[DISCUSSION] "SET PROPERTY" as SQL command

[Ruslan Zasukhin]

Hi All,

We think now on the next SQL command:

    Set Property of Something to SomeValue.
    

1) we have global properties. Mainly this is for Vserver.

        SET cacheSize = 10
        GET cacheSize


2) It looks that Database can have own properites.

        SET DbCustomers.DateFormat = 'MDY'
        SET DbCustomers.DateSep = '/'
        SET DbCustomers.TimeSep = ':'

        GET DbCustomers.DateFormat


3) also we can propagate this to Table and field Levels:

        SET tblPerson.Property = value

        SET fldName.Property = value
        SET tblPerson.fldName.Property = value


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PROBLEM: as you see just SET is not enough.
        because we do not have effective way to differ db name from
        table name


So it looks as we need syntax as

        SET Property = Value    // for GLOBAL properties

        SET DATABASE PROPERTY dbName.property = value
        SET TABLE PROPERTY  tblName.property = value
        SET FIELD PROPERTY  tblName.property = value


        GET DATABASE PROPERTY dbName.property
        GET TABLE PROPERTY  tblName.property
        GET FIELD PROPERTY  tblName.property

* If we do SET PORPERTY but object do not have such property yet, then it
must be created.

* To drop property we need to have commands as

        DROP DATABASE PROPERTY dbName.property
        DROP TABLE PROPERTY  tblName.property
        DROP FIELD PROPERTY  tblName.property

* What about plural form, when I want SET/GET few properties in one STEP?
   Well, for SET it looks easy:

        SET DATABASE PROPERTY DbCustomers.DateFormat = 'MDY',
                               DbCustomers.DateSep = '/'
                               DbCustomers.TimeSep = ':'


* For GET on single property....
    GET returns some value, so we cannot use it with DB.Sqlexecute().
    Therefore it should be used with SqlSelect() ?
    also not very nice...

* BTW, may be create special kind of call for case when ONLY ONE value is
expected in result? There are some kinds of such SELECTs and it is annoying
work with cursors just to extract one value. So may be:

        SqlGetValue( SqlString ) as VARIANT

Example:
    
        VARIANT v = SqlGetValue( "SELECT max(a) FROM T" );
and
        VARIANT v = SqlGetValue( "GET TABLE PROPERTY tblPerson.property" );


For languages that do not have VARIANT, we can use
                        SqlGetIntValue(), SqlGetStrVlue();


----------------------
At last of end:

    * Do we need these Database/Table/Field properties feature?
    * well for Database this properties already exists in Valentina...
    
    * Hmm, may be field properties also?
      Look on this command:
           SET FIELD PROPERTY fldName.MaxLength = 60
            
      some kind of simple ALTER TABLE?  :-)


So what you think guys ?
Anybody have dream about this? If yes then please tell us WHY.

This is not RDBMS feature.
This feature IMHO DB closer to Object-Relational.
The main advantage of it -- USER/DEVELOPER can create properties on the fly
self. And they will be stored inside of .vdb file, i.e. In the DATABASE
STRUCTURE.


-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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