public void Existing()
{
var result = AdminQuery.Assign("a", SqlExpression.Constant(7689));
Assert.IsNotNull(result);
Assert.IsInstanceOf<NumericType>(result.Type);
var variable = AdminQuery.Context.FindVariable("a");
Assert.IsNotNull(variable);
Assert.IsNotNull(variable.Expression);
Assert.IsNotNull(variable.Evaluate(AdminQuery));
var value = ((SqlNumber) variable.Evaluate(AdminQuery).Value).ToDouble();
Assert.AreEqual(7689, value);
}