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group_concat([DISTINCT] 要连接的字段 [Order BY ASC/DESC 排序字段] [Separator '分隔符'])

SELECT id,GROUP_CONCAT(score) FROM testgroup GROUP BY id;
SELECT id,GROUP_CONCAT(DISTINCT score) FROM testgroup GROUP BY id;
SELECT id,GROUP_CONCAT(score ORDER BY score DESC) FROM testgroup GROUP BY id;
SELECT id,GROUP_CONCAT(score SEPARATOR ';') FROM testgroup GROUP BY id;