循序渐进PostgreSQL: 学习pqxx C++ API访问
习惯了C++来开发的人，可能更倾向于使用c++库来访问PostgreSQL。libpqxx很早以前就推出了。目前已经到了4.0版。本文就简单的介绍
1. 简介
习惯了C++来开发的人，可能更倾向于使用c++库来访问PostgreSQL。libpqxx很早以前就推出了。目前已经到了4.0版。本文就简单的介绍如何使用它，，Linux平台编译相对简单，这里就介绍一下Windows平台下的使用。
libpqxx的下载地址：直接上这里
由于libpqxx对libpq的C-API进行了很好的封装，从而可以节省大量的编码时间。
2. 编译过程
将libpqxx解压到一固定目录。你需要提前编译好或安装好的客户端库，通常为了方便，这里假定你已经有一个PG的安装版或者解压缩版，在c:\pgsql里头。以PG9.x为例。
1. 进入libpqxx源码目录，备份并修改win32\common文件，将PGSQLSRC的值指向正确的地方：
这里是PGSQLSRC="c:\pgsql"
后边还有很多目录位置需要调整，针对我们这种情况，通常都是保留安装版本的设置，如：LIBPQINC=$(PGSQLSRC)\include, 而注释掉#LIBPQINC=$(PGSQLSRC)\interfaces\libpq, 其它几个值都如此类推。
2. 拷贝一些编译相关的头文件
针对具体版本，9.0的，将config\sample-headers\libpq\9.0\pqxx复制到include下边
针对VS2008的，将config\sample-headers\compiler\VisualStudio2008\pqxx复制到include目录下边, 如果是VS2005，以此类推。
3. 编译
program files->VS2008-->Visual studio tools->Visual Studio 2008 Command Prompt, 进入命令行， 在此进入libpqxx的源代码根目录，执行：
nmake /f win32\vc-libpqxx.mak ALL,
得到如下中间过程:
link.exe kernel32.lib ws2_32.lib advapi32.lib /nologo /dll /machine:I386
shell32.lib secur32.lib wldap32.lib /libpath:"C:\hisql-x86-2.0.1"\lib libpq.lib
"ObjDllRelease\binarystring.obj" "ObjDllRelease\connection.obj" "ObjDllRelea
se\connection_base.obj" "ObjDllRelease\cursor.obj" "ObjDllRelease\dbtransactio
n.obj" "ObjDllRelease\errorhandler.obj" "ObjDllRelease\except.obj" "ObjDllRel
ease\field.obj" "ObjDllRelease\largeobject.obj" "ObjDllRelease\nontransaction.
obj" "ObjDllRelease\notification.obj" "ObjDllRelease\notify-listen.obj" "ObjD
llRelease\pipeline.obj" "ObjDllRelease\prepared_statement.obj" "ObjDllRelease\
result.obj" "ObjDllRelease\robusttransaction.obj" "ObjDllRelease\statement_par
ameters.obj" "ObjDllRelease\strconv.obj" "ObjDllRelease\subtransaction.obj" "
ObjDllRelease\tablereader.obj" "ObjDllRelease\tablestream.obj" "ObjDllRelease\
tablewriter.obj" "ObjDllRelease\transaction.obj" "ObjDllRelease\transaction_ba
se.obj" "ObjDllRelease\tuple.obj" "ObjDllRelease\util.obj" "ObjDllRelease\lib
pqxx.obj" /out:"lib\libpqxx.dll" /implib:"lib\libpqxx.lib"
Creating library lib\libpqxx.lib and object lib\libpqxx.exp
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link.exe kernel32.lib ws2_32.lib advapi32.lib /nologo /dll /machine:I386
shell32.lib secur32.lib wldap32.lib /libpath:"C:\hisql-x86-2.0.1"\lib libpq.lib
"ObjDllRelease\binarystring.obj" "ObjDllRelease\connection.obj" "ObjDllRelea
se\connection_base.obj" "ObjDllRelease\cursor.obj" "ObjDllRelease\dbtransactio
n.obj" "ObjDllRelease\errorhandler.obj" "ObjDllRelease\except.obj" "ObjDllRel
ease\field.obj" "ObjDllRelease\largeobject.obj" "ObjDllRelease\nontransaction.
