[yk_0427@kwemhisprc01300 ~]$ cat /etc/system-release
CentOS Linux release 7.6.1810 (Core)
[yk_0427@kwemhisprc01300 ~]$ uname -a
Linux kwemhisprc01300 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

1、创建表插入数据
create table t_orafce_41 (id int,content text);
insert into t_orafce_41 values(1,'testtext1');
insert into t_orafce_41 values(1,'testtext2');
insert into t_orafce_41 values(2,'testtext3');
insert into t_orafce_41 values(2,'testtext4');
insert into t_orafce_41 values(3,'testtext5');
insert into t_orafce_41 values(3,'testtext6');
2、使用wm_concat函数拼接列值
select wm_concat(content::text) from t_orafce_41;
select wm_concat(content::text) from t_orafce_41 group by id;
select id,wm_concat(content::text) from t_orafce_41 group by id;

yk_0427@postgres=#select wm_concat(content::text) from t_orafce_41;
ERROR:  function wm_concat(text) does not exist
LINE 1: select wm_concat(content::text) from t_orafce_41;
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
CONTEXT:  referenced column: wm_concat
yk_0427@postgres=#select wm_concat(content::text) from t_orafce_41 group by id;
ERROR:  function wm_concat(text) does not exist
LINE 1: select wm_concat(content::text) from t_orafce_41 group by id...
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
CONTEXT:  referenced column: wm_concat
yk_0427@postgres=#select id,wm_concat(content::text) from t_orafce_41 group by id;
ERROR:  function wm_concat(text) does not exist
LINE 1: select id,wm_concat(content::text) from t_orafce_41 group by...
                  ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
CONTEXT:  referenced column: wm_concat
yk_0427@postgres=#