As far as I get the question, there are no such structure as WHERE 1 in apex. Based on your question, next structure may be used:
List<String> and_conditions = new List<String>();
//add some condition like/
// and_conditions.add( ' test__c = true AND test_data__c != null ');
// and_conditions.add(' test__c = false AND test_data__c = \'Data\' ');
String where_clause = ' ';
if (!and_conditions.isEmpty()){
for(Integer i = 0; i < and_conditions.size(); i++){
if(i == 0){
where_clause = ' WHERE (' + and_conditions.get(i) + ') ';
}else{
where_clause +=' AND (' + and_conditions.get(i) + ') ';
}
}
}
That would support only AND clause as a root clause, but that is simple enough to understand pattern, and improve it on demand.
P.S. there are some statements which are always true. Like WHERE Id != null
P.S.S. With 1.5 year more experience, code written above can be improved
List<String> and_conditions = new List<String>();
//add some condition like/
// and_conditions.add( ' test__c = true AND test_data__c != null ');
// and_conditions.add(' test__c = false AND test_data__c = \'Data\' ');
String where_clause = ' ';
if (!and_conditions.isEmpty()){
where_clause = 'WHERE (' + String.join(and_conditions, ' ) AND ( ') + ')';
}