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SQLite – Perl | 小熊教程

SQLite – Perl

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安装

SQLite3 可使用 Perl DBI 模块与 Perl 进行集成。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、变量及规则。

下面显示了在 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,那么可按照以下步骤进行安装:

 $ 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 接口 API

以下是重要的 DBI 程序,可以满足您在 Perl 程序中使用 SQLite 数据库的需求。如果您需要了解更多细节,请查看 Perl DBI 官方文档。

序号 API & 描述
1 DBI->connect($data_source, “”, “”, /%attr)

建立一个到被请求的 $data_source 的数据库连接或者 session。如果连接成功,则返回一个数据库处理对象。

数据源形式如下所示: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。如果文件名 filename 赋值为 ‘:memory:’,那么它将会在 RAM 中创建一个内存数据库,这只会在 session 的有效时间内持续。

如果文件名 filename 为实际的设备文件名称,那么它将使用这个参数值尝试打开数据库文件。如果该名称的文件不存在,那么将创建一个新的命名为该名称的数据库文件。

您可以保留第二个和第三个参数为空白字符串,最后一个参数用于传递各种属性,详见下面的实例讲解。

2 $dbh->do($sql)

该例程准备并执行一个简单的 SQL 语句。返回受影响的行数,如果发生错误则返回 undef。返回值 -1 意味着行数未知,或不适用 ,或不可用。在这里,$dbh 是由 DBI->connect() 调用返回的处理。

3 $dbh->prepare($sql)

该例程为数据库引擎后续执行准备一个语句,并返回一个语句处理对象。

4 $sth->execute()

该例程执行任何执行预准备的语句需要的处理。如果发生错误则返回 undef。如果成功执行,则无论受影响的行数是多少,总是返回 true。在这里,$sth 是由 $dbh->prepare($sql) 调用返回的语句处理。

5 $sth->fetchrow_array()

该例程获取下一行数据,并以包含各字段值的列表形式返回。在该列表中,Null 字段将作为 undef 值返回。

6 $DBI::err

这相当于 $h->err。其中,$h 是任何的处理类型,比如 $dbh、$sth 或 $drh。该程序返回最后调用的驱动程序(driver)方法的数据库引擎错误代码。

7 $DBI::errstr

这相当于 $h->errstr。其中,$h 是任何的处理类型,比如 $dbh、$sth 或 $drh。该程序返回最后调用的 DBI 方法的数据库引擎错误消息。

8 $dbh->disconnect()

该例程关闭之前调用 DBI->connect() 打开的数据库连接。

连接数据库

下面的 Perl 代码显示了如何连接到一个现有的数据库。如果数据库不存在,那么它就会被创建,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,让我们来运行上面的程序,在当前目录中创建我们的数据库 test.db。您可以根据需要改变路径。保存上面代码到 sqlite.pl 文件中,并按如下所示执行。如果数据库成功创建,那么会显示下面所示的消息:

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

创建表

下面的 Perl 代码段将用于在先前创建的数据库中创建一个表:

 #!/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(); 

上述程序执行时,它会在 test.db 中创建 COMPANY 表,并显示下面所示的消息:

 Opened database successfully Table created successfully 

注意:如果您在任何操作中遇到了下面的错误: in case you see following error in any of the operation:

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

在这种情况下,您已经在 DBD-SQLite 安装中打开了可用的 dbdimp.c 文件,找到 sqlite3_prepare() 函数,并把它的第三个参数 0 改为 -1。最后使用 makemake install 安装 DBD::SQLite,即可解决问题。 in this case you will have open dbdimp.c file available in DBD-SQLite installation and find out sqlite3_prepare() function and change its third argument to -1 instead of 0. Finally install DBD::SQLite using make and do make install to resolve the problem.

INSERT 操作

下面的 Perl 程序显示了如何在上面创建的 COMPANY 表中创建记录:

 #!/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(); 

上述程序执行时,它会在 COMPANY 表中创建给定记录,并会显示以下两行:

 Opened database successfully Records created successfully 

SELECT 操作

下面的 Perl 程序显示了如何从前面创建的 COMPANY 表中获取并显示记录:

 #!/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(); 

上述程序执行时,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 

UPDATE 操作

下面的 Perl 代码显示了如何使用 UPDATE 语句来更新任何记录,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   = "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(); 

上述程序执行时,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 

DELETE 操作

下面的 Perl 代码显示了如何使用 DELETE 语句删除任何记录,然后从 COMPANY 表中获取并显示剩余的记录:

 #!/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(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(); 

上述程序执行时,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 
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