row

oldRow

Insert (audit) changes for the current entity.
Call an external resource.
For example, you can have your event rule determine the lat/long coordinates to be used in a Google map for product delivery. You do this using an event rule that passes a customer's address to a resource which in turn calls Google Geocode.
Send email.
Update a calendar system.
Post a message on a queue.
Call a push notification engine.

Event.
 Fires after row-logic is completed. The row data reflects derivation results.
You can change the row within the code of an event rule, but you must ensure that required logic is executed using the 
logicContext.save()
 method.
Early event.
 Fires before your logic executes. The row data is not subjected to formulas and other derivations. You can change the row and the changes are subjected to validations, other chained logic, and saved.
Commit Event.
Fires after row-logic is completed for all the rows in the transaction. The rows reflect logic processing. You cannot change the rows.
Pre-Insert event.
 Fires before sending the row to the database on insert. You can use pre-insert event to generate the primary key or compute a non-nullable attribute before inserting a row to the table. 

Define Order event MaintainCount as
if (logicContext.initialVerb == 'INSERT' && row.isPaid == false) { // row is the order
    customer = row.customer; // parent accessor
    customer.balance += row.amountTotal;
    logicContext.update(customer);
}

Delete order: Decrement the count only if the order
isPaid
.
Change
Order.isPaid
: Watch for such a change, and if you detect it, adjust the sum by amountTotal.
Change
Order.amountTotal
: Watch for such a change, and if you detect it, adjust the sum by the difference.
Reassign order: Often overlooked, reduce the previous customers'
balance
, increase the new one, only if the order
isPaid
.

Cell A =
  Sum(ColumnB)

Customer.balance = 
  sum(orders.amountTotal where paid = false)

 In the Manage section, click 
Rules
.
If your API does not have existing rules, the Welcome to Rules page appears. If your API has existing rules, they are listed on the By entity tab by default.
Click 
Create a Rule
.
Do the following:
Specify when the event is fired by selecting one of the following event rule types:
Event
Early Event
Commit Event
Preinsert Event
If you want to change primary keys within an event, select
Early Event
,
Commit Event
, or
Preinsert Event
.
Select the entity to which the rule applies.
Click 
Create Rule
.
Define the parameters of the rule, and then click
Activate and Close
:
Title
The title for the event rule. The title for rules does not affect logic processing. To apply a default value, leave this field blank.
Required:
 No
Entity
The name of the entity being acted upon.
Topics
The topic that you want to associate to this rule.
For more information about topics, see Manage Topics.
Code
The code for your event rule. You can access and insert JavaScript code examples into the code editor.
For more information about the code examples that are available for event rules, see Code Examples.
You can have 
CA Live API Creator
 return an object and assign it to a row attribute. This object represents the current date, time, or timestamp on the database server at the instant the resulting SQL is executed on the database server. You can do this by way of the 
SysUtility
 JavaScript object's 
databaseNowDeferred()
 method or the 
sqlSnippetDeferred()
 method.
For more information about these methods, see The SysUtility Object.
Example:
 A typical example is an auditing event. The use of the current/old bean in making your logic conditional:
 
if (row.amount_total != oldRow.amount_total) 
  SysLogic.insertChildFrom("purchaseorder_audit", logicContext);
 
Active
Select to activate the rule.
Default:
 Cleared
The API must be complete.
Asynchronous
Select this checkbox to have 
CA Live API Creator
 execute the event rule asynchronously, independent of the current transaction. The execution of the event does not affect the current transaction. Running your request event asynchronously can be helpful for processes that might take a long time, such as making an external call or sending an email.
Name
The name of the event rule. Leave this field blank for the system default.