obj" "ObjDllRelease\notification.obj" "ObjDllRelease\notify-listen.obj" "ObjD
llRelease\pipeline.obj" "ObjDllRelease\prepared_statement.obj" "ObjDllRelease\
result.obj" "ObjDllRelease\robusttransaction.obj" "ObjDllRelease\statement_par
ameters.obj" "ObjDllRelease\strconv.obj" "ObjDllRelease\subtransaction.obj" "
ObjDllRelease\tablereader.obj" "ObjDllRelease\tablestream.obj" "ObjDllRelease\
tablewriter.obj" "ObjDllRelease\transaction.obj" "ObjDllRelease\transaction_ba
se.obj" "ObjDllRelease\tuple.obj" "ObjDllRelease\util.obj" "ObjDllRelease\lib
pqxx.obj" /out:"lib\libpqxx.dll" /implib:"lib\libpqxx.lib"
Creating library lib\libpqxx.lib and object lib\libpqxx.exp
link.exe kernel32.lib ws2_32.lib advapi32.lib /nologo /dll /machine:I386
shell32.lib secur32.lib wldap32.lib /libpath:"C:\hisql-x86-2.0.1"\lib libpq.lib
"ObjDllRelease\binarystring.obj" "ObjDllRelease\connection.obj" "ObjDllRelea
se\connection_base.obj" "ObjDllRelease\cursor.obj" "ObjDllRelease\dbtransactio
n.obj" "ObjDllRelease\errorhandler.obj" "ObjDllRelease\except.obj" "ObjDllRel
ease\field.obj" "ObjDllRelease\largeobject.obj" "ObjDllRelease\nontransaction.
obj" "ObjDllRelease\notification.obj" "ObjDllRelease\notify-listen.obj" "ObjD
llRelease\pipeline.obj" "ObjDllRelease\prepared_statement.obj" "ObjDllRelease\
result.obj" "ObjDllRelease\robusttransaction.obj" "ObjDllRelease\statement_par
ameters.obj" "ObjDllRelease\strconv.obj" "ObjDllRelease\subtransaction.obj" "
ObjDllRelease\tablereader.obj" "ObjDllRelease\tablestream.obj" "ObjDllRelease\
tablewriter.obj" "ObjDllRelease\transaction.obj" "ObjDllRelease\transaction_ba
se.obj" "ObjDllRelease\tuple.obj" "ObjDllRelease\util.obj" "ObjDllRelease\lib
pqxx.obj" /out:"lib\libpqxx.dll" /implib:"lib\libpqxx.lib"
Creating library lib\libpqxx.lib and object lib\libpqxx.exp 最终会在lib目录下生成：
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D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0>dir/b/s lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpq.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpq.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.dll.manifest
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.exp
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.dll.manifest
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.exp
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.ilk
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.pdb
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx_static.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx_staticD.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\msdia80.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0>dir/b/s lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpq.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpq.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.dll.manifest
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.exp
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.dll
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.dll.manifest
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.exp
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.ilk
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxxD.pdb
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx_static.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\libpqxx_staticD.lib
D:\Projects\hisql.svn\trunk\learning\libpqxx-4.0\lib\msdia80.dll
下边来看看最简单的示例：
iihero=# create user foo password 'foo1';
CREATE ROLE
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iihero=> create table t(id int primary key, col2 varchar(32));
注意: CREATE TABLE / PRIMARY KEY 将要为表 "t" 创建隐含索引 "t_pkey"
CREATE TABLE
iihero=> \encoding
GBK
iihero=> insert into t values(1 ,'不同类型的列表');
INSERT 0 1
iihero=> select * from t;
id | col2
----+----------------
1 | 不同类型的列表
(1 行记录)
iihero=> create table t(id int primary key, col2 varchar(32));
注意: CREATE TABLE / PRIMARY KEY 将要为表 "t" 创建隐含索引 "t_pkey"
CREATE TABLE
iihero=> \encoding
GBK
iihero=> insert into t values(1 ,'不同类型的列表');
INSERT 0 1
iihero=> select * from t;
id | col2
----+----------------
1 | 不同类型的列表
(1 行记录)
将编译出来后的include, lib目录提取到固定的目录，与你原来的postgresql的include和lib目录，可以合到一起。给开发使用。
下边是一个最简单的示例：
[cpp] view plaincopyprint?
#include#include
int main()
{
pqxx::connection conn("dbname=iihero hostaddr=127.0.0.1 user=foo password=foo1" );
if(conn.is_open())
{
std::cout
std::cout
}
else
{
std::cout
}
pqxx::work w(conn);
pqxx::result res = w.exec("SELECT 1");
w.commit();
std::cout ()
}