4.4QUERY

This is probably the Salesforce operation you'll use most besides Upsert.

Imagine:

GET /customers/CUST-123

Mule needs to find the corresponding Salesforce Account.

Flow:

HTTP Listener
      ↓
Salesforce Query
      ↓
Transform response

SOQL:

SELECT
    Id,
    Name,
    Phone,
    BillingCity,
    BillingState
FROM Account
WHERE External_Customer_ID__c = :customerId

The connector's Query operation accepts SOQL and supports parameters.

Conceptually:

query:
SELECT Id, Name
FROM Account
WHERE External_Customer_ID__c = :customerId

parameters:
{
    customerId: vars.customerId
}

This is preferable to dynamically constructing:

"... WHERE External_Customer_ID__c = '"
    ++ vars.customerId
    ++ "'"

for exactly the reasons you'd expect from other database/API development:

safer
cleaner
escaping handled correctly
easier to maintain