來自where子句中的select子句的原則和別名

Question

我在我的select子句（AVG(u.rating) as avg_rating）中使用了一個別名，然後希望將其添加到我的where子句avg_rating > 3中，但是當我嘗試運行此查詢時，我得到Unknown column 'u3__1' in 'where clause' 。

有沒有人碰巧知道如何讓我的where子句看到別名？這個別名在orderBy中沒有問題，只是不是where。

編輯：（詳情）

上面就是一個例子，但這裏是真正的渲染SQL，不是那麼簡單。我的問題實際上是在一系列條件下帶有別名。而我遇到的別名是生成的日期，它具有重複性，並且不必填寫每個日期字段。所以我發佈了一個簡單的SQL查詢，給了我同樣的問題。

SELECT t.type_id as type_alias, t.* FROM theme as t WHERE t.id > 1 AND type_alias = 3 

這裏是真正的查詢，如果你這麼有興趣：

SELECT t.id AS t__id, t.created_by AS 
t__created_by, t.type_id AS 
t__type_id, t.url_slug AS t__url_slug, 
t.name AS t__name, t.description AS 
t__description, t.summary AS 
t__summary, t.start_month AS 
t__start_month, t.start_day AS 
t__start_day, t.start_year AS 
t__start_year, t.duration_unit AS 
t__duration_unit, t.duration_length AS 
t__duration_length, t.is_active AS 
t__is_active, t.is_public AS 
t__is_public, t.needs_moderation AS 
t__needs_moderation, t.recurrence AS 
t__recurrence, t.tag_string AS 
t__tag_string, t.date_created AS 
t__date_created, t.date_updated AS 
t__date_updated, AVG(t2.rating) AS 
t2__0, IF(t.recurrence = "none", 
STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, t.start_year), "%m%d%Y"), 
(IF(STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, YEAR(NOW())), "%m%d%Y") > 
NOW(), 
STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, YEAR(NOW())), "%m%d%Y"), 
STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, (YEAR(NOW())+1)), 
"%m%d%Y")))) AS t__1, (COUNT(u.id) + 
COUNT(e.id)) AS u__2 FROM theme t LEFT 
JOIN theme_rating t2 ON t.id = 
t2.theme_id LEFT JOIN 
user_saves_themes u ON t.id = 
u.theme_id LEFT JOIN event e ON 
((e.is_active = 1 AND e.theme_id = 
t.id)) WHERE t.id IN ('3', '2', '1') 
AND (IF(t.recurrence = "none", 
STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, t.start_year), "%m%d%Y"), 
(IF(STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, YEAR(NOW())), "%m%d%Y") > 
NOW(), 
STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, YEAR(NOW())), "%m%d%Y"), 
STR_TO_DATE(CONCAT(t.start_month, 
t.start_day, (YEAR(NOW())+1)), 
"%m%d%Y")))) >= 
FROM_UNIXTIME(1278001295) AND 
t.is_public = ? AND t.is_active = ?) 
GROUP BY t.id ORDER BY t__1 

Answer 1

看看這個：

http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html

標準SQL不允許在WHERE子句中的列別名引用。 此限制是因爲在WHERE子句爲 求值時，列值可能尚未確定。例如，對於 示例，以下查詢是非法的：

要麼您必須添加HAVING子句或在WHERE子句中重複您的別名。

Answer 2

嘗試具有替代的位置。