sql - 与多个日期相关的查询

Question

我仍然开始涉足 SQL。我在查询日期并将它们分组时遇到问题。我想对日期进行分组。并从此日期显示特定日期范围内的访问名称和类型。

从下面的例子说，我想查询从01/01/2012 到 31/12/2012范围内访问的人，访问类型为4

Answer 1

SELECT DISTINCT NAME 
FROM YOUR_tABLE 
WHERE (TYPE_OF_VISIT = 4) AND (DATE_OF_VISIT BETWEEN ? AND ?)

如果您希望每个客户在此范围内第一次访问，那么您应该像这样尝试

SELECT DISTINCT T1.NAME, T1.DATE_OF_VISIT 
FROM YOUR_TABLE T1
WHERE (T1.TYPE_OF_VISIT = 4) AND (T1.DATE_OF_VISIT BETWEEN ? AND ?)
AND T1.DATE_OF_VISIT = 
(SELECT MIN (T2.DATE_OF_VISIT) FROM YOUR_TABLE T2 WHERE T1.NAME=T2.NAME AND 
(T2.DATE_OF_VISIT BETWEEN ? AND ?))

Answer 2

你可以试试：

select Name, Type_of_visit
from Appointment_table
where Date_of_visit between '2012-01-01 00:00:00' and '2012-12-31 23:59:59'
and Type_of_visit = 4;

如果您想对结果进行分组（和汇总访问）：

select Name, Type_of_visit, COUNT(Type_of_visit) as Total_visits
from Appointment_table
where Date_of_visit between '2012-01-01 00:00:00' and '2012-12-31 23:59:59'
and Type_of_visit = 4
group by Name, Type_of_visit;

按日期分组将为您提供每个唯一日期的一行，从您的示例输出来看，这看起来不像您想要的。

Answer 3

如果 Date_of_visit 列不包含任何时间部分（即仅日期）。您可以执行以下操作

SELECT NAME, TYPE_OF_VISIT
FROM appointment 
WHERE Type_of_visit = 4 
AND Date_of_visit >= '01/01/2012 ' 
AND Date_of_visit <= '31/12/2012'
GROUP BY NAME