Question

I have these tables :
TBL_PERSONS – a table for persons
TBL_SPORTS – a table for sports like football , basketball , tennis and …
TBL_PERSON_SPORT – a table for any person’s sports

for example Jo can play Football , and Basketball
I want to create a VIEW on persons and their sports.
something like this:

Jo|Football,Basketball
Jack|Football,Tennis

how should I write such VIEW?
thanks.

Answer 1

If you really want them to be a comma-separated list, that is the function of the GROUP_CONCAT() aggregate function. Substitute the correct names of your columns in place of name, person_id, sport_id, etc…

CREATE VIEW PERSON_SPORTS AS
(
SELECT
  p.name,
  GROUP_CONCAT(s.sport_name) AS sports
FROM
  TBL_PERSONS p
  LEFT JOIN TBL_PERSON_SPORT sp ON p.person_id = sp.person_id
  JOIN TBL_SPORTS s ON sp.sport_id = s.sport_id
GROUP BY p.name
);

The above won’t be very useful for joining against though, if you need to be able to separate out sports from the comma-separated list. Consider also just wrapping the ungrouped list in a view as:

CREATE VIEW PERSON_SPORTS AS
(
SELECT
  DISTINCT
  p.name,
  s.sport_name AS sport
FROM
  TBL_PERSONS p
  LEFT JOIN TBL_PERSON_SPORT sp ON p.person_id = sp.person_id
  JOIN TBL_SPORTS s ON sp.sport_id = s.sport_id
);

This will produce one row per sport, containing the person’s name and sport name, where the person is duplicated as many times as needed for each sport.