Sqlite 简明教程

SQLite - Perl

在本章中，您将了解如何在 Perl 程序中使用 SQLite。

Installation

SQLite3 可以使用 Perl DBI 模块与 Perl 集成，这是一个为 Perl 编程语言而设计的数据库访问模块。它定义了一组方法、变量和约定，从而提供了一个标准数据库界面。

以下是 Linux/UNIX 计算机上安装 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，那么它可以按如下方式安装 −

$ wget http://search.cpan.org/CPAN/authors/id/M/MS/MSERGEANT/DBD-SQLite-1.11.tar.gz
$ tar xvfz DBD-SQLite-1.11.tar.gz
$ cd DBD-SQLite-1.11
$ perl Makefile.PL
$ make
$ make install

DBI Interface APIs

接下来是一些重要的 DBI 例程，它们可以满足您用 Perl 程序操作 SQLite 数据库的需求。如果您正在寻找一个更复杂一些的应用程序，那么可以查阅 Perl DBI 官方文档。

Sr.No.	API & Description
1	DBI→connect($data_source, "", "", \%attr) 建立到请求的 $data_source 的数据库连接（即会话）。如果连接成功，则返回一个数据库句柄对象。Datasource 采用如下形式 − DBI:SQLite:dbname = 'test.db' 其中 SQLite 是 SQLite 驱动程序名称，test.db 是 SQLite 数据库文件的名称。如果将文件名指定为 ':memory:' ，它将在 RAM 中创建一个仅持续会话期间的内存数据库。如果文件名是实际的设备文件名，则它将尝试使用它的值打开数据库文件。如果不存在该名称的文件，则将创建同名的新数据库文件。您可以将第二个和第三个参数保留为空字符串，并且最后一个参数是传递各种属性，如下面的示例所示。
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) 此例程为数据库引擎的稍后执行准备一条语句，并返回对语句句柄对象的引用。
4	$sth→execute() 此例程执行必要的任何处理以执行已准备好的语句。如果发生错误，则返回 undef。成功的执行总是返回 true，无论影响的行数如何。这里，$sth 是 $dbh→prepare($sql) 调用返回的语句句柄。
5	$sth→fetchrow_array() 此例程取回下一行数据并将其作为包含字段值的列表返回。空字段在列表中作为 undef 值返回。
6	$DBI::err 这等同于 $h→err，其中 $h 是任何句柄类型，例如 $dbh、$sth 或 $drh。这将从调用的最后一个驱动程序方法返回本机数据库引擎错误代码。
7	$DBI::errstr 这等同于 $h→errstr，其中 $h 是任何句柄类型，例如 $dbh、$sth 或 $drh。这将从调用的最后一个 DBI 方法返回本机数据库引擎错误消息。
8	$dbh→disconnect() 此例程关闭先前由 DBI→connect() 调用打开的数据库连接。

Connect To Database

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，最后将返回一个数据库对象。

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
   or die $DBI::errstr;

print "Opened database successfully\n";

现在，让我们运行以上程序在当前目录中创建数据库 test.db。您可以根据需要更改路径。将以上代码保留在 sqlite.pl 文件中，并按如下所示执行。如果成功创建数据库，则它将显示以下消息 −

$ chmod +x sqlite.pl
$ ./sqlite.pl
Open database successfully

Create a Table

以下 Perl 程序用于在先前创建的数据库中创建表。

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
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();

在执行以上程序时，它将在 test.db 中创建 COMPANY 表，并显示以下消息 −

Opened database successfully
Table created successfully

NOTE − 万一您在任何操作中看到以下错误 −

DBD::SQLite::st execute failed: not an error(21) at dbdimp.c line 398

在这种情况中，请打开 DBD-SQLite 安装中可用的 dbdimp.c file 并找出 sqlite3_prepare() 函数，然后将其第三个参数更改为 -1 （而不是 0）。最后，使用 make 安装 DBD::SQLite 并执行 make install 以解决问题。

INSERT Operation

以下 Perl 程序演示如何创建以上示例中创建的 COMPANY 表中的记录。

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
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，并且它将显示以下两行：

Opened database successfully
Records created successfully

SELECT Operation

以下 Perl 程序演示如何从以上示例中创建的 COMPANY 表中取回和显示记录。

#!/usr/bin/perl

use DBI;
use strict;

my $driver = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
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，它将产生以下结果。

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 Operation

以下 Perl 代码演示如何使用 UPDATE 语句更新任何记录，然后从 COMPANY 表中取回和显示已更新的记录。

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
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，它将产生以下结果。

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 Operation

以下 Perl 代码演示如何使用 DELETE 语句删除任何记录，然后从 COMPANY 表中取回和显示剩余记录 −

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
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，它将产生以下结果。

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