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Using join indexes
The join hierarchy in query resolution
One-to-many relationship
154
You can set the frequency of these messages with the
option, and override the option value in either the
command. For examples of these messages, see "Interpreting
LOAD TABLE
notification messages" on page 187.
Adaptive Server IQ can use the same join index to resolve a query that involves
the full join relationship specified in the join index, or a query that involves any
contiguous subset of that relationship; you do not have to create separate join
indexes for the subset relationships.
For example, assume that join index
Figure 4-1. Adaptive Server IQ can use join index
queries that involve:
•
The entire relationship
•
Table
to Table
A
D
•
Table
to Table
to Table
A
D
•
Table
to Table
B
D
•
Table
to Table
to Table
B
D
•
Table
to Table
D
F
•
Table
to Table
C
E
•
Table
to Table
E
F
•
Table
to Table
to Table
C
E
However, Adaptive Server IQ cannot use join index
against, for example, Table
In a one-to-many join relationship, one row in one table potentially matches
with one or more rows in another table, and there is not more than one row in
the first table that matches with the same row(s) in the second table. For this to
be true, the values in the join column in the first table must be unique.
It is possible that either table has no match on the other table. This constitutes
an outer join and is fully supported. For more information, see the Introduction
to Adaptive Server IQ.
CREATE DATABASE
joins the tables illustrated in
ABCDEF
ABCDEF
F
F
F
ABCDEF
to Table
.
E
D
NOTIFY_MODULUS
or
to resolve any
to resolve queries
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