mySQL SELECT不止一个

Question

i have a table with colums section number like 1 , 2 , 3 etc and room number 1000, 2000, 3000, etc. Room # 2000 is being used by sections 2 and 3.

I want a SQL code to select the rooms that being shared by more than one section. Please note that I have another column called days (Sat, Sun, Mon..) and there are some rooms that are being used by same section more than once. For example room 2000 is used Mon, Tue. So using count() would not work.

I have tried it

SELECT 
    roomNumber
FROM

    section
having
    count(section_number) > 1

but that didn't work. Please help

PS : I am new to mySQL

Answer 1

尝试

Select roomNumber from section group by roomNumber having count(roomNumber) > 1

Answer 2

You are very close. You are missing the group by clause. Add that after your table declarations and before the having clause.

select   roomNumber
from     section
group by roomNumber
having   count(section_number) > 1;

You may to adjust if you need account for null values.