本文介绍一下sqlite C/C++接口。@H_403_2@

早期的sqlite C/C++接口只有5个接口函数,很容易学习。 新版本的sqlite新增了很多功能,目前大概有185个API接口。本文介绍一些核心的API接口和对象。@H_403_2@

1. 核心对象
数据库连接对象: sqlite3
prepared_statement对象: sqlite3_stmt@H_403_2@

严格的讲 sqlite3_stmt对象也不是必须的， 另外两个封装了qlite3_stmt的接口sqlite3_exec和sqlite3_get_table可以代替sqlite3_stmt对象完成数据存取工作。 但是理解sqlite3_stmt对于充分使用sqlite有很大帮助。@H_403_2@

以下是一些操作 sqlite3和sqlite3_stmt对象的接口。下面这些名字只是提供一个概念，实际的函数可能会有很多版本比如sqlite3_open() 有，sqlite3_open_v16(),sqlite3_open_v2()
sqlite3_open()
sqlite3_prepare()
sqlite3_step()
sqlite3_column()
sqlite3_finalize()
sqlite3_close()@H_403_2@

函数说明
sqlite3_open() 打开一个数据库连接,返回sqlite3对象
sqlite3_prepare() 此函数将sql转换成sqlite3_stmt对象,通常使用sqlite3_prepare_v2()
sqlite3_step() 此函数单步执行sqlite3_stmt
sqlite3_column() 返回 sqlite3_stmt所在行的指定column的值， 有如下具体函数
* sqlite3_column_blob()
* sqlite3_column_bytes()
* sqlite3_column_bytes16()
* sqlite3_column_count()
* sqlite3_column_double()
* sqlite3_column_int()
* sqlite3_column_int64()
* sqlite3_column_text()
* sqlite3_column_text16()
* sqlite3_column_type()
* sqlite3_column_value()@H_403_2@

sqlite3_finalize() 销毁 sqlite3_stmt对象,所有sqlite3_stmt对象都应该销毁以防止内存泄漏
sqlite3_close() 关闭数据库连接,销毁sqlite3对象,所有与这个sqlite3对象相关的sqlite3_stmt对象都应该在调用这个函数之前销毁。@H_403_2@

2. 绑定和重新执行sqlite3_stmt
sqlite3_reset(): 此函数使得执行过sqlite3_step()的sqlite3_stmt重新执行,相当于将游标返回到开始位置重新读取数据,sqlite3_reset()的效率比重新创建一个sqlite3_stmt搞很多。@H_403_2@

sqlite3_bind(): 此函数用于INSERT sql,当同一个INSERT sql要插入一系列数据时使用,每次sqlite3_step()后重新bind数据。@H_403_2@

3. 一般用法和步骤
(1) Create a prepared statement using sqlite3_prepare().
(2) Evaluate the prepared statement by calling sqlite3_step() one or more times.
(3) For queries,extract results by calling sqlite3_column() in between two calls to sqlite3_step().
(4) Destroy the prepared statement using sqlite3_finalize().@H_403_2@

4. 简易接口
sqlite3_get_table()
sqlite3_exec()@H_403_2@

5. 例子@H_403_2@

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01.void basic_interface()
02.{
03. sqlite3 *db;
04. char *zErrMsg = 0;
05. int rc;
06. char sql[]="select * from addr;";
07. sqlite3_stmt *stmt;
08. int id;
09. unsigned char *street,*city;
10. rc = sqlite3_open("D:/VCWork/test.db",&db);
11. if( rc ){
12. fprintf(stderr,"Can't open database: %s/n",sqlite3_errmsg(db));
13. sqlite3_close(db);
14. return;
15. }
16. rc= sqlite3_prepare_v2(db,sql,strlen(sql),&stmt,0);
17. if( rc ){
18. fprintf(stderr,"Can't open statement: %s/n",sqlite3_errmsg(db));
19. sqlite3_close(db);
20. return;
21. }
22. //right align output format
23. printf("%10s %10s %10s/n","id","street","city");
24. printf("%10s %10s %10s/n","---","---");
25. while(sqlite3_step(stmt)==sqlITE_ROW ) {
26. id = sqlite3_column_int(stmt,0);
27. street = (unsigned char*)sqlite3_column_text(stmt,1);
28. city = (unsigned char*)sqlite3_column_text(stmt,2);
29. printf("%10d %10s %10s/n",id,street,city);
30. }
31. sqlite3_finalize(stmt);
32. sqlite3_close(db);
33.}
void basic_interface()
{
sqlite3 *db;
char *zErrMsg = 0;
int rc;
char sql[]="select * from addr;";
sqlite3_stmt *stmt;
int id;
unsigned char *street,*city;
rc = sqlite3_open("D:/VCWork/test.db",&db);
if( rc ){
fprintf(stderr,sqlite3_errmsg(db));
sqlite3_close(db);
return;
}
rc= sqlite3_prepare_v2(db,0);
if( rc ){
fprintf(stderr,sqlite3_errmsg(db));
sqlite3_close(db);
return;
}
//right align output format
printf("%10s %10s %10s/n","city");
printf("%10s %10s %10s/n","---");
while(sqlite3_step(stmt)==sqlITE_ROW ) {
id = sqlite3_column_int(stmt,0);
street = (unsigned char*)sqlite3_column_text(stmt,1);
city = (unsigned char*)sqlite3_column_text(stmt,2);
printf("%10d %10s %10s/n",city);
}
sqlite3_finalize(stmt);
sqlite3_close(db);
}@H_403_2@

参考：@H_403_2@

An Introduction To The sqlite C/C++ Interface@H_403_2@

http://www.sqlite.org/cintro.html