HIT334. Week 2. Some Definitions. Set : A collection of objects that contain NO duplicates Relation : Table, a set of tuples Tuple : Row in a table, a collection of attributes Attribute : Column Heading, an actual role played by Domain
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Projection:Used to produce, from relation R, a new relation that has only some of R’s attributes.
Denoted as A1,A2..AnR , which gives a relation that only has the columns for attributes A1, A2…An
title, year, studio MOVIE =
inColour Movie =
title, year, studio(length > 100 AND studioName = ‘Fox’ (MOVIE))
Instead of nesting, you can explicitly show a sequence of operations:
TEMP <- length > 100 AND studioName = ‘Fox’(MOVIE))
RESULT<- title, year, studio(TEMP)
SELECT title, year, studio
WHERE length > 100
AND studioname = ‘FOX’
R X S =
To find the tuples that agree on the value in column B :
TEMP <- R X S
RESULT <- σR.B = R.S TEMP
To Retrieve the manager of each Department:
DEPT_MGR DEPARTMENT MGRSSN=SSN (EMPLOYEE)
What if you only wanted the Manger for the Administration Department?