public function walkSimpleCaseExpression($simpleCaseExpression)
    {
        $sql = 'CASE ' . $this->walkStateFieldPathExpression($simpleCaseExpression->caseOperand);

        foreach ($simpleCaseExpression->simpleWhenClauses as $simpleWhenClause) {
            $sql .= ' WHEN ' . $this->walkSimpleArithmeticExpression($simpleWhenClause->caseScalarExpression);
            $sql .= ' THEN ' . $this->walkSimpleArithmeticExpression($simpleWhenClause->thenScalarExpression);
        }

        $sql .= ' ELSE ' . $this->walkSimpleArithmeticExpression($simpleCaseExpression->elseScalarExpression) . ' END';

        return $sql;
    }