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An example of using the array_agg() PostgreSQL function.
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| select | |
| pc_games.title, | |
| to_char(pc_games.release_date, 'YYYY-MM-DD') as release_date | |
| array_to_string(array_agg(avid_fans.firstname || ' ' || avid_fans.surname), ', ', null) as fans | |
| from | |
| schema_A.pc_games as pc_games | |
| inner join schema_A.avid_fans as avid_fans on (pc_games.id = avid_fans.fk_pc_game_id) | |
| where | |
| pc_games.release_date > '2004-12-31' | |
| group by | |
| pc_games.title, | |
| pc_games.release_date, | |
| avid_fans.firstname, | |
| avid_fans.surname | |
| -- Here we are selecting the particulars of all PC games released since 2016 along with all their fans. | |
| -- Because each PC game likely has more than one fan, we are going to see a lot of repeat data. | |
| -- Each record will contain the details of the PC game along with the name and surname of one fan. | |
| -- If a game has ten fans we are going to see the same game's details ten times folowed by each fan's name & surname. | |
| -- array_agg will place all the fans' names and surnames in a single field separated by commas. | |
| -- So instead of returning: | |
| ------------------------------------------------------------------------- | |
| -- title | release_date | fans -- | |
| ------------------------------------------------------------------------- | |
| -- Prince of Persia: The two thrones | 2005-06-15 | Pierre Joubert -- | |
| -- Prince of Persia: The two thrones | 2005-06-15 | Daniel France -- | |
| -- Prince of Persia: The two thrones | 2005-06-15 | Mariska Etsebeth -- | |
| ------------------------------------------------------------------------- | |
| -- The query will return: | |
| ---------------------------------------------------------------------------------------------------------- | |
| -- title | release_date | fans -- | |
| ---------------------------------------------------------------------------------------------------------- | |
| -- Prince of Persia: The two thrones | 2005-06-15 | Pierre Joubert, Daniel France, Mariska Etsebeth -- | |
| ---------------------------------------------------------------------------------------------------------- |
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