Question

我试图从酒店数据库回答以下问题

显示2011日历年每个月的预订数量。

这是我到目前为止所提出的。

SELECT booking_no,
       date_in,
       Count(*)
FROM   booking
WHERE  date_in >= '01-jan-11'
       AND date_in <= '31-dec-11'
GROUP  BY booking_no,
          date_in
ORDER  BY date_in;

这些是数据库标题

访客

Name Type
--------------------- ------------
GUEST_NO 
SURNAME 
GIVEN 
DOB 
SEX 
HOME_PHONE 
WORK_PHONE 
FAX 
ADDRESS 
SUBURB 
STATE 
POSTCODE

房间

Name Type
--------------------- ------------
ROOM_NO 
FLOOR_NO 
SPA_BATH 
NUM_BEDS 
PRICE 
LINKED_ROOM_NO )

BOOKING

Name Type
--------------------- -----------
BOOKING_NO 
GUEST_NO 
ROOM_NO
DATE_IN 
DATE_OUT

Answer 1

您想要每月的号码，所以

select month(date_in), count(*) 
from booking 
where year(date_in)=2011
group by month(date_in)
order by month(date_in);

Answer 2

试试他的：

SELECT Count(booking_no) bookings,
       Month(date_in)    month_name
FROM   booking
WHERE  date_in >= '01-jan-11'
       AND date_in <= '31-dec-11'
GROUP  BY Month(date_in)
ORDER  BY Month(date_in);

不要在where子句中执行“year(date_in)=2011”，如果您在date_in列上有索引，则会阻止使用索引。如果你没有，那没关系。

Answer 3

您需要的是MONTH功能。这在大多数数据库引擎中都是相同的。所以试试

SELECT booking_no, Month(date_in), Count(booking_no)

和

GROUP BY Month(date_in)
ORDER BY Month(date_in);

您还可以使用YEAR：

简化where子句

WHERE Year(date_in) = 2011

共：

SELECT Month(date_in),
       Count(*)
FROM   booking
WHERE  Year(date_in) = 2011
GROUP  BY Month(date_in)
ORDER  BY Month(date_in);

sql查询酒店数据库

3 个答案: