有人可以向我解释这个SQL查询吗？

Question

I'm reading this article and I'm trying to understand this SQL statement but I am still somewhat new to SQL.

I'm not sure what comment and c refer to.
I think one of them is the table name but I am not sure of the other. Also, apparently there is a subquery within it which I have not had any experience with:

  SELECT c.id, c.user_id, c.body, c.deep, c.lineage, c.parent_id,
         (SELECT COUNT(*) 
            FROM comment 
           WHERE comment.lineage LIKE (CONCAT(c.lineage,'%')) 
             AND comment.lineage != c.lineage) AS replies
    FROM comment as c
ORDER BY c.lineage

Answer 1

SELECT c.id,
       c.user_id,
       c.body, 
       c.deep, 
       c.lineage, 
       c.parent_id, (
       SELECT COUNT(*)
         FROM comment
        where comment.lineage LIKE (CONCAT(c.lineage,'%'))
          AND comment.lineage!=c.lineage)
       as replies
       FROM comment as c 
       order by c.linea

The first list are all the fields to be selected, with the prefix of c which is the alias later to the comment table.

The query in a query is a subquery, which runs that query which does a like and concatenates .clineage with % (which is the wildcard). This subquery result is saved in replies.

The results are ordered by linea.