pentabarf_pgcon=# SELECT DISTINCT E.title, string_agg(S.name,', ') as name, E.event_type
  FROM event E, view_event_person P, view_mail_all_speaker S
 WHERE E.event_id = P.event_id
   AND P.person_id = S.person_id
   AND E.conference_id = 12
   and E.event_state = 'accepted'
   and P.event_role_name = 'Speaker'
  group by E.title, E.event_type order by 2;
                                title                                 |               name               | event_type 
----------------------------------------------------------------------+----------------------------------+------------
 PostgreSQL extendability: Origins and new horizonts                  | Alexander Korotkov               | lecture
 Faster PostgreSQL: Improved Writes                                   | Amit Kapila                      | lecture
 B-Tree - explore the heart of PostgreSQL.                            | Anastasia Lubennikova            | lecture
 PostgreSQL's buffer manager - Problems & Improvements                | Andres Freund                    | lecture
 Data interoperability using PostgreSQL Foreign Data Wrapper          | Ariel Guerra                     | lecture
 Foreign Data Wrappers - how to write them and use them.              | Ashutosh Bapat, Rushabh Lathia   | tutorial
 PostgreSQL When It is Not Your Job                                   | Christophe Pettus                | tutorial
 The PCI Compliant Database.                                          | Christophe Pettus                | lecture
 Run Simple Query Faster                                              | Dilip Kumar                      | lecture
 Experience Cuba with PostgreSQL: PostgreSQL Diploma                  | Gilberto Castillo                | lecture
 In-memory column store                                               | Hari Babu                        | lecture
 Index Internals                                                      | Heikki Linnakangas               | lecture
 Autovacuum, explained for engineers                                  | Ilya Kosmodemiansky              | lecture
 Benchmarking Databases                                               | Jan Wieck                        | lecture
 MLS PostgreSQL                                                       | Joe Conway                       | lecture
 Managing OS Provided PostgreSQL Packages                             | Keith Fiske                      | lecture
 ERROR: snapshot too old                                              | Kevin Grittner                   | lecture
 Building a BaaS using PostgreSQL                                     | Lakshmi Narasimhan Parthasarathy | lecture
 pg_paxos: Paxos-based table replication                              | Marco Slot                       | lecture
 Unveiling pg_global_kv                                               | Matthew Kelly                    | lecture
 Not Easy Being Green                                                 | Noah Misch                       | lecture
 FTS is dead ? Long live FTS !                                        | Oleg Bartunov, Teodor Sigaev     | lecture
 Lessons in Building a Distributed Query Planner                      | Ozgun Erdogan                    | lecture
 Overlooked Data Types                                                | Peter van Hardenberg             | lecture
 WAL Reduction                                                        | Rahila Syed                      | lecture
 Parallel Query Has Arrived!                                          | Robert Haas                      | lecture
 PoWA 3: towards a computer assisted DBA                              | Ronan Dunklau                    | lecture
 9.4 The Hard Way                                                     | Samantha Billington              | lecture
 PostgreSQL High-Availability and Geographic Locality using consul... | Sean Chittenden                  | lecture
 Setting up Vault for HA PKI and Secrets management...                | Sean Chittenden                  | tutorial
 Non-volatile Memory Logging                                          | Takashi Horikawa                 | lecture
 A Challenge of Huge Billing System Migration                         | Tatsuro Yamada                   | lecture
 Queues in PostgreSQL                                                 | Thomas Munro                     | lecture
 Yandex.Mail success story                                            | Vladimir Borodin                 | lecture
 Beyond EXPLAIN: Query Optimization From Theory To Code               | Yuto Hayamizu, Ryoji Kawamichi   | lecture
 Hands-On Lab: New PostgreSQL 9.5 features                            | Álvaro Hernández Tortosa         | tutorial
(36 rows)

pentabarf_pgcon=#