SQL Select and Relational Algebra

SELECT

SELECT fields

FROM tables

WHERE conditions

GROUP BY fields

HAVING conditions

ORDER BY fields

SELECT *

FROM expeople

SELECT name (Projection)

FROM expeople

SELECT name, age

FROM expeople

SELECT DISTINCT name

FROM expeople

SELECT sex AS gender (renaming)

FROM expeople

SELECT *

FROM expeople

WHERE age = 17 (selection)

= Equal

<> Not Equal

> Greater Than

< Less Than

>= Greater Than or Equal

<= Less Than or Equal

IS NULL

IS NOT NULL

LIKE

NOT LIKE

%

_

New% will match Newark, New York, etc.

_ow will match Cow, Bow, Now, etc.

AND

OR

SELECT *

FROM expeople

WHERE age = 17 OR name = ‘JoJo’

SELECT *

FROM expeople

ORDER BY expeople.id desc

(or can use asc)

SELECT sum(nums)

FROM exnum

count() Total number of items

sum() Sum of the items

avg() Average of the items

min() Smallest of the items

max() Biggest of the items

SELECT name, sum(number)

FROM exnum

GROUP BY name

SELECT sum(number)

FROM exnum

GROUP BY name

HAVING sum(nums) > 30

SELECT expeople.*, exjobs.*

FROM expeople, exjobs

(cartesian product)

SELECT expeople.*, exjobs.*

FROM expeople, exjobs

WHERE expeople.id = exjobs.jid(equi-joins)

SELECT *

FROM expeople

WHERE name = ‘JoJo’

UNION (union)

SELECT *

FROM expeople

WHERE age = ‘17’

SELECT *

FROM expeople

WHERE name = ‘Mike’

INTERSECT(intersection)

SELECT *

FROM expeople

WHERE age = ‘17’

SELECT *

FROM expeople

WHERE name = ‘Mike’

MINUS (set-difference)

SELECT *

FROM expeople

WHERE age = ‘17’

DONE