PostgreSQL - Perl 接口

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。 它定义了一组提供标准数据库接口的方法、变量和约定。

以下是在您的 Linux/Unix 机器上安装 DBI 模块的简单步骤 −

$ 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

如果需要为 DBI 安装 SQLite 驱动,那么可以如下安装 −

$ 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 界面之前,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/重新启动 postgres 服务器,以防它未运行 −

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

DBI 接口 API

以下是重要的 DBI 例程,它们可以满足您在 Perl 程序中使用 SQLite 数据库的要求。 如果您正在寻找更复杂的应用程序,那么您可以查看 Perl DBI 官方文档。

S. No. API & Description
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,则返回一个数据库句柄对象。

Datasource 的格式如下: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错误时取消定义的行数。 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)

该例程准备语句供数据库引擎稍后执行,并返回对语句句柄对象的引用。

4

$sth→execute()

该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。 无论受影响的行数如何,成功的执行总是返回 true。 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 字段在列表中作为 undef 值返回。

6

$DBI::err

This is equivalent to $h→err, where $h is any of the handle types like $dbh, $sth, or $drh. This returns native database engine error code from the last driver method called.

7

$DBI::errstr

这等价于 $h→errstr,其中 $h 是任何句柄类型,如 $dbh、$sth 或 $drh。 这会从最后调用的 DBI 方法返回本机数据库引擎错误消息。

8

$dbh->disconnect()

此例程关闭先前通过调用 DBI→connect() 打开的数据库连接。


连接数据库

以下 Perl 代码显示了如何连接到现有数据库。 如果数据库不存在,则创建它,最后返回一个数据库对象。

#!/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,那么它将给出以下消息 −

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();

执行上述程序时,它将在您的 testdb 中创建 COMPANY 表,并显示以下消息 −

Opened database successfully
Table created successfully

插入操作

以下 Perl 程序显示了我们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();

执行上述给定程序时,它将在 COMPANY 表中创建给定记录,并显示以下两行 −

Opened database successfully
Records created successfully

SELECT 操作

以下 Perl 程序展示了我们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();

执行上述给定程序时,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

更新操作

以下 Perl 代码显示了我们如何使用 UPDATE 语句更新任何记录,然后从我们的 COMPANY 表中获取并显示更新的记录 −

#!/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();

执行上述给定程序时,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

删除操作

以下 Perl 代码显示了我们如何使用 DELETE 语句删除任何记录,然后从我们的 COMPANY 表中获取并显示剩余的记录 −

#!/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();

执行上述给定程序时,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