Apex Variables in SOQL Queries

Bind expressions are used in the WHERE clause to compare the field’s value with an Apex variable. It uses the following syntax:

WHERE field_name comparisionOperator :bind_variable

Consider this Apex snippet:

String clinicName = 'Orlando';
List<Appointment__c> appointmentList = [SELECT Id, Patient__r.Name
FROM Appointment__c
WHERE Clinic__r.name = :clinicName];

In this example, the name of the clinic is compared with a variable clinicName. You will find it extremely helpful if the code was in an apex method where values were passed as variables.

Example: Design an apex method that returns the maximum number of appointments it can handle in a day given the clinic’s name.

public Integer geMaxNoOfAppointments(String clinicName){
  List<Clinic__c> clinicList = [SELECT Id, Name, max_no_of_appointments__c  
  FROM Clinic__c
  WHERE name= :clinicName];
  return clinicList [0].max_no_of_appointments__c ;