2.1.26. Aggregate functions
- Run over groups of tuples
- Takes a projected attribute list as an argument
- Produce relation with single tuple
- SUM, MAX, MIN, AVG, COUNT
- e.g. AggFunc over all tuples
- SELECT SUM(SALARY), MAX(SALARY), MIN(SALARY)
- FROM EMPLOYEE;
- Single attribute lists (distinct values)
- Multi-attribute lists (granularity of distinct values by pairing)