Salesforce Salesforce Object Query Language (SOQL) Variable References in Apex SOQL Queries
Example
To reference a variable in a query, add a colon (:) before the variable name.
Datetime targetDate = Datetime.now().addDays(-7);
List<Lead> recentLeads = [SELECT Id FROM Lead WHERE CreatedDate > :targetDate];
string targetName = 'Unknown';
List<Contact> incompleteContacts = [SELECT Id FROM Contact WHERE FirstName = :targetName];
