MySQL 存储过程说别名在 select 语句中未定义

Question

我有以下语句，它产生了这个错误。显然，select 语句第一行中的别名“R”没有声明，但它就在语句的末尾。有人有什么想法吗？

#1327 - 未声明的变量:R

    CREATE PROCEDURE `get_series_completion`(IN team1_id INT, IN team2_id INT, IN round_shortname VARCHAR(5))
BEGIN
    DECLARE num_games_total, num_games_played INT;

    SELECT COUNT(*) INTO num_games_played, R.games_per_series INTO num_games_total
    FROM (
        SELECT game_id
        FROM team_games
        WHERE team_id IN (team1_id, team2_id)
        GROUP BY game_id
            HAVING COUNT(*) = 2
            AND SUM(standing = 0) = 0
    ) AS S, rounds AS R ON R.round_shortname = round_shortname;

    SELECT num_games_played/num_games_total;
END$$

Answer 1

您应该在 into 子句之前选择所有列，您的查询应该是:

SELECT COUNT(*), R.games_per_series INTO num_games_played, num_games_total
    FROM (
        SELECT game_id
        FROM team_games
        WHERE team_id IN (team1_id, team2_id)
        GROUP BY game_id
            HAVING COUNT(*) = 2
            AND SUM(standing = 0) = 0
    ) AS S 
    LEFT OUTER JOIN rounds AS R ON R.round_shortname = round_shortname;

或

SELECT COUNT(*), R.games_per_series INTO num_games_played, num_games_total
    FROM (
        SELECT game_id
        FROM team_games
        WHERE team_id IN (team1_id, team2_id)
        GROUP BY game_id
            HAVING COUNT(*) = 2
            AND SUM(standing = 0) = 0
    ) AS S, rounds AS R 
    WHERE R.round_shortname(+) = round_shortname; -- implicit left outer join