PostgreSQL Exercises

Previous Exercise

Next Exercise

Update some existing data

Question

We made a mistake when entering the data for the second tennis court. The initial outlay was 10000 rather than 8000: you need to alter the data to fix the error.
Schema reminder ▼
DB schema

Expected Results

facid name membercost guestcost initialoutlay monthlymaintenance
0 Tennis Court 1 5 25 10000 200
1 Tennis Court 2 5 25 10000 200
2 Badminton Court 0 15.5 4000 50
3 Table Tennis 0 5 320 10
4 Massage Room 1 35 80 4000 3000
5 Massage Room 2 35 80 4000 3000
6 Squash Court 3.5 17.5 5000 80
7 Snooker Table 0 5 450 15
8 Pool Table 0 5 400 15

Your Answer Hint Help Save Run Query 


              

            

          

        

      

      

      

      

        

          
Answers and Discussion Show

          
update cd.facilities
    set initialoutlay = 10000
    where facid = 1;          

          

            


The UPDATE statement is used to alter existing data. If you're familiar with SELECT queries, it's pretty easy to read: the WHERE clause works in exactly the same fashion, allowing us to filter the set of rows we want to work with. These rows are then modified according to the specifications of the SET clause: in this case, setting the initial outlay.



The WHERE clause is extremely important. It's easy to get it wrong or even omit it, with disastrous results. Consider the following command:



update cd.facilities
    set initialoutlay = 10000;




There's no WHERE clause to filter for the rows we're interested in. The result of this is that the update runs on every row in the table! This is rarely what we want to happen.
            

          

        

      

      
      

        
Previous Exercise

        

          
        

        
Next Exercise

      

    

      

You can alter existing data using the UPDATE statement.
      

      

        

	  
Keyboard shortcuts:

	  
	  

	  
Other hints: