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Conference ilbbak::ibi_focus

Title:FOCUS, from INFORMATION BUILDERS
Moderator:ZAYIUS::BROUILLETTE
Created:Thu Feb 19 1987
Last Modified:Mon May 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:615
Total number of notes:1779

311.0. "RDB Master File Descriptions (MFDs)" by AYOV33::FBRIDGEFORD (OH! The hills.... ) Thu Feb 08 1990 05:14

    
    Currently we are integrating a newly designed Rdb database with
    focus. The question is:
    
    When creating the Master File Description, Segments relate to tables.
    We have tables that have the same field name. Can FOCUS have the
    same field name in different segments within one Master File
    Description? ( or can the MFDs point to tables within a database
    rather than the database itself? )
    
          
    
    Thanks
    
    Fraser
T.RTitleUserPersonal
Name		DateLines
311.1ALIAS the same, FIELDNAME uniquePLOP::COYLEThu Feb 08 1990 08:3711

  Fraser,

      When you create a Master File Description for an RDB database containing
multiple relations, you can have have ALIAS fields that will be the same
in more than one segment, but the FOCUS manuals specify that the FOCUS
FIELDNAME parameter should be unique within the file.


                                          KC
311.2ArgAYOV33::FBRIDGEFORDOH! The hills.... Thu Feb 08 1990 10:445
    That's what I was afraid of!
    
    Thanks
     
    Fraser_B
311.3Questions, questions, questions.AYOV33::FBRIDGEFORDOH! The hills.... Fri Feb 16 1990 09:5714
    The Rdb Interface Manual states 
    
    "To use the embedded join facility, you add the keyword PARENT to
    all segments other than the first one defined in the Master File
    ---
    Description."
    
    Is this valid, or can you have more than one parent within the Master
    File Description, or will I need multiple Master File descriptions
    for the same database?
    
    Thanks
    
    Fraser_B
311.4AYOV33::FBRIDGEFORDOH! The hills.... Mon Feb 19 1990 07:474
    Re .3 Anyone?
    
    Fraser_B
311.5Getting to the root of the problem ?SHAPES::CARSEDTue Feb 20 1990 06:2649
    
    You can have as many 'PARENTS' as you like in a Master File
    Description as long as there is just **ONE** parent root segment
    i.e. FOCUS has only one entry point into the segment tree structure.
    For example, consider the following structure:
    
    			+--------+
                        |        |
                        | SEG01  |      <=== ONE PARENT ROOT SEGMENT
                        |        |
    			+--------+
                            |
                            |--------------------|
                            |                    |
    			+--------+           +--------+
                        |        |           |        |
                        | SEG02  |           | SEG03  |
                        |        |           |        |
    			+--------+           +--------+
                            |
                            |
                            |
    			+--------+
                        |        |
                        | SEG04  |
                        |        |
    			+--------+
                            |
                            |
                            |
    			+--------+
                        |        |
                        | SEG05  |
                        |        |
    			+--------+
    
    
    The following statements are true:
    
    1.		SEG01 is the PARENT of SEG02
    2.		SEG01 is the PARENT of SEG03
    3.		SEG02 is the PARENT of SEG04
    4.		SEG04 is the PARENT of SEG05
    
    This could be extrapolated into a much more complicated example but,
    ** as long as there is still only one root segment in the structure **
    everything should work fine.
    
    David.
311.6Maybe multiple MAS/ACX files - perf.IJSAPL::WOODROWFather of DRSSun Feb 25 1990 13:0421
    Re .3
    
    There are definitely performance implications associated with the
    choice of the "root segment" w.r.t. Rdb. FOCUS (at least thru
    5.2.3) performs its own "join" for all segments not in a strick
    hierarchical downward order in the MAS/ACX file, except when only the
    "upward" segment is queried. Thus, if a query would perform much better
    by using a different root, then you might well have need of multiple
    MAS/ACX combinations.
    
    An example from PERSONNEL with EMPLOYEES as root and containing
    JOBS. A query for employee name where JOB_TITLE equals "Company
    President" will read every single employee record and all related
    JOB_HISTORY records and JOBS records to satisfy the query. Judicious
    use of RDMS$DEBUG_FLAGS is recommended (especially "B" to see the query
    passed to Rdb).
    
    Hope this has been of some help.
    
    Peter