OLAP and OLTP In Query Complexity

Hello Everyone, I want to know which one is more query complex between OLAP and OLTP. As i know both OLAP and OLTP systems are query-based. However, queries concerning the OLTP systems are simple as compared to OLAP systems that provide support for complex queries, This according to OLTP vs OLAP post but Is it true OLAP is more complex to OLTP? Can anyone know about it?