The method by which a database management system locates physical data.
Often used with the GROUP BY and HAVING clauses, aggregate functions generate one summary value from a group of values in a specified column. Aggregate functions include AVG, SUM COUNT, COUNT(*), MIN, and MAX.
A temporary name given to a table (in the FROM clause). Here are two examples of how it can be used:
select au_id, a.city, p.city, pub_id from authors a, publishers p where au_lname like 'P%' select a.au_id, b.au_id from authors a, authors b where a.zip = b.zip
In the first example, the alias eliminates the need to type the whole table name as a qualifier for each column name that could belong to either table ...