Rating orders

This example demonstrates how the different data flow components can be used together, simulating a real-life scenario. In this scenario, we will to read some orders from a csv file, lookup the customer key by using the customer name, write the orders into an orders table and also create a customer rating based on the total amount of purchases.

Schematic overview


In order to recreate this demo, you need a database server. This example will run on any supported database - though every database comes with some database specific particularities. The following code was succesfully tested with Sql Server.

If you are using docker, you can use the following command to create a docker container for Sql Server:

docker run -e "ACCEPT_EULA=Y" -e "SA_PASSWORD=YourStrong@Passw0rd" -p 1433:1433 --name localmssql -d mcr.microsoft.com/mssql/server

You may need to create a login first, and call docker login before you can execute this command. The container can be started with docker start localmssql. This will create a Sql Server database listening on port 1433 for incoming connections. The sysadmin login has the username sa with the password YourStrong@Passw0rd.

You need to create a database called “demo” prior to following this example.

The connection string to connect to this database will look similar like this: Data Source=.;Initial Catalog=demo;Integrated Security=false;User=sa;password=YourStrong@Passw0rd; You probably need to adjust the adress to your needs (e.g. replace “.” with “” to access the database on a different machine).


We need to create the destination table orders and customer_rating as empty table. Also we want a customer table that hold a customer key for our customer names. We could do this manually, or we can use the following ControlFlow Tasks to create these tables:

Settings.DefaultDbConnection = new SqlConnectionManager("Data Source=.;Initial Catalog=demo;Integrated Security=false;User=sa;password=YourStrong@Passw0rd");

TableDefinition OrderDataTableDef = new TableDefinition("orders",
    new List<TableColumn>() {
        new TableColumn("Key", "int",allowNulls: false, isPrimaryKey:true, isIdentity:true),
        new TableColumn("Number","nvarchar(100)", allowNulls: false),
        new TableColumn("Item","nvarchar(200)", allowNulls: false),
        new TableColumn("Amount","money", allowNulls: false),
        new TableColumn("CustomerKey","int", allowNulls: false)

TableDefinition CustomerTableDef = new TableDefinition("customer",
    new List<TableColumn>() {
        new TableColumn("Key", "int",allowNulls: false, isPrimaryKey:true, isIdentity:true),
        new TableColumn("Name","nvarchar(200)", allowNulls: false),

TableDefinition CustomerRatingTableDef = new TableDefinition("customer_rating",
    new List<TableColumn>() {
        new TableColumn("Key", "int",allowNulls: false, isPrimaryKey:true, isIdentity:true),
        new TableColumn("CustomerKey", "int",allowNulls: false),
        new TableColumn("TotalAmount","decimal(10,2)", allowNulls: false),
        new TableColumn("Rating","nvarchar(3)", allowNulls: false)

//Create demo tables & fill with demo data
SqlTask.ExecuteNonQuery("Fill customer table", "INSERT INTO customer values('Sandra Kettler')");
SqlTask.ExecuteNonQuery("Fill customer table", "INSERT INTO customer values('Nick Thiemann')");
SqlTask.ExecuteNonQuery("Fill customer table", "INSERT INTO customer values('Zoe Rehbein')");
SqlTask.ExecuteNonQuery("Fill customer table", "INSERT INTO customer values('Margit Gries')");

Let’s define some POCOs (Plain old component objects) that can hold the data when it goes through the data flow pipeline.

public class Order
    public string Number { get; set; }
    public string Item { get; set; }
    public int CustomerKey { get; set; }
    public string CustomerName { get; set; }
    public decimal Amount { get; set; }

public class Customer
    public int Key { get; set; }
    public string Name { get; set; }

public class Rating
    public int CustomerKey { get; set; }
    [AggregateColumn(nameof(Order.Amount), AggregationMethod.Sum)]
    public decimal TotalAmount { get; set; }

    public string RatingValue => TotalAmount > 50 ? "A" : "F";

Please note that there are attributes above the properties. The attributes MatchColumn/RetrieveColumn are used for the LookupTransformation and GroupColumn/AggregationColumn for the Aggregation. They will be explained later.

The DbColumnMap attribute above the property RatingValue will map the table column Rating in the customer_rating table with corresponding property “RatingValue”. Normally, ETLBox maps columns in source or destinations with properties by matching names. So to make things work by default, the property could have been called “Rating” - but by adding the DbColumnMap attribute, we can define a different name for the property and let it match with the column “Rating” in the table.

Build the pipeline

Now we can construct a pipeline. Let’s start with the source

//Read data from csv file
CsvSource sourceOrderData = new CsvSource("DemoData.csv");
sourceOrderData.Configuration.Delimiter = ";";

Source data will look like this:

4711;Yellow Shoes;30.00$;Sandra Kettler
4712;Green T-Shirt;14.99$;Nick Thiemann
4713;Blue Jeans;29.99$;Zoe Rehbein
4714;White Jeans;29.99$;Margit Gries
4807;Green Shoes;32.00$;Margit Gries

We add a row transformation - and connect it with source. Data will be read from the source and moved into the row transformation. A row transformation will go through each row and modifies it by a given function. Furthermore, a row transformation can change the object type of the input into something different - we use this to transform our string array into our POCO.

