QBCaseWhen

var query = datasources.db.example_data.order_details.createSelect();

// case expressions can be added to the result of the query
	query.result.add(query.case.when(query.columns.quantity.ge(1000)).then('BIG').else('small'));

 // they can also be used in conditions
	query.where.add(query.case
		.when(query.columns.discount.gt(10)).then(50)
		.when(query.columns.quantity.le(20)).then(70)
		.else(100)
	.multiply(query.columns.unitprice).lt(10000));