Data Controllers / Fields

  SQL Formula

Data Controllers / FieldsPrint||
SQL Formula

Let’s examine two tables in the Northwind database, Employees and Orders. Each order is linked to an employee via the EmployeeID foreign key relationship.

Employees and Orders table diagram from the Northwind database

A Code On Time web application will perform automatic denormalization and use the LastName field as alias for EmployeeID. This field is shown below, labeled “Employee Last Name”.

Default Orders edit form with 'Employee Last Name' field

The end user may want to see the full name of the employee instead.

Let’s create a calculated field that combines First Name and Last Name of the employee, and use this field as an alias for EmployeeID in both Employees and Orders controllers.

Creating the Calculated Field in Employees Controller

Activate the Project Designer. In the Explorer, switch to Controllers tab. Let’s take a look at the command of Employees controller. Double-click on Employees / Commands / command1 node.

Employees 'command1' in Code On Time Project Explorer

Take a look at the text of the command.

select
    "Employees"."EmployeeID" "EmployeeID"
    ,"Employees"."LastName" "LastName"
    ,"Employees"."FirstName" "FirstName"
    ,"Employees"."Title" "Title"
    ,"Employees"."TitleOfCourtesy" "TitleOfCourtesy"
    ,"Employees"."BirthDate" "BirthDate"
    ,"Employees"."HireDate" "HireDate"
    ,"Employees"."Address" "Address"
    ,"Employees"."City" "City"
    ,"Employees"."Region" "Region"
    ,"Employees"."PostalCode" "PostalCode"
    ,"Employees"."Country" "Country"
    ,"Employees"."HomePhone" "HomePhone"
    ,"Employees"."Extension" "Extension"
    ,"Employees"."Photo" "Photo"
    ,"Employees"."Notes" "Notes"
    ,"Employees"."ReportsTo" "ReportsTo"
    ,"ReportsTo"."LastName" "ReportsToLastName"
    ,"Employees"."PhotoPath" "PhotoPath"
from "dbo"."Employees" "Employees"
    left join "dbo"."Employees" "ReportsTo" on "Employees"."ReportsTo" = "ReportsTo"."EmployeeID"

You can see the alias “Employees” in front of the LastName and FirstName columns. You will need to use this alias when referring to columns of the Employees table in the SQL Formula of the calculated field.

Make sure not to modify and/or save the command – the code generator
will stop automatically updating the command if you do so.

Let’s create the new field. Right-click on Employees / Fields node and select New Field option.

New Field for Employees data controller

Give this field the following settings:

Property Value
Name EmployeeFullName
Allow Null Values True
The value of this field is computed at run-time by SQL expression.
"Employees"."LastName" + ', ' + "Employees"."FirstName"
Label Employee Full Name
Values of this field cannot be edited True
Allow Query-by-Example True
Allow Sorting True

Press OK to save the new field.

Now let’s change the data fields in the grid view. In the Project Explorer, double-click on Employees / Views / grid1 / LastName data field node.

'LastName' data field in grid1 view of Employees controller

Make the following change:

Property New Value
Field Name EmployeeFullName

Press OK to save the data field. In the Project Explorer, right-click on Employees / Views / grid1 / FirstName data field node, and choose Delete option. Select OK to confirm the delete operation.

Delete 'FirstName' data field from 'grid1' view of Employees data controller

Creating the Calculated Field in Orders Controller

Before creating the “EmployeeFullName” field in Orders controller, we’ll need to find the alias of the Employees tables in the command text.

Double-click on Orders / Commands / command1 node.

Orders 'command1' in Code On Time Project Explorer

Take a look at the text of the command.

select
    "Orders"."OrderID" "OrderID"
    ,"Orders"."CustomerID" "CustomerID"
    ,"Customer"."CompanyName" "CustomerCompanyName"
    ,"Orders"."EmployeeID" "EmployeeID"
    ,"Employee"."LastName" "EmployeeLastName"
    ,"Orders"."OrderDate" "OrderDate"
    ,"Orders"."RequiredDate" "RequiredDate"
    ,"Orders"."ShippedDate" "ShippedDate"
    ,"Orders"."ShipVia" "ShipVia"
    ,"ShipVia"."CompanyName" "ShipViaCompanyName"
    ,"Orders"."Freight" "Freight"
    ,"Orders"."ShipName" "ShipName"
    ,"Orders"."ShipAddress" "ShipAddress"
    ,"Orders"."ShipCity" "ShipCity"
    ,"Orders"."ShipRegion" "ShipRegion"
    ,"Orders"."ShipPostalCode" "ShipPostalCode"
    ,"Orders"."ShipCountry" "ShipCountry"
from "dbo"."Orders" "Orders"
    left join "dbo"."Customers" "Customer" on "Orders"."CustomerID" = "Customer"."CustomerID"
    left join "dbo"."Employees" "Employee" on "Orders"."EmployeeID" = "Employee"."EmployeeID"
    left join "dbo"."Shippers" "ShipVia" on "Orders"."ShipVia" = "ShipVia"."ShipperID"

You can see that this data controller refers to Employees using “Employee”, which is different than the Employees data controller reference of “Employees”. The SQL Formula of the calculated field will need to use the alias of the command text in Orders data controller.

Make sure not to save any changes to the command. Right-click on Orders / Fields node, and choose New Field.

New Field in Orders data controller

Use the following settings for the new field:

Property Value
Name EmployeeFullName
Allow null values True
The value of this field is computed at run-time by SQL Expression
"Employee"."LastName" + ', ' + "Employee"."FirstName"
Label Employee Full Name
Values of this field cannot be edited True
Allow Query-by-Example True
Allow Sorting True

Press OK to save the field.

Let’s change the alias of the EmployeeID data fields in each view so that Employee Full Name is displayed. In the Explorer, double-click on Orders / Fields / EmployeeID field node.

EmployeeID field of Orders data controller

At the top, switch to Data Fields tab. For all three data fields, make the following change:

Property New Value
Alias EmployeeFullName

Change Alias to 'EmployeeFullName' for all EmployeeID data fields

On the tool bar, press Browse to generate the web application. When it opens in your default web browser, navigate to Orders page. The EmployeeID field now shows the full name of each employee, instead of just the last name.

Employee Full Name displayed for Orders data view

If you edit a record and activate the lookup for Employee Full Name, you will see that the grid view will show the Employee Full Name in the first column.

Employee Full Name displayed in EmployeeID lookup

Selecting a record from the grid will insert the full name into the lookup field.

Employee Full Name inserted into EmployeeID lookup field

Navigate to the Employees page of the web application. If you activate inline edit mode on the grid view, you will not be able to edit the Employee Full Name field.

Employee Full Name is read-only in grid view

However, if you edit a record using form view, the original First Name and Last Name fields are still there.

Last Name and First Name fields are editable in edit form

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