in reply to Re^2: Increase a value inside MySQL query using perl
in thread Increase a value inside MySQL query using perl

That is exactly why I put "first one" and "next one" in "quotes".

And I said the DB does not have the concept of first or next (meaning the next one in an ordened sequence). It is simply not existing in an SQL database whose working is based on set-theory. You have to impose order yourself. So the OP by not defining the ordering was relying on a mechanism that does not exist when he referenced an operation on a sequence of records.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

My blog: Imperial Deltronics
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Re^4: Increase a value inside MySQL query using perl
by chacham (Prior) on Oct 14, 2015 at 20:51 UTC

    I'm just making a technical note here. You are referring to the SQL paradigm, as opposed to a database concept. Instead of mentioning the rdbms and then putting words in quotes, don't mention the rdbms at all. :)

    I will disagree with you partially, about the rdbms not having those concepts. Row order is important to RDBMS's. For example, Oracle has ROWID which is the actual location of the record itself. (And row pointers if they move!) SQL Server organizes table data based on an index (as does Oracle in IOTs.) Other RDBMS likely have similar concepts. So, there is such a concept in the DB, and a program can make use of it too. It's only SQL that doesn't have the concept.

[reply]
      Does a DB wih ROWIDs serve the records in ROWID-sequence?

      Row order should not be important at all, and a DB where this is important is somehow doing it all wrong.

      CountZero

      A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

      My blog: Imperial Deltronics
[reply]

        Does a DB wih ROWIDs serve the records in ROWID-sequence?

        That is a SQL question, not a database question. Databases store data, and order can be very important. SQL is used to retrieve data (via the SQL engine in the RDBMS), and displays it in no specific order, unless told do so.

        But anyway, does ROWID affect retrieval? IIUC, it most certainly does. The table (assuming an index is not used in the query) points to the first data block, which most likely contains the first record, and chains from there. A database that did otherwise would likely be inefficient.

[reply]

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