09 September 2009

Basic Structure of SQL

The basic structure of an SQL expression consists of three clauses:
  • The select clause corresponds to the projection operation of the relational algebra. It is used to list the attributes desired in the result of a query.
  • The from clause corresponds to the Cartesian-product operation of the relational algebra. It lists the relations to be scanned in the evaluation of the expression.
  • The where clause corresponds to the selection predicate of the relational algebra. It consists of a predicate involving attributes of the relations that appear in the from clause.

5 comments:

  1. Good post and straight to the point. I am not sure if this is truly the best place to ask but do you folks have any thoughts on where to get some professional writers.Oracle Goldengate

    ReplyDelete
  2. Hi! I am a digital marketer. The previous seo guy working for my client left a spammy comment at your blog with the username Janice Rafael which links to my client's site.
    Such comments are or might cause serious damage to my client's site with respect to SEO which is why I am request you here by to remove it asap.
    If you don't remove it by 12:00 am, Pacific Standard Time, 2nd January 2014, we will have use Google's Disavow Tool to get back-link removed and, sorry to say this, but Google may not look too nicely upon you either for not having removed the comment. Thanks in advance for your cooperation.

    ReplyDelete
  3. Good information shared about database..
    Shoofi

    ReplyDelete
  4. Interesting!! I never considered it that way. I came across this site as of late which I suppose it will be an incredible utilization of new plans and informations.
    Oracle Remote Database Administration

    ReplyDelete