Perl連線PostgreSQL資料庫

PostgreSQL可以使用Perl DBI模組與Perl整合，Perl DBI模組是Perl程式設計語言的資料庫存取模組。 它定義了一組提供標準資料庫介面的方法，變數和約定。

以下是在Linux / Unix機器上安裝DBI模組的簡單步驟：

$ wget http://search.cpan.org/CPAN/authors/id/T/TI/TIMB/DBI-1.625.tar.gz
$ tar xvfz DBI-1.625.tar.gz
$ cd DBI-1.625
$ perl Makefile.PL
$ make
$ make install

如果您需要安裝DBI的SQLite驅動程式，那麼可以安裝如下：

$ wget http://search.cpan.org/CPAN/authors/id/T/TU/TURNSTEP/DBD-Pg-2.19.3.tar.gz
$ tar xvfz DBD-Pg-2.19.3.tar.gz
$ cd DBD-Pg-2.19.3
$ perl Makefile.PL
$ make
$ make install

在開始使用Perl連線PostgreSQL介面之前，請在PostgreSQL安裝目錄中找到pg_hba.conf檔案，並新增以下行：

# IPv4 local connections:
host    all         all         127.0.0.1/32          md5

您可以啟動/重新啟動postgres伺服器，可使用以下命令執行：

[root@host]# service postgresql restart
Stopping postgresql service:                               [  OK  ]
Starting postgresql service:                               [  OK  ]

Perl連線到PostgreSQL資料庫

以下Perl程式碼顯示如何連線到現有的資料庫。 如果資料庫不存在，那麼它將自動建立，最後將返回一個資料庫物件。

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "Pg"; 
my $database = "testdb";
my $dsn = "DBI:$driver:dbname=$database;host=127.0.0.1;port=5432";
my $userid = "postgres";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 }) 
                      or die $DBI::errstr;

print "Opened database successfully\n";

現在，我們執行上面的程式來開啟資料庫:testdb，如果成功開啟資料庫，那麼它將給出以下訊息：

Open database successfully

建立表

以下Perl程式將用於在之前建立的資料庫(testdb)中建立一個表：

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "Pg"; 
my $database = "testdb";
my $dsn = "DBI:$driver:dbname=$database;host=127.0.0.1;port=5432";
my $userid = "postgres";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(CREATE TABLE COMPANY
      (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL););
my $rv = $dbh->do($stmt);
if($rv < 0){
   print $DBI::errstr;
} else {
   print "Table created successfully\n";
}
$dbh->disconnect();

當執行上述程式時，它將在testdb中建立一張COMPANY表，並顯示以下訊息：

Opened database successfully
Table created successfully

插入操作

以下Perl程式顯示了如何在上述範例中建立的COMPANY表中建立/插入記錄：

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "Pg"; 
my $database = "testdb";
my $dsn = "DBI:$driver:dbname=$database;host=127.0.0.1;port=5432";
my $userid = "postgres";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (1, 'Paul', 32, 'California', 20000.00 ));
my $rv = $dbh->do($stmt) or die $DBI::errstr;

$stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (2, 'Allen', 25, 'Texas', 15000.00 ));
$rv = $dbh->do($stmt) or die $DBI::errstr;

$stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (3, 'Teddy', 23, 'Norway', 20000.00 ));
$rv = $dbh->do($stmt) or die $DBI::errstr;

$stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 ););
$rv = $dbh->do($stmt) or die $DBI::errstr;

print "Records created successfully\n";
$dbh->disconnect();

當執行上述程式時，它將在COMPANY表中建立/插入給定的記錄，並顯示以下兩行：

Opened database successfully
Records created successfully

SELECT操作

以下Perl程式顯示了如何從上述範例中建立的COMPANY表中獲取和顯示記錄：

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "Pg"; 
my $database = "testdb";
my $dsn = "DBI:$driver:dbname=$database;host=127.0.0.1;port=5432";
my $userid = "postgres";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(SELECT id, name, address, salary  from COMPANY;);
my $sth = $dbh->prepare( $stmt );
my $rv = $sth->execute() or die $DBI::errstr;
if($rv < 0){
   print $DBI::errstr;
}
while(my @row = $sth->fetchrow_array()) {
      print "ID = ". $row[0] . "\n";
      print "NAME = ". $row[1] ."\n";
      print "ADDRESS = ". $row[2] ."\n";
      print "SALARY =  ". $row[3] ."\n\n";
}
print "Operation done successfully\n";
$dbh->disconnect();

執行上述程式時，會產生以下結果：

Opened database successfully
ID = 1
NAME = Paul
ADDRESS = California
SALARY =  20000

ID = 2
NAME = Allen
ADDRESS = Texas
SALARY =  15000

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY =  20000

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY =  65000

Operation done successfully

更新操作

Perl程式碼顯示了如何使用UPDATE語句來更新指定記錄，然後從COMPANY表中獲取和顯示更新的記錄：

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "Pg"; 
my $database = "testdb";
my $dsn = "DBI:$driver:dbname=$database;host=127.0.0.1;port=5432";
my $userid = "postgres";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(UPDATE COMPANY set SALARY = 25000.00 where ID=1;);
my $rv = $dbh->do($stmt) or die $DBI::errstr;
if( $rv < 0 ){
   print $DBI::errstr;
}else{
   print "Total number of rows updated : $rv\n";
}
$stmt = qq(SELECT id, name, address, salary  from COMPANY;);
my $sth = $dbh->prepare( $stmt );
$rv = $sth->execute() or die $DBI::errstr;
if($rv < 0){
   print $DBI::errstr;
}
while(my @row = $sth->fetchrow_array()) {
      print "ID = ". $row[0] . "\n";
      print "NAME = ". $row[1] ."\n";
      print "ADDRESS = ". $row[2] ."\n";
      print "SALARY =  ". $row[3] ."\n\n";
}
print "Operation done successfully\n";
$dbh->disconnect();

執行上述程式時，會產生以下結果：

Opened database successfully
Total number of rows updated : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY =  25000

ID = 2
NAME = Allen
ADDRESS = Texas
SALARY =  15000

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY =  20000

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY =  65000

Operation done successfully

刪除操作

Perl程式碼顯示了如何使用DELETE語句刪除指定記錄，然後從COMPANY表中獲取並顯示剩餘的記錄：

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "Pg"; 
my $database = "testdb";
my $dsn = "DBI:$driver:dbname=$database;host=127.0.0.1;port=5432";
my $userid = "postgres";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(DELETE from COMPANY where ID=2;);
my $rv = $dbh->do($stmt) or die $DBI::errstr;
if( $rv < 0 ){
   print $DBI::errstr;
}else{
   print "Total number of rows deleted : $rv\n";
}
$stmt = qq(SELECT id, name, address, salary  from COMPANY;);
my $sth = $dbh->prepare( $stmt );
$rv = $sth->execute() or die $DBI::errstr;
if($rv < 0){
   print $DBI::errstr;
}
while(my @row = $sth->fetchrow_array()) {
      print "ID = ". $row[0] . "\n";
      print "NAME = ". $row[1] ."\n";
      print "ADDRESS = ". $row[2] ."\n";
      print "SALARY =  ". $row[3] ."\n\n";
}
print "Operation done successfully\n";
$dbh->disconnect();

執行上述程式時，會產生以下結果：

Opened database successfully
Total number of rows deleted : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY =  25000

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY =  20000

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY =  65000

Operation done successfully