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Best way to write this query

  • January 12, 2009 at 1:14 pm

    #195862

    Hi friends,

    I have 4 tables named

    Places, Sessions, Periods and rules

    Places -> Sessions

    Sessions -> Periods

    Primary Keys :

    Places : Place_Id

    Sessions : Session_Id

    Periods : Period_Id

    Rules will specify the corresponding rules on Places/Sessions/Periods/All

    Sometimes, a rule is defined on Period, sometimes on Sessions, ... on Places

    If a rule is defined on Places and there is no rules on Sessions and Periods,

    all periods will get the same rule as on Places

    if, rule is on Session and there is no rule on Places or Periods, periods will get the same rule as on session.

    Even though, there are rules on Places, Sessions and Periods, Periods will get the own rule not inherited from Sessions or Places.

    What is the best way to write this query.

    My aim is to count the no of records in Periods table with a specific rule.

    Thanks in advance

    Cheers

    Raj

  • January 12, 2009 at 1:38 pm

    #925561

    Write a join query that creates one row per period per rule that applies to it, give the query a Where clause, and use "select count(*)" on the query. That'll get you what you need.

    The rules you outlined are the way to put the joins together.

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