Просмотр исходного текста страницы PostgreSQL/Postgre SQL/String Concatenate

==Concatenating strings==



   
  <!-- start source code -->
   
    <source lang="sql">

postgres=#
postgres=#
postgres=#
postgres=# CREATE TABLE employee (
postgres(#     ID         int,
postgres(#     name       varchar(10),
postgres(#     salary     real,
postgres(#     start_date date,
postgres(#     city       varchar(10),
postgres(#     region     char(1)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (1,  "Jason", 40420,  "02/01/94", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (4,  "Linda", 40620,  "11/04/97", "New York", "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (5,  "David", 80026,  "10/05/98", "Vancouver","W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (7,  "Alison",90620,  "08/07/00", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W");
INSERT 0 1
postgres=#
postgres=# select * from employee;
 id |  name  | salary | start_date |   city    | region
----+--------+--------+------------+-----------+--------
  1 | Jason  |  40420 | 1994-02-01 | New York  | W
  2 | Robert |  14420 | 1995-01-02 | Vancouver | N
  3 | Celia  |  24020 | 1996-12-03 | Toronto   | W
  4 | Linda  |  40620 | 1997-11-04 | New York  | N
  5 | David  |  80026 | 1998-10-05 | Vancouver | W
  6 | James  |  70060 | 1999-09-06 | Toronto   | N
  7 | Alison |  90620 | 2000-08-07 | New York  | W
  8 | Chris  |  26020 | 2001-07-08 | Vancouver | N
  9 | Mary   |  60020 | 2002-06-09 | Toronto   | W
(9 rows)
postgres=#
postgres=# --Concatenating strings
postgres=#
postgres=# SELECT "The Name: " || name AS name_info FROM employee;
    name_info
------------------
 The Name: Jason
 The Name: Robert
 The Name: Celia
 The Name: Linda
 The Name: David
 The Name: James
 The Name: Alison
 The Name: Chris
 The Name: Mary
(9 rows)
postgres=#
postgres=#
postgres=# drop table employee;
DROP TABLE
postgres=#
           
       </source>
    
   


==SELECT "abc" || "def"==



   
  <!-- start source code -->
   
    <source lang="sql">

postgres=#
postgres=# SELECT "abc" || "def" AS "unspecified";
 unspecified
-------------
 abcdef
(1 row)
postgres=#
           
       </source>
    
   


==String Concatenation Operator Type Resolution==



   
  <!-- start source code -->
   
    <source lang="sql">

postgres=# -- String Concatenation Operator Type Resolution
postgres=#
postgres=# SELECT text "abc" || "def" AS "text and unknown";
 text and unknown
------------------
 abcdef
(1 row)
postgres=#
postgres=#
           
       </source>
    
   


==Using operators with NULL values==



   
  <!-- start source code -->
   
    <source lang="sql">

postgres=#
postgres=# -- Using operators with NULL values
postgres=#
postgres=# \pset null *null* Null display is "*null*".
Null display is "*null*".
\pset: extra argument "Null" ignored
\pset: extra argument "display" ignored
\pset: extra argument "is" ignored
\pset: extra argument "*null*" ignored
\pset: extra argument "." ignored
postgres=#
postgres=# SELECT 5 > NULL;
 ?column?
----------
 *null*
(1 row)
postgres=#
postgres=# SELECT NULL IS NULL;
 ?column?
----------
 t
(1 row)
postgres=#
postgres=# SELECT NULL || "Test";
 ?column?
----------
 *null*
(1 row)
postgres=#
postgres=#
           
       </source>