我认为MySQL中没有简单的方法。一种方法是通过为按rating_name分组的每一行生成一个行号，然后仅选择row_number为2或更少的行。在大多数数据库中，您可以使用以下方法进行此操作：
SELECt * FROM ( SELECt rating_name, etc..., ROW_NUMBER() OVER (PARTITION BY rating_name ORDER BY good) AS rn FROM your_table) T1WHERe rn <= 2
不幸的是，MySQL不支持该
ROW_NUMBER语法。但是，您可以
ROW_NUMBER使用变量进行模拟：
SELECt rating_name, id_markets, good, neutral, badFROM ( SELECt *, @rn := CASE WHEN @prev_rating_name = rating_name THEN @rn + 1 ELSE 1 END AS rn, @prev_rating_name := rating_name FROM ( SELECt rating_name, id_markets, SUM(COALESCE(rating_good, 0)) AS good, SUM(COALESCE(rating_neutral, 0)) AS neutral, SUM(COALESCE(rating_bad, 0)) AS bad FROM zzratings WHERe rating_year = YEAR(CURDATE()) AND rating_week = WEEK(CURDATE(), 1) GROUP BY rating_name, id_markets ) AS T1, (SELECT @prev_rating_name := '', @rn := 0) AS vars ORDER BY rating_name, good DESC) AS T2WHERe rn <= 2ORDER BY rating_name, good DESC
对测试数据运行时的结果：
法国1 2 0 0法国2 1 0 0爱尔兰1 4 2 0爱尔兰21 3 1 0波兰1 3 1 0波兰2 1 0 0
