MySQL 到 PostgreSQL 查询别名 GROUP BY

Question

我有一个看起来像这样的表格

id   |   number
---------------
1       56721
2       56722
3       43981
4       43982
5       43983 
6       43984

My MySQL query looks like this:

SELECT CASE substr(number,1,2) WHEN '56' then 'class1' WHEN '43' then 'class2' else 'other' END as class, 
       CASE substr(number,3,2) WHEN '72' then 'subclass1', WHEN '98' then 'subclass2' ELSE 'other' END as subclass, count(id) as ct 
FROM table GROUP BY class, subclass HAVING class!='other' AND subclass!='other' 
ORDER BY class ASC, subclass DESC;

对应的 PostgreSQL 查询是什么？

Answer 1

为了使其更清晰，请将其包装在子查询上:

SELECT  class, subclass
FROM
    (
        SELECT  CASE substr(number,1,2) WHEN '56' then 'class1' WHEN '43' then 'class2' else 'other' END as class, 
                CASE substr(number,3,2) WHEN '72' then 'subclass1', WHEN '98' then 'subclass2' ELSE 'other' END as subclass 
        FROM    table 
    ) x
GROUP   BY class, subclass 
HAVING  class != 'other' AND subclass != other 
ORDER   BY class ASC, subclass DESC;