ch7-ppt Flashcards
(9 cards)
1
Q
JOIN
A
bring together data from more than one table into one table
2
Q
common domain
A
one foreign key and one primary key will be the same. computers way of matching relationships
3
Q
two approaches of join
A
explicit join and subquery
4
Q
inner join
A
aka equi-join. match based on equality in common columns. only matched columns are returned.
ON column=column
5
Q
outer join
A
all records returned from one table, whether they match or not
6
Q
subquery
A
place an inner query within a WHERE or HAVING clause of another outer query.
outer query is what is actally displayed
one query output is put into one query input
7
Q
two types of subqueriese
A
1-noncorrelated
2-correlated
8
Q
noncorrelated subquery
A
do not depend on data from outer query
9
Q
correlated subquery
A
use formula on the data of outer query
