Results 1 to 4 of 4
  1. #1
    Join Date
    Jun 2008
    Posts
    20

    data type question

    1. read a book, cannot really understand the following sentence:
    "Data types vary from one RDBMS to another, so a user might need to use metadata to establish the data types used by a particular database."

    Is that mean there is a metadata which is portable from one RDBMS to another?

    2. using powerdesigner, confused by its int, integer, int(%n) and integer(%n). and also other tools use all upper case data type. ?????

  2. #2
    Join Date
    Feb 2004
    Location
    One Flump in One Place
    Posts
    14,912
    Is that an exact quote? It doesn't make much sense to me...

    If you need to compare the datatypes between two RDBMSs then consult the documentation. Unless the author meant databases not RDBMSs....

  3. #3
    Join Date
    Jun 2008
    Posts
    20
    Quote Originally Posted by pootle flump
    Is that an exact quote?
    Yes. I copied.

  4. #4
    Join Date
    Feb 2004
    Location
    In front of the computer
    Posts
    15,579
    PowerDesigner is a tool that manipulates more than one database engine (IBM DB2, Microsoft, MySQL, Oracle, Sybase, etc). Each engine implements different datatypes, and some of the engines have datatypes with the same name but different implementation specifics.

    I suspect that the point that the author was trying to make is that the designer should not rely on any particular assumptions (is an INT 16, 32, or 64 bits long, is it signed or unsigned, etc). The long standing assumption among academic modelers is that the modeler is responsible for creating appropriate data types for each attribute (column), then mapping those custom types to what the implementation supports at the time the schema is implemented from the model.

    -PatP

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •