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📜  PostgreSQL-Perl接口

📅  最后修改于: 2020-11-26 06:43:28             🧑  作者: Mango

安装

可以使用Perl DBI模块将PostgreSQL与Perl集成，Perl DBI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。

这是在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

如果您需要为DBI安装SQLite驱动程序，则可以如下安装-

$ 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

如果未运行postgres服务器，则可以使用以下命令启动/重新启动它：

[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，这些例程可以满足您在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，则可以查阅Perl DBI官方文档。

S. No. API & Description
1

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

Establishes a database connection, or session, to the requested $data_source. Returns a database handle object if the connection succeeds.

Datasource has the form like : DBI:Pg:dbname=$database;host=127.0.0.1;port=5432 Pg is PostgreSQL driver name and testdb is the name of database.
2

$dbh→do($sql)

This routine prepares and executes a single SQL statement. Returns the number of rows affected or undef on error. A return value of -1 means the number of rows is not known, not applicable, or not available. Here $dbh is a handle returned by DBI→connect() call.
3

$dbh→prepare($sql)

This routine prepares a statement for later execution by the database engine and returns a reference to a statement handle object.
4

$sth→execute()

This routine performs whatever processing is necessary to execute the prepared statement. An undef is returned if an error occurs. A successful execute always returns true regardless of the number of rows affected. Here $sth is a statement handle returned by $dbh→prepare($sql) call.
5

$sth→fetchrow_array()

This routine fetches the next row of data and returns it as a list containing the field values. Null fields are returned as undef values in the list.
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

This is equivalent to $h→errstr, where $h is any of the handle types like $dbh, $sth, or $drh. This returns the native database engine error message from the last DBI method called.
8

$dbh->disconnect()

This routine closes a database connection previously opened by a call to DBI→connect().

连接到数据库

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，则将创建该数据库，最后将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，让我们运行上述给定的程序以打开数据库testdb ；如果数据库成功打开，则将给出以下消息-

Open database successfully

建立表格

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();

执行上述给定程序后，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

插入操作

以下Perl程序显示了如何在上例中创建的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

选择操作

以下Perl程序说明了如何从上例中创建的COMPANY表中获取并显示记录-

#!/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();

执行上面给定的程序时，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

UPDATE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();

执行上面给定的程序时，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COMPANY表中获取并显示其余记录-

#!/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();

执行上面给定的程序时，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