学习SQLite之路（五） C/C++ SQLite开发实例

2021-12-17 04:08:12

　　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 = 0;
    for(i = 0; i < argc; i++)
    {
        printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
    }

    printf("\n");
    return 0;
}

int main()
{
    sqlite3* db;
    char *zErrMsg = 0;
    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 -1;
    }
    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, 0, &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 0;
}

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 = 0;
    for(i = 0; i < argc; i++)
    {
        printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
    }

    printf("\n");
    return 0;
}

int main()
{
    sqlite3* db;
    char *zErrMsg = 0;
    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 -1;
    }
    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(2, 'James', 28, 'JAP');\
        insert into company(ID, NAME, AGE, ADDRESS) values(3, 'Yao', 30, 'CHA');\
        insert into company(ID, NAME, AGE, ADDRESS) values(4, 'kobe', 38, 'USA');";

    rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    if(SQLITE_OK != rc)
    {
        fprintf(stderr, "SQL error: %s\n", zErrMsg);
    }
    else
    {
        fprintf(stdout, "insert table successfully\n");
    }

    sqlite3_close(db);
    return 0;
}

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 = 0;
    for(i = 0; i < argc; i++)
    {
        printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
    }

    printf("\n");
    return 0;
}

int main()
{
    sqlite3* db;
    char *zErrMsg = 0;
    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 -1;
    }
    else
    {
        fprintf(stderr,"open database succeddfully\n");
    }

    sql = "select * from  company;";

    rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    if(SQLITE_OK != rc)
    {
        fprintf(stderr, "SQL error: %s\n", zErrMsg);
    }
    else
    {
        fprintf(stdout, "select table successfully\n");
    }

    sqlite3_close(db);
    return 0;
}

请看输出：

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 = 0;
    for(i = 0; i < argc; i++)
    {
        printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
    }

    printf("\n");
    return 0;
}

int main()
{
    sqlite3* db;
    char *zErrMsg = 0;
    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 -1;
    }
    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, 0, &zErrMsg);
    if(SQLITE_OK != rc)
    {
        fprintf(stderr, "SQL error: %s\n", zErrMsg);
    }
    else
    {
        fprintf(stdout, "update table successfully\n");
    }

    sqlite3_close(db);
    return 0;
}

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 = 0;
    for(i = 0; i < argc; i++)
    {
        printf("%s = %s\n",azColName[i], argv[i]?argv[i]:"NULL");
    }

    printf("\n");
    return 0;
}

int main()
{
    sqlite3* db;
    char *zErrMsg = 0;
    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 -1;
    }
    else
    {
        fprintf(stderr,"open database succeddfully\n");
    }

    sql = "delete from company where ID = 2;\
        select * from company;";

    rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    if(SQLITE_OK != rc)
    {
        fprintf(stderr, "SQL error: %s\n", zErrMsg);
    }
    else
    {
        fprintf(stdout, "delete table successfully\n");
    }

    sqlite3_close(db);
    return 0;
}

8，上面的例子可在下面找到：

https://github.com/xcywt/MySQLite

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