private static void Visit(SqlExpression exp, bool equals = false)
{
var visitor = new SqlExpressionVisitor();
var result = exp.Accept(visitor);
Assert.IsType(exp.GetType(), result);
Assert.Equal(equals, result.Equals(exp));
result = visitor.Visit(exp);
Assert.IsType(exp.GetType(), result);
Assert.Equal(equals, result.Equals(exp));
}