Kbase 17691: Different types of joins in Actuate
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
5/10/1998 |
|
Different types of joins in Actuate
INTRODUCTION:
============
When you select more than one table Actuate AUTOMATICALLY 'joins'
to link related tables if it can determine the columns on which the
tables are joined. A join is a SQL operation that combines records
from two tables (or more) and returns them in a result set based on
the values in the join field.
WHY YOU NEED TO KNOW THIS:
=========================
To decide where joins should occur, Actuate applies these criteria
in order:
1) The relationship information, if available, in the data
dictionary of a database
2) Primary and foreign keys
3) Matching column names and types
PROCEDURAL APPROACH:
===================
You can also establish joins using the Query Editor. The types of
join depends on your DBMS. The Actuate Query Editor supports the
following types of joins.
INNER JOIN - Returns records from two tables where the values of the
joined fields have a specified relationship, such as
equal or greater than.
LEFT OUTER JOIN - Returns records from the leftmost table even if
there are no matching values in the other table.
RIGHT OUTER JOIN - Returns records from the rightmost tabel even if
there are no matching values in the other table.
As you create joins, Actuate automatically begins writing the
WHERE-clause of the SQL SELECT statement.
ONLINE PROCEDURES OR UTILITIES:
==============================
REFERENCES TO WRITTEN DOCUMENTATION:
===================================
Actuate Developer WorkBench 2.0 - 'Building Reports' - page 103
mhu 02/13/98
Progress Software Technical Support Note # 17691