1
Aggregate functions (denoted by script F or script A) perform operations like sum, average, maximum, minimum, and count on numerical values and tuples in a database.
2
Grouping allows tuples in a relation to be categorized into groups before applying aggregate functions to each group.
3
Recursive closure operations are applied to recursive relationships, allowing queries across multiple levels such as finding employees supervised at level 1 and level 2.
4
Inner joins eliminate non-matching tuples, leading to information loss, which is avoided by using outer joins.
5
Left outer join keeps all tuples from the left relation and matching tuples from the right, padding non-matches with null values.
6
Right outer join keeps all tuples from the right relation and matching tuples from the left, padding non-matches with null values.
7
Full outer join keeps all tuples from both relations, padding non-matching tuples with null values on both sides.
8
Outer union is used to combine partially compatible relations that share the same degree but have differing attribute domains, padding missing values with nulls.