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36 Cards in this Set

  • Front
  • Back
repeating groups
multiple entries
relational database
collection of relations
qualify
combining a column name with a table name, i.e. Rep.RepNum
primary key
column or collection of columns that uniquely identifies a given row in the table
query
question represented in a way that the DBMS can recognize
Query by Example
QBE - approach to writing queries that is visual - using onscreen grids and controls
design grid
area where you specify the format of your output
criteria
conditions that data must satisfy
comparison operator/relational operator
>,<,=
compound criteria/compound conditions
multiple comparisons used to select values
computed field
field that is the result of a calculation
aggregate functions
count, sum avg, max, min etc.
grouping
creating groups of records that share some common characteristics
sort key
field on which the records or sorted
major sort key
first sort key in a series of keys (farthest left)
minor/secondary sort key
less important sort - sorted after primary
join line
line that indicates how tables are related
update query
makes a change to all records that satisfy the given criteria
Delete query
deletes all the records satisfying the criteria entered
make-table query
creates a new table using the query results
relational algebra
theoretical way of manipulating a relational database - operations that work on multiple tables
SELECT command
retrieves certain rows from a table
SELECT Customer WHERE CustomerNum=282
GIVING Answer
(creates a new table called answer from the row where customer number is 282)
PROJECT
Takes a vertical subset (columns) of a table

Uses OVER
PROJECT Customer OVER (CustomerNum, CustomerName)
GIVING Answer
Creates a table named answer that contains Customer Number & Name columns
JOIN command
command that joins tables based on matching values
JOIN Customer Rep
WHERE Customer.RepNum=Rep.RepNum
GIVING temp

PROJECT Temp OVER (CustomerNum, CustomerName, RepNum)
GIVING Answer
Joins Customer and Rep using the RepNum attribute and takes customer number name and repnumber columns and puts them in a new table
outer Join
unmatched records are included and the values of the fields are null for records that do not have commonalities
Union
Contains all rows in either A or B and all rows in both
Intersection
Contains all rows common to both A and B
difference
Set of all rows that are in A but not B
Union Compatable
Same number of Columns and they represent the same data
UNION Tbl1 WITH Tbl2 GIVING Answer
Creates table answer from the UNION of Tbl 1 and 2
INTERSECT Tbl1 WITH tbl2 GIVING Answer
Creates table Answer from the intersection of 1 and 2
SUBTRACT Tbl1 FROM Tbl2 GIVING Answer
Difference between 2 tables
PRODUCT
concatenating every row in table 1 with every row in table 2