如何在SQL中为别名列赋予条件

Question

如何在此查询中为具有别名的列指定条件？

我的查询：

select
cnt.id as content_id,
cnt.title as content_title,
cnt.introtext,
cnt.fulltext,
cnt.ordering,
cnt.images,
cnt.alias,
cnt.state,
cnt.catid,
f.item_id,
cat.id as cat_id,
cat.title as cat_title,
max(case when f.field_id = 1 then f.value end) as inslider,
max(case when f.field_id = 2 then f.value end) as sliderquote
from snm_fields_values f
join snm_content cnt
on cnt.id = f.item_id
join snm_categories cat
on cnt.catid = cat.id
where cnt.state = 1
and f.value = 'ja'
group by f.item_id
order by f.item_id, inslider

这将返回以下内容：

sliderquote为NULL，因为它检查f.value是否等于它从未执行过的'ja'。如果我删除条件，我得到该行中的正确数据，但我需要条件。

我怎么还能拥有它并且只将它应用于sliderquote？

AND sliderquote = 'ja'不起作用，因为SQL不会像我学到的那样读取别名。

我能做什么？

Answer 1

我想你可能需要一个嵌套请求，如下所示：

SELECT *
FROM   (SELECT cnt.id    AS content_id,
               cnt.title AS content_title,
               cnt.introtext,
               cnt.fulltext,
               cnt.ordering,
               cnt.images,
               cnt.alias,
               cnt.state,
               cnt.catid,
               f.item_id,
               cat.id    AS cat_id,
               cat.title AS cat_title,
               Max(CASE
                     WHEN f.field_id = 1 THEN f.value
                   END)  AS inslider,
               Max(CASE
                     WHEN f.field_id = 2 THEN f.value
                   END)  AS sliderquote
        FROM   snm_fields_values f
               JOIN snm_content cnt
                 ON cnt.id = f.item_id
               JOIN snm_categories cat
                 ON cnt.catid = cat.id
        WHERE  cnt.state = 1
        GROUP  BY f.item_id
        ORDER  BY f.item_id,
                  inslider)T
WHERE  T.sliderquote = 'ja'