computed column in Dataentity

synatx:-  

public static server str methodname()

  {
      str purchid=SysComputedColumn::returnField(dataentityviewstr(Dataentityname),dataEntityDataSourceStr(Dataentityname,Datasourcename),fieldStr(Datasourcename,fieldname));

      return strFmt(@'SELECT TOP 1 from tablename where tablename.fieldname=%1',purchid);

Note:-For lengthy sql stmts dont write direclty here it will show huge errors so pls write first huge sql stmts in SSMS then confirm data correctly then paste in above return statement
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     To declare a string use SysComputedColumn::returnLiteral('string value');