Where, From, And Others

WHERE

• the where clause tells us the predicate to pick entries
• relational and logical operators may be used in the predicate
• we can also compare tuples against tuples, i.e. WHERE (A, B) < (C, D)

FROM

• the from clause gives us the domain of the query
• instructor X teaches becomes FROM instructor, teaches
• common attributes get a prefix of at the start of their name

AS

• the AS operator can be used to rename pretty much anything
• it can also be omitted giving the same result. instructor AS T and instructor T do the same thing

ORDER BY

• ORDER BY tells SQL the order to return result rows of the query in
• can be done on multiple attributes for primary and secondary sorting keys
• desc or asc can be put at the end of each sorting key to specify the order of sorting

Between / and

• the between operator is a really dumb way to use \(\geq\) and \(\leq\) together.
• WHERE salary between 90000 and 100000