code: package it.unibz.inf.ontop.model.term.functionsymbol.db.impl;
  
  import com.google.common.collect.ImmutableList;
  import it.unibz.inf.ontop.model.term.ImmutableFunctionalTerm;
  import it.unibz.inf.ontop.model.term.ImmutableTerm;
  import it.unibz.inf.ontop.model.term.TermFactory;
  import it.unibz.inf.ontop.model.term.functionsymbol.db.DBIsTrueFunctionSymbol;
  import it.unibz.inf.ontop.model.type.DBTermType;
  
  import java.util.Optional;
  import java.util.function.Function;
  
  public class SQLServerBooleanDBIfElseNullFunctionSymbolImpl extends BooleanDBIfElseNullFunctionSymbolImpl {
  
      private static final String TEMPLATE = "IIF(%s,%s,NULL) = 1";
  
      protected SQLServerBooleanDBIfElseNullFunctionSymbolImpl(DBTermType dbBooleanType) {
          super(dbBooleanType);
      }
  
      @Override
      public String getNativeDBString(ImmutableList<? extends ImmutableTerm> terms,
                                      Function<ImmutableTerm, String> termConverter, TermFactory termFactory) {
          return String.format(TEMPLATE,
                  termConverter.apply(terms.get(0)),
                  termConverter.apply(unwrapIsTrue(terms.get(1))));
      }
  
      /**
       * Equalities are not supported by this dialect as a valid second argument of IIF, so IS_TRUE is unwrap.
       */
      private ImmutableTerm unwrapIsTrue(ImmutableTerm term) {
          return Optional.of(term)
                  .filter(t -> t instanceof ImmutableFunctionalTerm)
                  .map(t -> (ImmutableFunctionalTerm) t)
                  .filter(t -> t.getFunctionSymbol() instanceof DBIsTrueFunctionSymbol)
                  .map(t -> t.getTerm(0))
                  .orElse(term);
      }
  }
  