PostgreSQL Perl 接口
PostgreSQL 可以使用 Perl DBI 模块与 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。
以下是在 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,请找到 pg_hba.conf 在 PostgreSQL 安装目录中的文件中添加以下行:
# IPv4 local connections: host all all 127.0.0.1/32 md5
你可以启动/重启 postgres 服务器,如果它没有运行,请使用以下命令:
[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,它们可以满足你从 Perl 程序使用 SQLite 数据库的要求。如果你正在寻找更复杂的应用程序,那么你可以查看 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 $data_source 的数据库连接或会话。如果连接成功,则返回数据库句柄对象。 数据源的形式如下: DBI:Pg:dbname=$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 undef 出错。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 |
$dbh→准备($sql) 该例程为数据库引擎稍后执行准备一条语句,并返回对语句句柄对象的引用。 |
4 |
$sth→执行() 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。空字段作为列表中的 undef 值返回。 |
6 |
$DBI::错误 这等效于 $h→err,其中 $h 是任何句柄类型,如 $dbh、$sth 或 $drh。这将从上次调用的驱动程序方法返回本机数据库引擎错误代码。 |
7 |
$DBI::errstr 这等效于 $h→errstr,其中 $h 是任何句柄类型,如 $dbh、$sth 或 $drh。这将返回来自最后调用的 DBI 方法的本机数据库引擎错误消息。 |
8 |
$dbh->断开() 该例程关闭先前通过调用 DBI→connect() 打开的数据库连接。 |
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,则将创建它并最终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 ;如果数据库打开成功,会提示如下信息:
Open database successfully
创建表
下面的 Perl 程序将用于在之前创建的数据库中创建一个表:
#!/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();
当上面给出的程序被执行时,它会在你的目录中创建 COMPANY 表 testdb 它将显示以下消息:
Opened database successfully Table created successfully
插入操作
下面的 Perl 程序展示了我们如何在上面例子中创建的 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();
当上面给定的程序被执行时,它会在 COMPANY 表中创建给定的记录,并会显示以下两行:
Opened database successfully Records created successfully
选择操作
下面的 Perl 程序展示了我们如何从上面例子中创建的 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();
当上面给出的程序被执行时,它会产生以下结果:
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
下面的 Perl 代码展示了我们如何使用 UPDATE 语句来更新任何记录,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();
当上面给出的程序被执行时,它会产生以下结果:
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
下面的 Perl 代码展示了我们如何使用 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();
当上面给出的程序被执行时,它会产生以下结果:
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