求一条SQL

Question

数据集：
column1   colum2
1           a
1           b
1           c
2           a
3           b
3           c
.           .
.           .
.           .结果：
column1        column2
1              a,b,c
2              a
3              b,c
.              .
.              .
.              .

Answer 1

select column1 ,wmsys.wm_concat(column2) from 表  group by column1