Oracle Database Development (6). A first exploration of OCI
Vert Melon
Jun 25,2007
1.Preface
Last time , i provided a full example of OCI , which contains the actual code of connection
and SQL . Certainly it could not cover all of the knowledge , but i think it is a good beginning
for the fresher .
As the same as Pro*C you might confirm that you have installed it correctly . Look at this
paths as follows :
Windows : $ORACLE_HOME\oci
Linux/Unix : $ORACLE_HOME/rdbms/demo
There are many examples offered by ORACLE . Though it seems like a clutter , you also
can get some useful imformation .
The main platform we use here is Linux . And the Windows ? How can i config it in Windows ?
It would be a comfy thing if you have read the chapters recorded in <Oracle Database Development (1). Config OCI In Windows> .
It is easily comprehend by analogy .
2.Something you should know
What is the Oracle Call Interface?
The Oracle Call Interface (OCI) is a set of low-level APIs (Application Programming Interface Calls)
used to interact with Oracle databases. It allows one to use operations like logon, execute,
parse, fetch, etc. OCI programs are normally written in C or C++, although they can be written
in almost any programing language. Unlike with the Oracle Precompilers (like Pro*C and Pro*COBOL),
OCI programs are not precompiled.
Also I have found a official explaination about the choice between Pro*C and OCI .
Should one use OCI or the Oracle Precompilers?
OCI is superior to Pro*C in the following ways:
Performance is much better with OCI
Reduced code size
Direct access to built-in functions (No intermediate files or substitutions).
Piecewise Operation on LONG fields (All LONG field problems are solved)
In Pro*C one cannot dynamically allocate memory to be used as bind variables
You cannot control the Pro*C precompiler to provide better and more compilable C-code.
...
Common problems with OCI:
OCI code is difficult to write and to maintain
Very few people can write, let alone maintain OCI code
...
An OCI application program must do the following:
Connect to one or more databases: call the OCILogon (olog, olon or orlon) routines
Open the cursors needed by the program: use oexec, oexn, ofen or oftech calls.
Process the SQL statements that are needed to perform the application's tasks.
Close the cursors using the oclose routine.
Disconnect from the databases: use ologoff to close an open connection to oracle.
3.Obsolescent OCI Routines
After get through the section "Something you should know" , you may find some strange
words : oexec , ologoff or oclose . There are old routines in preceding release .
Release 8.0 of the Oracle Call Interface introduced an entirely new set of functions which
were not available in release 7.3. Release 8.1 added more new functions. Oracle9i OCI continues
to support these new functions, and adds more new calls. The earlier 7.x calls are still available,
but Oracle strongly recommends that existing applications use the new calls to improve performance
and provide increased functionality.
To get more information , check it in the chapter named "Introduction and Upgrading" in
OCI document .
4. Introduce to OCI Makefile
It's time to make out the source file , and the first one is Makefile which is a trunk in a project .
But then it is the end of a first exploration .
Notice that the head files of OCI are put in two directories and the lib file is libclntsh.so.9.0
which is the same as Pro*C . This is a simple one , just copy the code in last article and
divide into the corresponding files as the list . Then use "make all" or "make clean" to deal with
the source file automaticly . You would see something like this .
[root@liwei oci]# make clean;
rm -f OCIDB OCIDB.o OCIException.o Exception.o OCIError.o Main.o
[root@liwei oci]# make all;
[OCIDB.o]
---------------------
g++ -g -o OCIDB.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c OCIDB.cpp
[OCIException.o]
---------------------
g++ -g -o OCIException.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c OCIException.cpp
[Exception.o]
---------------------
g++ -g -o Exception.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c Exception.cpp
[OCIError.o]
---------------------
g++ -g -o OCIError.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c OCIError.cpp
[Main.o]
---------------------
g++ -g -o Main.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c Main.cpp
[link] ...
---------------------
g++ -g -o OCIDB OCIDB.o OCIException.o Exception.o OCIError.o Main.o -L/home/ora/ora9/oracle/lib -lclntsh
That's good . Take a rest for next step .
