Simple aggregation
Question
You'd like to get the signup date of your last member. How can you retrieve this information?Schema reminder ▼
Your Answer
Answers and Discussion Show
select max(joindate) as latest from cd.members;
This is our first foray into SQL's aggregate functions. They're used to extract information about whole groups of rows, and allow us to easily ask questions like:
- What's the most expensive facility to maintain on a monthly basis?
- Who has recommended the most new members?
- How much time has each member spent at our facilities?
The MAX aggregate function here is very simple: it receives all the possible values for joindate, and outputs the one that's biggest. There's a lot more power to aggregate functions, which you will come across in future exercises.