.comment_id),0) AS numberOfCommments

FROM articles
LEFT JOIN comments
ON comments.comment_article_id = articles.article_id
AND comments.comment_type = 'B'

// If selecting a specific article use this line
WHERE articles.article_id = [[ARTICLE_ID]]

// If selecting all articles with counts use this line
GROUP BY articles.article_id

You can’t really get the comment details in the same query as the articles table due to the fact that the two will most likely have different fields. If you would really like to just get the article followed by all comments then something like the following would work. With the following, make sure that the columns in the first query match the columns in the second (i.e. the title column from the article matches either an empty string (shown) or a title column from the comments). I would personally not do this, and instead would just do 2 queries, one to get the article details and one to get any comments as that way it doesn’t matter that the column types may not match, and it also means the articles query doesn’t need joining onto comments as you can just count the number of rows that are in the comments query

Single query union method, not advised

(
    SELECT
        'article' AS rowType,
        article_date_posted,
        article_title,
        article_content
    FROM articles
    WHERE article_id = [[ARTICLE_ID]]
)
UNION
(
    SELECT
        'comment' AS rowType,
        comment_date_posted,
        '',  // Empty string because comments usually have no title
        comment_content
    FROM comments
    WHERE comment_article_id = [[ARTICLE_ID]]
    AND comment_type = 'B'
    ORDER BY comment_date_posted ASC
)

2-query method, simpler and in most cases more efficient

//articles query
SELECT *
FROM articles
WHERE article_id = [[ARTICLE_ID]];

//comments query
SELECT *
FROM comments
WHERE comment_article_id = [[ARTICLE_ID]]
AND comment_type = 'B';