PostgreSQL - Perl 接口

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安装

PostgreSQL 可以使用 Perl DBI 模块与 Perl 集成，该模块是 Perl 编程语言的数据库访问模块。它定义了一套方法、变量和约定，提供标准的数据库接口。

以下是安装 DBI 模块到 Linux/Unix 系统的简单步骤：

$ 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

如果您需要安装 DBI 的 SQLite 驱动程序，则可以按如下方式安装：

$ 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

在开始使用 Perl PostgreSQL 接口之前，请在 PostgreSQL 安装目录中找到 **pg_hba.conf** 文件，并添加以下行：

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

您可以使用以下命令启动/重启 postgres 服务器（如果未运行）：

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

DBI 接口 API

以下是重要的 DBI 函数，足以满足您从 Perl 程序使用 SQLite 数据库的需求。如果您正在寻找更复杂的应用程序，则可以查看 Perl DBI 官方文档。

序号 API & 描述
1

DBI→connect($data_source, "userid", "password", \%attr)

建立到请求的 $data_source 的数据库连接或会话。如果连接成功，则返回数据库句柄对象。

数据源具有以下形式：**DBI:Pg:dbname=$database;host=127.0.0.1;port=5432** Pg 是 PostgreSQL 驱动程序名称，testdb 是数据库的名称。
2

$dbh→do($sql)

此例程准备并执行单个 SQL 语句。返回受影响的行数，或在出错时返回 undef。返回值 -1 表示行数未知、不适用或不可用。这里 $dbh 是 DBI→connect() 调用返回的句柄。
3

$dbh→prepare($sql)

此例程准备稍后由数据库引擎执行的语句，并返回对语句句柄对象的引用。
4

$sth→execute()

此例程执行执行准备好的语句所需的任何处理。如果发生错误，则返回 undef。成功的执行总是返回 true，无论受影响的行数是多少。这里 $sth 是 $dbh→prepare($sql) 调用返回的语句句柄。
5

$sth→fetchrow_array()

此例程获取下一行数据并将其作为包含字段值的列表返回。NULL 字段在列表中返回为 undef 值。
6

$DBI::err

这相当于 $h→err，其中 $h 是任何句柄类型，例如 $dbh、$sth 或 $drh。这将返回上次调用的驱动程序方法的本机数据库引擎错误代码。
7

$DBI::errstr

这相当于 $h→errstr，其中 $h 是任何句柄类型，例如 $dbh、$sth 或 $drh。这将返回上次调用的 DBI 方法的本机数据库引擎错误消息。
8

$dbh->disconnect()

此例程关闭先前由 DBI→connect() 调用打开的数据库连接。

连接到数据库

以下 Perl 代码演示如何连接到现有数据库。如果数据库不存在，则将创建它，最后返回数据库对象。

#!/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";

现在，让我们运行上面给出的程序来打开我们的数据库 **testdb**；如果数据库成功打开，它将显示以下消息：

Open database successfully

创建表

以下 Perl 程序将用于在先前创建的数据库中创建表：

#!/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();

执行上述程序后，它将在您的 **testdb** 中创建 COMPANY 表，并将显示以下消息：

Opened database successfully
Table created successfully

INSERT 操作

以下 Perl 程序演示了如何在上面示例中创建的 COMPANY 表中创建记录：

#!/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();

执行上述程序后，它将在 COMPANY 表中创建给定的记录，并将显示以下两行：

Opened database successfully
Records created successfully

SELECT 操作

以下 Perl 程序演示了如何从上面示例中创建的 COMPANY 表中获取和显示记录：

#!/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();

执行上述程序后，将产生以下结果：

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

UPDATE 操作

以下 Perl 代码演示了如何使用 UPDATE 语句更新任何记录，然后从我们的 COMPANY 表中获取和显示更新后的记录：

#!/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();

执行上述程序后，将产生以下结果：

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

DELETE 操作

以下 Perl 代码演示了如何使用 DELETE 语句删除任何记录，然后从我们的 COMPANY 表中获取和显示剩余的记录：

#!/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();

执行上述程序后，将产生以下结果：

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
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