oracle列转行函数 LISTAGG()

teacher_id	student_id	student_name
T001	S001	Amui
T002	S002	Lily
T003	S003	Lucy
T002	S004	Mark
T001	S005	Linda
T002	S006	Tom

                        t_people

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SELECT tp.teacher_id teacher_id,

            LISTAGG(tp.student_id,',') WITHIN GROUP (ORDER BY tp.student_id) AS student_ids

FROM  t_people tp

GROUP BY tp.teacher_id

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LISTAGG(tp.student_id,',') 中，第一个参数是所要由列转为行的值，第二个参数','表示用逗号分隔开该列的每个值。可以自定义该符号。

GROUP BY tp.teacher_id 表示：按teacher_id 对所要查找的列值进行分组。listagg() 函数就是将该语句所形成的分组中的每一组的值拼成字符串。

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结果如下：

teacher_id	student_ids
T001	S001,S005
T002	S002,S004,S006
T003	S003