MySQL内部连接别名问题

Question

I am trying to write an sql join but I'm getting a not unique error:

SELECT matches.match_id, 
       teamsh.team_name  AS "homeTeam", 
       teamsh.team_id    AS "homeID", 
       teamsa.team_name  AS "awayTeam", 
       teamsa.team_id    AS "awayID", 
       competition.NAME, 
       competition.competition_id, 
       teamsh.stadium, 
       matches.date, 
       teamsh.name_short AS "homeTeamShort", 
       teamsa.name_short AS "awayTeamShort", 
       teamsh.pysioid    AS "pysioIDh", 
       teamsa.pysioid    AS "pysioIDa" 
FROM   matches, 
       teams teamsh, 
       teams teamsa, 
       competition

INNER JOIN
teamsh ON matches.home_team_id = teamh.team_id,
teamsa ON matches.away_team_id = teama.team_id,
competition ON matches.competition_id = competition.competition_id ​

WHERE  match_id = 22268 

1066 - Not unique table/alias: 'teamsh'.

I know i'm close but the alias has beaten me.

Thank you in advance,

Al.

Answer 1

You're mixing old-style joins with proper join syntax:

SELECT matches.match_id, 
       teamsh.team_name  AS "homeTeam", 
       teamsh.team_id    AS "homeID", 
       teamsa.team_name  AS "awayTeam", 
       teamsa.team_id    AS "awayID", 
       competition.NAME, 
       competition.competition_id, 
       teamsh.stadium, 
       matches.date, 
       teamsh.name_short AS "homeTeamShort", 
       teamsa.name_short AS "awayTeamShort", 
       teamsh.pysioid    AS "pysioIDh", 
       teamsa.pysioid    AS "pysioIDa" 
FROM   matches
INNER JOIN
teams AS teamsh ON matches.home_team_id = teamsh.team_id
INNER JOIN 
teams AS teamsa ON matches.away_team_id = teamsa.team_id
INNER JOIN
competition ON matches.competition_id = competition.competition_id ​
WHERE  match_id = 22268 

You were getting the error because teamsh and teamsa were used multiple times as table names/aliases.

Answer 2

The problem is in your FROM clause. It should look like this:

FROM  matches
INNER JOIN
teams teamsh ON matches.home_team_id = teamh.team_id
INNER JOIN
teams teamsa ON matches.away_team_id = teama.team_id
INNER JOIN
competition ON matches.competition_id = competition.competition_id ​