SOQL to return COUNT value via Apex

Question

I am trying to return the SOQL listed values into a field using an Apex Trigger:-

Object:

1. Name = RPA__c

Fields:

1. Business_Area__c (picklist) VALUES = Finland Managed Services, UK Managed Services
2. Business_ID_Number_HIDDEN__c (Number field) VALUES = integer

SOQL:

List<AggregateResult> lstResult =   [SELECT Business_Area__c value, Count(Id)  
                                    FROM Records_of_Processing_Activities__c 
                                    GROUP BY Business_Area__c];

So, the SOQL is returning as below:-

**Business Area                Count(id)**
Finland Managed Services       5
UK Managed Services            3

This is working perfectly and returns the correct count of the records where "Business Area" contains "Finland Managed Services" (3)

BUT

I am really struggling to capture that Count(id) and add it into a field in the RPA__c object (Business_ID_Number_HIDDEN__c is the field to apply the value into)

So:- I have written this so far, but is not returning the count(id) into the Business_Area__c field:-

trigger BATrigger on RPA__c (after insert, after update) 
{
    List<AggregateResult> lstResult =   [SELECT Business_Area__c value, Count(Id)  
                                        FROM RPA__c 
                                        GROUP BY Business_Area__c];
}
{
    List<Records_of_Processing_Activities__c> Business_ID_Number_HIDDEN__c = new List<Records_of_Processing_Activities__c>();
    for(AggregateResult result:lstResult);
}
    {
if (lstResult == 'Finland Managed Services') {
    Business_ID_Number_HIDDEN__c = Count(Id);
} else if (lstResult == 'UK Managed Services') {
    Business_ID_Number_HIDDEN__c = Count(Id);
} else {
    Business_ID_Number_HIDDEN__c = null;
}
    }
    update Business_ID_Number_HIDDEN__c; 
}

Any help or guidance would be greatly appreciated, again, very new to this so please be constructive in your appreciated help!

Answer 1

The default way to access espressions is expr0 for the first, expr1 for the second, and so on. A preferable way for most is to use an alias.

Adding an alias would work as below.

SELECT Business_Area__c, count(Id) recordCount
FROM MyObject__c WHERE ...

The actual retrieval of this attribute would work as below.

Without Alias

Integer count = result.get('expr0');

With Alias

Integer count = result.get('recordCount');