oracle - SQL JOIN and LEFT OUTER JOIN -

oracle - SQL JOIN and LEFT OUTER JOIN -

i've been having problem understanding example, have reply i'm having problem wrapping head around how works. how joins working exactly?

examine structures of player , team tables:

player ------------- player_id number(9) pk last_name varchar2(25) first_name varchar2(25) team_id number manager_id number(9) team ---------- team_id number pk team_name varchar2(30)

for example, team managers players, , manager_id column references player_id column. players managers, manager_id null.

which select statement provide list of players, including player's name, team name, , player's manager's name?

answer:

select p.last_name, p.first_name, m.last_name, m.first_name, t.team_name player p left outer bring together player m on (p.manager_id = m.player_id) left outer bring together team t on (p.team_id = t.team_id);

so first left outer join takes player table, adds on info each players manager. each player has id manager, player id. if mr. a, player_id 9, manager ted, player_id 5, ted's manager_id 9. first bring together takes ted's manager_id, 9, , matches player_id of manager, mr. a, manager's info on table well, , m.last_name , m.first_name show mr. a's name. sec bring together takes team_id , matches table of teams, appending team_name player's info in table.

it's tough explain without sample info , diagrams. sorry.

sql oracle join outer-join