有人可以向我解释这个SQL查询吗？

Question

我正在阅读这篇文章,我正在尝试理解这个SQL语句,但我仍然对SQL有些新意.

我不确定评论和c是什么意思.
我认为其中一个是表名,但我不确定另一个.此外,显然其中有一个子查询,我没有任何经验:

  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

第一个列表是所有需要选择的字段，其前缀c是后面表格的别名comment。

查询中的查询是子查询，它运行执行类似操作并.clineage与%（通配符）连接的查询。该子查询结果保存在replies.

结果按 排序linea。