Database Reference
In-Depth Information
row is denoted as
UQ
row
. Each
UQ
row
is a set of columns and each column is denoted by
UQ
col
.
UQ
rown
(
UQ
colm
) denotes a value stored in
UQ
colm
of
UQ
rown
.
UQ
tablesSize
denotes
the size of
UQ
tables
.
UQ
rowSize
denotes the size of
UQ
row
.
UQ
colNamesSize
denotes the size
of
UQ
colNames
.
UQ
array
denotes a two dimensional array that stores the retrieved rows.
.
5.4
Join Query Algorithm
This algorithm retrieves a combined table rows from two CTTs, two VETs, or a VET
and a CTT based on a common
eld between them using different types of joins
including Left Join, Right Join, Inner Join, Outer Join, Left Excluding Join, Right
Excluding Join, and Outer Excluding Join. In this section, a sample algorithm of the
Left Join is outlined in Algorithm 7.
Denition 7 (Left Join Query Algorithm).
LJQ
leftTable
denotes a left table of the left
join operation.
LJQ
rightTable
denotes a right table of the left join operation. S
leftTable
denotes a string of the SELECT clause for the left table. S
rightTable
denotes a string of the
SELECT clause for the right table. W
leftTable
denotes a string of the WHERE clause for
the left table. W
rightTable
denotes a string of the WHERE clause for the right table.
LJQ
leftPK
denotes a set of primary keys of the left table.
LJQ
rightPK
denotes a set of
primary keys of the right table.
LJQ
rightFK
denotes a set of foreign keys of the right table
refrencing the primary keys of the left table.
LJQ
twoVETs
denotes a row matrix with n rows
and 2 columns. The
rst column stores a
LJQ
twoVETsn
;
0
that denotes a
'
table_row_id
'
of
the
LJQ
leftTable
:
The second column stores a
LJQ
twoVETsn
;
1
that denotes a
'
table_row_id
'
of
the
LJQ
rightTable
:
LJQ
CTTandVET
denotes a row matrix with n rows and 2 columns. The
rst
column stores a
LJQ
CTTandVETn
;
0
that denotes the primary key of the
LJQ
leftTable
which is a
CTT. The second column stores a
LJQ
CTTandVETn
;
1
that denotes a
'
table_row_id
'
of the
LJQ
rightTable
which is a VET.
LJQ
leftRows
denotes a set of rows of the left
table.
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