mysql - 如何将时间间隔代码添加到 SQL

Question

SELECT COUNT(*) AS cnt FROM ( (SELECT 'used' FROM b_names_1) UNION ALL (SELECT 'used' FROM b_names_2)) AS t WHERE 'used' = 1

这个码字很好..

但我想按时间间隔对结果进行排序，所以当我试图在底部添加这一行时，它不起作用：

AND registration_date_time >= STR_TO_DATE( '2013-01-28 00:00:00', '%Y-%m-%d %H:%i:%s' ) AND registration_date_time < STR_TO_DATE( '2013-02-02 00:00:00', '%Y-%m-%d %H:%i:%s' )

这段代码看起来像这样：

SELECT COUNT(*) AS cnt FROM ( (SELECT 'used' FROM b_names_1) UNION ALL
(SELECT 'used' FROM b_names_2)) AS t
WHERE 'used' = 1 AND registration_date_time >= STR_TO_DATE( '2013-01-28 00:00:00', '%Y-%m-%d %H:%i:%s' ) AND registration_date_time < STR_TO_DATE( '2013-02-02 00:00:00', '%Y-%m-%d %H:%i:%s' )

它给了我以下错误：#1054 - 'where 子句'中的未知列'registration_date_time'

知道如何正确地将日期代码实现到 SQL 中吗？

Answer 1

这些列必须来自某个地方，将它们添加到内部查询中：

SELECT COUNT(*) AS cnt 
FROM ( 
    (SELECT 'used', registration_date_time FROM b_names_1) 
    UNION ALL
    (SELECT 'used', registration_date_time FROM b_names_2)
) AS t
WHERE 'used' = 1 
AND registration_date_time >= STR_TO_DATE( '2013-01-28 00:00:00', '%Y-%m-%d %H:%i:%s' ) 
AND registration_date_time < STR_TO_DATE( '2013-02-02 00:00:00', '%Y-%m-%d %H:%i:%s' )