concat_ws(分隔符,字段1,字段2)
string_agg(‘字符串’,‘分隔符’)

  select string_agg(concat_ws(',',a,b),',') from test_table

参考案例：

(postgres@[local]) [sbtest] 17:18:32# create table t1 (c1 int, c2 int);
CREATE TABLE
Time: 5.341 ms
(postgres@[local]) [sbtest] 17:18:37# insert into t1 values (1,1),(2,2),(3,3);
INSERT 0 3
Time: 2.968 ms
(postgres@[local]) [sbtest] 17:18:37# select row(t1.c1, t1.c2) as new_col from t1;
+---------+
| new_col |
+---------+
| (1,1)   |
| (2,2)   |
| (3,3)   |
+---------+
(3 rows)