в 13:45, 26 мая 2010

2010-05-26T13:45:56Z

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2010-05-26T10:13:50Z

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==Concatenating strings==



<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"==



<source lang="sql">

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

</source>

==String Concatenation Operator Type Resolution==



<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==



<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>

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в 13:45, 26 мая 2010

Admin: 1 версия