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Oracle數(shù)據(jù)庫(kù)開(kāi)發(fā)(六).OCI應(yīng)用初探
草木瓜
2007.6.25
一、序
在上一次，我提供了一個(gè)完整的OCI示例，內(nèi)容包括數(shù)據(jù)庫(kù)連接和SQL操作的實(shí)際代碼。
當(dāng)然一個(gè)小例子不可能包括所有內(nèi)容，不過(guò)我認(rèn)為對(duì)初學(xué)者是一個(gè)不錯(cuò)的開(kāi)始。
與Pro*C一樣，需要確認(rèn)安裝OCI組件，查看下面的路徑：
Windows : $ORACLE_HOME\oci
Linux/Unix : $ORACLE_HOME/rdbms/demo
這些目錄包含一些由ORACLE提供的一些示例。雖然有些雜亂，不過(guò)還是一些幫助的。
我們這里使用的主要平臺(tái)是Linux。 Windows下怎么設(shè)置呢？可以參見(jiàn)《Oracle數(shù)據(jù)庫(kù)
開(kāi)發(fā)(一).Windows下配置使用ProC》一文，都是類似的。
二、一些你需要知道的東西
OCI是什么 ？
OCI是一組底層的API(應(yīng)用程序接口)，主要和Oracle數(shù)據(jù)庫(kù)進(jìn)行交互。你可以調(diào)用一些
操作如 logon , execute, parse, fecth 等等。OCI支持大數(shù)據(jù)語(yǔ)言，通常使用C/C++。與Oracle
Pro*C等不同，OCI不需要預(yù)編譯。
我這里也找著一份關(guān)于在Pro*C和OCI之間選擇的官方說(shuō)明。
我應(yīng)該使用OCI還是Pro*C？
OCI比Pro*C的一些優(yōu)勢(shì)：
OCI的性能十分出色
代碼大量縮減
對(duì)內(nèi)置函數(shù)直接訪問(wèn)
對(duì)LONG類型的分段操作(可以處理LONG相關(guān)的任何錯(cuò)誤)
Pro*C不能為綁定變量動(dòng)態(tài)分配內(nèi)存
不能控制Pro*C自動(dòng)生成的代碼
OCI開(kāi)發(fā)的一些常見(jiàn)問(wèn)題：
OCI代碼不容易掌握
...
OCI開(kāi)發(fā)流程：
連接多個(gè)數(shù)據(jù)庫(kù)：使用OCILogon (olog, olon or orlon)
打開(kāi)游標(biāo)：oexec, oexn, ofen 或者 oftech
執(zhí)行相應(yīng)SQL語(yǔ)句
關(guān)于游標(biāo)：oclose
斷開(kāi)連接：ologoff
三、廢棄的一些程序標(biāo)準(zhǔn)
看過(guò)上節(jié)，你會(huì)發(fā)現(xiàn)一些奇怪的單詞，oexec , ologoff 或 oclose 。這些都是先前版本
舊的OCI標(biāo)準(zhǔn)。
OCI 8.0 引入一套全新的程序結(jié)構(gòu)，是7.3以前沒(méi)有的。8.1版本又?jǐn)U展了一些函數(shù)。
在Oracle 9i中雖然支持這些舊的標(biāo)準(zhǔn)，不過(guò)Oracle強(qiáng)烈建議使用全新的OCI標(biāo)準(zhǔn)庫(kù)。
參考OCI文檔中"介紹和升級(jí)內(nèi)容"一節(jié)，獲取更多信息。
四、OCI Makefile 介紹
現(xiàn)在差不多該介紹源代碼了，首先的是Makefile文件，可以說(shuō)成是整個(gè)項(xiàng)目的中心，參
看例中的文件內(nèi)容。注意頭文件目錄有兩個(gè)，庫(kù)文件和Pro*C使用的一樣，還是 libclntsh.so.9.0 ，
相關(guān)路徑自已調(diào)整。
這個(gè)Makefile比較簡(jiǎn)單，把前面文章羅列的所有代碼復(fù)制并建立相應(yīng)文件，使用"make all"
"make clean" 命令，你應(yīng)該能看到如下類似的內(nèi)容：
[root@liwei oci]# make clean;
rm -f OCIDB OCIDB.o OCIException.o Exception.o OCIError.o Main.o
[root@liwei oci]# make all;
[OCIDB.o]
---------------------
g++ -g -o OCIDB.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c OCIDB.cpp
[OCIException.o]
---------------------
g++ -g -o OCIException.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c OCIException.cpp
[Exception.o]
---------------------
g++ -g -o Exception.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c Exception.cpp
[OCIError.o]
---------------------
g++ -g -o OCIError.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c OCIError.cpp
[Main.o]
---------------------
g++ -g -o Main.o -I/home/ora/ora9/oracle/rdbms/demo -I/home/ora/ora9/oracle/rdbms/public -c Main.cpp
[link] ...
---------------------
g++ -g -o OCIDB OCIDB.o OCIException.o Exception.o OCIError.o Main.o -L/home/ora/ora9/oracle/lib -lclntsh
Makefile相關(guān)知識(shí)可以去Google一下，文章從現(xiàn)在開(kāi)始，就要陸續(xù)介紹一些OCI
實(shí)質(zhì)性的內(nèi)容了。