From: johansson.andersson@telia.com   
      
   I practiceing sql question by using Kihlman's SQL webbsite   
   pk = primary key   
   fk = forign key   
      
   I have these tables   
   Firm(FirKey, FirName) pk is FirKey   
   Salary(SalWages, SalTaxYear, FirKey, EmpId) pk is (FirKey, EmpId,   
   SalTaxYear)   fk is FirKey and EmpId   
   Employee(EmpId, EmpFirstName, EmpLastName, EmpPartner,TaxId, EmpLastTaxRaid)   
   pk is EmpId    fk is TaxId, EmpPartner   
   TaxDistrict(TaxId, TaxName, TaxPercentage) pk is TaxId   
      
   The relation is many to many between Firm and Employee so we get an extra   
   relation table in between that we have named Salary   
   We have relation one to many from TaxDistrict to Employee   
   We have also a self join in table Employee for column EmpPartner so   
   EmpPartner will become a forign key here I suppose   
      
   Firm (1) ........(N)Salary(N) .............. (1) Employee(N)   
   ................(1)TaxDistrict   
      
   Here we have a self join   
   Employee.EmpId (1) .................(N) Employee.EmpPartner   
      
   I want to write a SQL question that will give a result that satisfy this   
   question   
   The tax authority suspect person with id number 3 to be a bigamist! Find all   
   information in the Employee table about all his wifes.   
      
   I tries with this   
   SELECT * FROM Employee a1 Employee a2 WHERE a1.EmpId = a2.EmpPartner AND   
   a2.EmpId = 3;   
      
   I get this error when I try the SQL question above.   
   Tables are wrong: The number of tables is correct but at least one table is   
   not correct   
   Conditions are wrong: Conditions are expected but too many have been written   
      
   I also mean that according to the relation straucture an Employee can't have   
   two EmpPartner because that would mean   
   that we have two EmpId with the same primary key   
      
   So can somebody tell me how I should write the SQL question to satisfy this.   
   "The tax authority suspect person with id number 3 to be a bigamist! Find   
   all information in the Employee table about all his wifes".   
   Obviously my SQL question is not correct according to how Kihlman's SQL want   
   to have it.   
      
      
   //Tony   
      
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