//Transform into Order object
RowTransformation<ExpandoObject, Order> transIntoObject = new RowTransformation<ExpandoObject, Order>(
    csvLine =>
        dynamic order = csvLine as dynamic;
        return new Order()
            //Header in Csv: OrderNumber;OrderItem;OrderAmount;CustomerName
            Number = order.OrderNumber,
            Item = order.OrderItem,
            Amount = decimal.Parse(order.OrderAmount.ToString().Replace("€",""), CultureInfo.GetCultureInfo("en-US")),
            CustomerName =  order.CustomerName

Retrieving the customer key

Next we want to find a customer key for the customer name in our csv file. To make this work, we already created a customer table that holds a list of customer names and the corresponding keys.

We now define this customer table as a source for our lookup. A lookup will load data from this source to enrich the data in the flow. The customer data will be loaded into the memory as soon as the first rows arrives at the LookupTransformation.

 //Find corresponding customer id if customer exists in Customer table
DbSource<Customer> sourceCustomerData = new DbSource<Customer>("customer");
LookupTransformation<Order, Customer> lookupCustomerKey = new LookupTransformation<Order, Customer>(sourceCustomerData);

The lookup works because it can gather the required information from the attributes in the Customer object. There, we did define a MatchColumn and a RetrieveColumn attribute. The MatchColumn looked like this: [MatchColumn(nameof(Order.CustomerName)] and was set on the property “Name”. The lookup now knows that any value in the Name must match the property CustomerName in the incoming Order data. If the values of these two properties matches, the attribute [RetrieveColumn(nameof(Order.CustomerKey)] tells the LookupTransformation to push the retrieved value from the source into the property CustomerKey in the Order.

After an Order row has been processed by the lookup, the property CustomerKey holds the value from the Key column the customer table.

Splitting the data

Now we add a multicast - a multicast “doubles” the input into 2 same outputs with the exact same data. This is useful if you want to have additional destination populated with data based on your input. In our scenario we do this because we not only want to store the orders in a order table, but also we want to create some customer rating based on the orders.

//Split data
Multicast<Order> multiCast = new Multicast<Order>();

So now let’s store the orders with the retrieved customer key in the order table. We need a DbDestination for this.

//Store Order in Orders table
DbDestination<Order> destOrderTable = new DbDestination<Order>("orders");

Creating the customer rating

The other output will go into an aggregation block to calculate the customer rating. An aggragation is a non-blocking transformation that can do some basic aggregation: Sum, Min, Max and Count. Also, it allows you to group the aggregation functions on one or more values. In our example, we will calculate a rating “A” or “F” based on the total amount of orders - if the total amount is higher than 50, it will be an “A”, otherwise “F”.

//Create rating for existing customers based total of order amount
Aggregation<Order, Rating> aggregation = new Aggregation<Order, Rating>();

It seems that some magic happened in the Aggregation. Let’s have a look at the CustomerRating object again:

public class Rating
    public int CustomerKey { get; set; }
    [AggregateColumn(nameof(Order.Amount), AggregationMethod.Sum)]
    public decimal TotalAmount { get; set; }

    public string RatingValue => TotalAmount > 50 ? "A" : "F";

The aggrgation gather it’s information from the attributes GroupColumn and AggregationColumn. The attribute [GroupColumn(nameof(Order.CustomerKey)] on the property CustomerKey tells the aggregation to the Orders by the CustomerKey and store the grouping value in the Rating result as well. The attribute [AggregateColumn(nameof(Order.Amount), AggregationMethod.Sum)] tells the aggregation to do a sum of Amount for each group.

The rating itself is then a simple getter method that checks if the sum of the amount is greater than 50 - if yes, the rating is “A”, else “F”.

Storing the customer rating

Now we want to store the calculated Rating in the table customer_rating. So we create another destination for this table and link it to our BlockTransformation.

//Store the rating in the customer rating table
DbDestination<Rating> destRating = new DbDestination<Rating>("customer_rating");

The table customer_rating has a column Rating. The attribute [DbColumnMap("Rating")] tells the DbDestination to store the data from the property RatingValue in the column Rating.

Starting the data flow

No we are all set to start the data flow. We can execute dataflow synchronously or asynchrounously. Thus, our csv source can to be started with either the Execute() or ExecuteAsync() methods.

In our example it looks like this:

//Execute the data flow synchronously

Checking the result

Now you can connect to your database and look into the tables customer_rating and orders. You will find in there the orders from the csv file, including a customer key as well as a customer rating based on the total amount of purchases.

Demo on Github

The whole demo code is available on GitHub   .