我可以對父查詢中的嵌入式查詢的結果進行數學運算嗎？

Question

考慮查詢：

SELECT n.nid, 
    (select count(*) as count from view_log where id = n.nid) AS the_count, 
    (the_count + 1) as the_bumped_count 
    FROM node n 

當我跑，我得到Unknown column 'the_count' in 'field list'。有沒有辦法解決？看來the_count應該在查詢中可見並可用，但顯然不是。順便說一句，我也試過SUM(the_count, 1)，但那也失敗了。謝謝！

Answer 1

，我認爲這會工作，以及，只需要你算一次：

SELECT nid, the_count, the_count+1 as the_bumped_count 
FROM (
    SELECT n.nid, 
     COUNT(v.*) the_count, 
    FROM node n 
     LEFT JOIN view_log v on n.nid = v.id 
    GROUP BY n.nid 
) t 

還是要回到你的語法：

SELECT nid, the_count, the_count+1 as the_bumped_count 
FROM (
    SELECT n.nid, 
     (select count(*) as count from view_log where id = n.nid) AS the_count 
    FROM node n 
) t 

祝你好運。

Answer 2

您不能使用在您想對其進行計算的同一級別上定義的ALIAS。

SELECT n.nid, 
    (select count(*) as count from view_log where id = n.nid) AS the_count, 
    ((select count(*) as count from view_log where id = n.nid) + 1) as the_bumped_count 
    FROM node n 

或更好地使用子查詢，

SELECT nid, 
     the_count, 
     the_count + 1 AS the_bumped_count 
FROM 
( 
    SELECT n.nid, 
      (select count(*) as count from view_log where id = n.nid) AS the_count 
    FROM node n 
) s