学习SQLite之路(五) C/C++ SQLite开发实例

  介绍一种乌班图中使用sqlite的用法,非常简单,下面的例子是在乌班图12.04中实现的:

1,先安装两个东西

sudo apt-get install sqlite sqlite3

sudo apt-get install libsqlite3-dev  // 不然可能会报 没有头文件 sqlite3.h

2,C/C++接口:一般用到下面这三个,详情请参考sqlite官方文档。

(1)sqlite3_open(const char *filename, sqlite3 **ppDb)

    打开一个数据库连接, 返回sqlite3对象。

(2)sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char **errmsg)

    解析并执行由 sql 参数所给的每个命令,直到字符串结束或者遇到错误为止。

(3)sqlite3_close(sqlite3*)

    关闭之前打开的数据库。

3、打开数据库并创建表

#include<stdio.h>
#include<sqlite3.h> // 暂时先不管
static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
int i = ;
for(i = ; i < argc; i++)
{
printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
} printf("\n");
return ;
} int main()
{
sqlite3* db;
char *zErrMsg = ;
int rc;
char *sql; rc = sqlite3_open("test.db", &db); // 打开数据库
if(rc)
{
fprintf(stderr, "Can't open database:%s\n", sqlite3_errmsg(db));
// exit(0);
return -;
}
else
{
fprintf(stderr,"open database succeddfully\n");
} sql = "create table company(ID INT PRIMARY KEY NOT NULL, NAME TEXT NOT NULL, AGE TEXT NOT NULL, ADDRESS CHAR(50))"; rc = sqlite3_exec(db, sql, callback, , &zErrMsg); // 执行上面sql中的命令
if(SQLITE_OK != rc)
{
fprintf(stderr, "SQL error: %s\n", zErrMsg);
}
else
{
fprintf(stdout, "create table successfully\n");
} sqlite3_close(db);
return ;
}

运行:需要链接sqlite3库,下面的其他操作也是如此。

 gcc sqlite3test.c -o create -l sqlite3

4、插入数据:

#include<stdio.h>
#include<sqlite3.h> static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
int i = ;
for(i = ; i < argc; i++)
{
printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
} printf("\n");
return ;
} int main()
{
sqlite3* db;
char *zErrMsg = ;
int rc;
char *sql; rc = sqlite3_open("test.db", &db);
if(rc)
{
fprintf(stderr, "Can't open database:%s\n", sqlite3_errmsg(db));
// exit(0);
return -;
}
else
{
fprintf(stderr,"open database succeddfully\n");
} // sql = "create table company(ID INT PRIMARY KEY NOT NULL, NAME TEXT NOT NULL, AGE TEXT NOT NULL, ADDRESS CHAR(50))"; sql = "insert into company(ID, NAME, AGE, ADDRESS) values(1, 'Paul', 25, 'USA');\
insert into company(ID, NAME, AGE, ADDRESS) values(, 'James', , 'JAP');\
insert into company(ID, NAME, AGE, ADDRESS) values(, 'Yao', , 'CHA');\
insert into company(ID, NAME, AGE, ADDRESS) values(, 'kobe', , 'USA');"; rc = sqlite3_exec(db, sql, callback, , &zErrMsg);
if(SQLITE_OK != rc)
{
fprintf(stderr, "SQL error: %s\n", zErrMsg);
}
else
{
fprintf(stdout, "insert table successfully\n");
} sqlite3_close(db);
return ;
}

5、查询数据:

注意:这里的callback函数,是sqlite的一个回调函数,格式如下(必须按照这个格式):
int sqlite_callback(
    void* NotUsed,    /* 由 sqlite3_exec() 的第四个参数传递而来 */
    int argc,        /* 表的列数 */
    char** argv,    /* 指向查询结果的指针数组, 可以由 sqlite3_column_text() 得到 */
    char** azColName /* 指向表头名的指针数组, 可以由 sqlite3_column_name() 得到 */
);

执行sqlite3_exec() 时作为参数传进去。

说明:

参数:
    NotUsed:由sqlite3_exec传递的初始化参数
    argc:表头的列数
    azColName:表头的名字数组指针,在我们的例子就是指向{ID, NAME, AGE, ADDRESS}的指针
    argv:表头的数据数组指针
返回值:
    1:中断查找
    0:继续列举查询到的数据

#include<stdio.h>
#include<sqlite3.h> static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
int i = ;
for(i = ; i < argc; i++)
{
printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
} printf("\n");
return ;
} int main()
{
sqlite3* db;
char *zErrMsg = ;
int rc;
char *sql; rc = sqlite3_open("test.db", &db);
if(rc)
{
fprintf(stderr, "Can't open database:%s\n", sqlite3_errmsg(db));
// exit(0);
return -;
}
else
{
fprintf(stderr,"open database succeddfully\n");
} sql = "select * from company;"; rc = sqlite3_exec(db, sql, callback, , &zErrMsg);
if(SQLITE_OK != rc)
{
fprintf(stderr, "SQL error: %s\n", zErrMsg);
}
else
{
fprintf(stdout, "select table successfully\n");
} sqlite3_close(db);
return ;
}

请看输出:

学习SQLite之路(五) C/C++ SQLite开发实例

6、更新并查询:

#include<stdio.h>
#include<sqlite3.h> static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
int i = ;
for(i = ; i < argc; i++)
{
printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
} printf("\n");
return ;
} int main()
{
sqlite3* db;
char *zErrMsg = ;
int rc;
char *sql; rc = sqlite3_open("test.db", &db);
if(rc)
{
fprintf(stderr, "Can't open database:%s\n", sqlite3_errmsg(db));
// exit(0);
return -;
}
else
{
fprintf(stderr,"open database succeddfully\n");
} sql = "update company set ADDRESS = 'RUS' where ID = 3;\
select * from company;"; rc = sqlite3_exec(db, sql, callback, , &zErrMsg);
if(SQLITE_OK != rc)
{
fprintf(stderr, "SQL error: %s\n", zErrMsg);
}
else
{
fprintf(stdout, "update table successfully\n");
} sqlite3_close(db);
return ;
}

7、删除并查询:

#include<stdio.h>
#include<sqlite3.h> static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
int i = ;
for(i = ; i < argc; i++)
{
printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
} printf("\n");
return ;
} int main()
{
sqlite3* db;
char *zErrMsg = ;
int rc;
char *sql; rc = sqlite3_open("test.db", &db);
if(rc)
{
fprintf(stderr, "Can't open database:%s\n", sqlite3_errmsg(db));
// exit(0);
return -;
}
else
{
fprintf(stderr,"open database succeddfully\n");
} sql = "delete from company where ID = 2;\
select * from company;"; rc = sqlite3_exec(db, sql, callback, , &zErrMsg);
if(SQLITE_OK != rc)
{
fprintf(stderr, "SQL error: %s\n", zErrMsg);
}
else
{
fprintf(stdout, "delete table successfully\n");
} sqlite3_close(db);
return ;
}

8,上面的例子可在下面找到:

https://github.com/xcywt/MySQLite

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