I want to do something similar to a database outer join in OPL. Below, I found a way to do it. I test for nullity by using card function. Is there a better way to test for nullity in OPL?

Hi,

you can do that join with the SQL request. But if you do that in OPL , I tend to use sets instead of what you did.

//Tupleset definitionstuple rvPerson {  key string Name;  string StateCode;} tuple rvState {  key string StateCode;  string StateName;}  tuple rvPersonState {  key string PersonName;  string StateName;} //Tupleset datasetof(rvPerson) relPersons = {<"Mark", "BC">, <"Joe", "VT">, <"Bill", "VT">}; setof(rvState) relStates = {<"BC", "Britsh-Columbia">, <"VT", "Vermont">}; setof(rvState) relStatesBis = {<"BC", "Britsh-Columbia">, <"QC", "Québec">};  //Inner Join{rvPersonState} relPersonsStates ={<p.Name, s.StateName> | p in relPersons, s in relStates : p.StateCode==s.StateCode}; //Outer Join{rvPersonState} relPersonsStatesBis ={<p.Name,  (card({s | s in relStatesBis : p.StateCode==s.StateCode})==1?item(relStatesBis,<p.StateCode>).StateName:"null") > | p in relPersons}; /*ResultsrelPersonsStates={PersonName,StateNameMark,Britsh-ColumbiaJoe,VermontBill,Vermont} relStatesBis={PersonName,StateNameMark,Britsh-ColumbiaJoe,nullBill,null}*/execute{  writeln(relPersonsStatesBis );}{string} pStates={p.StateCode | p in relPersons};{string} states={s.StateCode | s in relStatesBis};{string} interStates=pStates inter states;{string} diffStates=pStates diff states;{rvPersonState} relPersonsStatesTer ={<p.Name, s.StateName> | p in relPersons, s in relStatesBis : p.StateCode==s.StateCode && p.StateCode in interStates}union{<p.Name, "null"> | p in relPersons: p.StateCode in diffStates};execute{  writeln(relPersonsStatesTer );}

I want to do something similar to a database outer join in OPL. Below, I found a way to do it. I test for nullity by using card function. Is there a better way to test for nullity in OPL?