PostgreSQL Exercises

Previous Exercise

Next Exercise

List each member's first booking after September 1st 2012

Question

Produce a list of each member name, id, and their first booking after September 1st 2012. Order by member ID.
Schema reminder ▼
DB schema

Expected Results

surname firstname memid starttime
GUEST GUEST 0 2012-09-01 08:00:00
Smith Darren 1 2012-09-01 09:00:00
Smith Tracy 2 2012-09-01 11:30:00
Rownam Tim 3 2012-09-01 16:00:00
Joplette Janice 4 2012-09-01 15:00:00
Butters Gerald 5 2012-09-02 12:30:00
Tracy Burton 6 2012-09-01 15:00:00
Dare Nancy 7 2012-09-01 12:30:00
Boothe Tim 8 2012-09-01 08:30:00
Stibbons Ponder 9 2012-09-01 11:00:00
Owen Charles 10 2012-09-01 11:00:00
Jones David 11 2012-09-01 09:30:00
Baker Anne 12 2012-09-01 14:30:00
Farrell Jemima 13 2012-09-01 09:30:00
Smith Jack 14 2012-09-01 11:00:00
Bader Florence 15 2012-09-01 10:30:00
Baker Timothy 16 2012-09-01 15:00:00
Pinker David 17 2012-09-01 08:30:00
Genting Matthew 20 2012-09-01 18:00:00
Mackenzie Anna 21 2012-09-01 08:30:00
Coplin Joan 22 2012-09-02 11:30:00
Sarwin Ramnaresh 24 2012-09-04 11:00:00
Jones Douglas 26 2012-09-08 13:00:00
Rumney Henrietta 27 2012-09-16 13:30:00
Farrell David 28 2012-09-18 09:00:00
Worthington-Smyth Henry 29 2012-09-19 09:30:00
Purview Millicent 30 2012-09-19 11:30:00
Tupperware Hyacinth 33 2012-09-20 08:00:00
Hunt John 35 2012-09-23 14:00:00
Crumpet Erica 36 2012-09-27 11:30:00

Your Answer Hint Help Save Run Query 


              

            

          

        

      

      

      

      

        

          
Answers and Discussion Show

          
select mems.surname, mems.firstname, mems.memid, min(bks.starttime) as starttime
	from cd.bookings bks
	inner join cd.members mems on
		mems.memid = bks.memid
	where starttime >= '2012-09-01'
	group by mems.surname, mems.firstname, mems.memid
order by mems.memid;          

          

            


This answer demonstrates the use of aggregate functions on dates.  MIN works exactly as you'd expect, pulling out the lowest possible date in the result set.  To make this work, we need to ensure that the result set only contains dates from September onwards.  We do this using the WHERE clause.



You might typically use a query like this to find a customer's next booking.  You can use this by replacing the date '2012-09-01' with the function now()
            

          

        

      

      
      

        
Previous Exercise

        

          
        

        
Next Exercise

      

    

      

Take a look at the MIN aggregate function
      

      

        

	  
Keyboard shortcuts:

	  
	  

	  
Other hints: