Postgresql has a lot of built-in practical functions. Here are the combination and cutting functions
Environment: PostgreSQL 9.1.2
          CENTOS 5.7 final 

1, Combined function
1.concat 
a. Grammar introduction

concat(str "any" [, str "any" [, ...]])

Concatenate all but first arguments with separators.
The first parameter is used as a separator. 
NULL arguments are ignored.

b. Practical example:

postgres=# create table t_kenyon(id int,name varchar(10),remark text);
CREATE TABLE
postgres=# insert into t_kenyon values(1,'test','kenyon'),(2,'just','china'),(3,'iam','lovingU');
INSERT 0 3
postgres=# insert into t_kenyon values(4,'test',null);
INSERT 0 1
postgres=# insert into t_kenyon values(5,null,'adele');
INSERT 0 1
postgres=# select * from t_kenyon;
 id | name | remark  
----+------+---------
  1 | test | kenyon
  2 | just | china
  3 | iam  | lovingU
  4 | test | 
  5 |      | adele
(5 rows)

postgres=# select concat(id,name,remark) from t_kenyon;
   concat    
-------------
 1testkenyon
 2justchina
 3iamlovingU
 4test
 5adele
(5 rows)

c. description
Concat function is a splicing function. null value splicing can be ignored. The splicing value has no separator. If the separator is needed, the following function concat? WS is needed.  

2.concat_ws 
a. Grammar introduction

concat_ws(sep text, str "any" [, str "any" [,...] ])

Concatenate all but first arguments with separators.
The first parameter is used as a separator.
NULL arguments are ignored.

b. Practical application

postgres=# select concat_ws(',',id,name,remark) from t_kenyon;
   concat_ws   
---------------
 1,test,kenyon
 2,just,china
 3,iam,lovingU
 4,test
 5,adele
(5 rows)

postgres=# select concat_ws('_',id,name,remark) from t_kenyon;
   concat_ws   
---------------
 1_test_kenyon
 2_just_china
 3_iam_lovingU
 4_test
 5_adele
(5 rows)

postgres=# select concat_ws('',id,name,remark) from t_kenyon;
  concat_ws  
-------------
 1testkenyon
 2justchina
 3iamlovingU
 4test
 5adele
(5 rows)

postgres=# select concat_ws('^_*',id,name,remark) from t_kenyon;
     concat_ws     
-------------------
 1^_*test^_*kenyon
 2^_*just^_*china
 3^_*iam^_*lovingU
 4^_*test
 5^_*adele
(5 rows)

c. It shows that concat? WS function has more separator functions than concat function. In fact, it is the upgraded version of concat. If the separator is' ', the result is the same as concat. Concat | WS separators also support multiple characters as separators, which may be used more frequently in daily life.   

2, Cut function
1.split_part 
a. Grammar introduction

split_part(string text, delimiter text, field int)

Split string on delimiter and return the given field (counting from one)

b. Practical examples

postgres=# select split_part('abc~@~def~@~ghi','~@~', 2);
 split_part 
------------
 def
(1 row)

postgres=# select split_part('now|year|month','|',3);
 split_part 
------------
 month
(1 row)

c. description
This function is very effective for taking the value of a specific location by separator

2.regexp_split_to_table 
a. Grammar introduction

regexp_split_to_table(string text, pattern text [, flags text])

Split string using a POSIX regular expression as the delimiter.

b. Examples of use

postgres=# SELECT regexp_split_to_table('kenyon,love,,china,!',',');
 regexp_split_to_table 
-----------------------
 kenyon
 love
 
 china
 !
(5 rows)

--Cut by divider
postgres=# SELECT regexp_split_to_table('kenyon, china loves',E'\\s');
 regexp_split_to_table 
-----------------------
 kenyon,
 china
 loves
(3 rows)

--Cut by letter
postgres=# SELECT regexp_split_to_table('kenyon,,china',E'\\s*');
 regexp_split_to_table 
-----------------------
 k
 e
 n
 y
 o
 n
 ,
 ,
 c
 h
 i
 n
 a
(13 rows)

3.regexp_split_to_array 
a. Grammar introduction

regexp_split_to_array(string text, pattern text [, flags text ])

Split string using a POSIX regular expression as the delimiter.

b. Practical examples

postgres=# SELECT regexp_split_to_array('kenyon,love,,china,!',',');
  regexp_split_to_array   
--------------------------
 {kenyon,love,"",china,!}
(1 row)

postgres=# SELECT regexp_split_to_array('kenyon,love,,china!','s*');
             regexp_split_to_array             
-----------------------------------------------
 {k,e,n,y,o,n,",",l,o,v,e,",",",",c,h,i,n,a,!}
(1 row)

c. description

S * in the flag used above means split all, and E'\s' means escape space

From: https://my.oschina.net/Kenyon/blog/76819