sqlite嵌入式数据库C语言基本操作(1)
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sqlite嵌入式数据库C语言基本操作(1)
sqlite是应用最广泛的嵌入式数据库，没有之一，其详细的介绍参见官方网站（http://sqlite.org）.最新的版本是3.12.2.
C语言的API函数列表见官网SQLite C Interface.这里对一些基本的函数做一个简单的说明。
sqlite3_open: 打开数据库文件.
sqlite3_close: 关闭数据库。
sqlite3_prepare : 编译SQL,准备语句。
sqlite3_step: sqlite3_stmt的方式执行SQL语句。
sqlite3_exec: 执行SQL语句。
sqlite3_finalize: 释放 sqlite3_stmt资源。
sqlite3_bind_int: 绑定SQL语句中int参数。
sqlite3_bind_text: 绑定SQL语句中的字符串参数。
sqlite3_bind_blob: 绑定SQL语句中的二进制参数。
sqlite3_column_int: 遍历数据集，得到一行数据中某列的int值。
sqlite3_column_text: 遍历数据集，得到一行数据某列的字符串值。
sqlite3_column_blob: 遍历数据集，得到一行数据某列的二进制值。
……
以下这个例子做一个简单的insert，和 select 的例子，来讲sqlite3数据库的简单数据操作。
首先建一张简单的表，并插入初始化数据。
create table userinfo (
userid integer,
username char(32),
PRIMARY KEY (userid)
);
insert into userinfo (userid,username) values (1,"Alex");
insert into userinfo (userid,username) values (2,"Allan");
insert into userinfo (userid,username) values (3,"Blizzard");
insert into userinfo (userid,username) values (4,"Bob");
建立对应的数据模型.
typedef struct userinfo_s {
int userid; //用户编号
char username[33]; //用户姓名
struct userinfo_s * next; //下一个用户
} userinfo_t;
得到所有Users的函数
int get_all_userinfos(userinfo_t u){
char sql[512] = "select * from userinfo;"; //sql语句
sqlite3 * db = NULL;
sqlite3_stmt * stmt = NULL;
int ret_open = sqlite3_open("test.db",&db); //打开数据库文件
if (ret_open != SQLITE_OK){
printf("open test.db fail\n");
return -1;
}
int ret = sqlite3_prepare(db,sql,-1,&stmt,NULL); //准备好SQL语句
if (ret != SQLITE_OK){
printf("prepare fail \n");
return ret;
}
ret = sqlite3_step(stmt); //执行SQL
int count = 0;
if(ret != SQLITE_ROW){ //返回有数据
return 0;
}else{
userinfo_t * p = u; //建立链表
do{
userinfo_t * user = calloc(sizeof(userinfo_t),1);
user->userid = sqlite3_column_int(stmt,0); //得到USerid 注意get的初始值为index为0
const char * name = sqlite3_column_text(stmt,1); //得到用户名
if (name){
int len = strlen(name);
strncpy(user->username,name,len);
}
user->next = NULL;
p->next = user; //串联 建立一个单项链表
p = p->next;
count ++;
}while((ret = sqlite3_step(stmt))==SQLITE_ROW); //取值下一个
}
sqlite3_finalize(stmt); //释放资源 stmt
sqlite3_close(db); //关闭数据库句柄
return count;
}
insert操作函数：
int insert_userinfo_t(userinfo_t * u){
char sql[512] = "insert into userinfo (userid,username) values (?,?)"; //插入数据库语句
sqlite3 *db = NULL;
sqlite3_stmt * stmt = NULL;
int ret_open = sqlite3_open("test.db",&db); //打开数据库
if(ret_open !=SQLITE_OK){
printf("open test.db fail\n");
return -1;
}
int ret = sqlite3_prepare(db,sql,-1,&stmt,NULL); //准备语句
if (ret != SQLITE_OK){
printf("prepare fail \n");
return ret;
}
sqlite3_bind_int(stmt,1,u->userid); //绑定参数, 注意绑定参数的初始index值为1
sqlite3_bind_text(stmt,2,u->username,32,NULL);
ret = sqlite3_step(stmt); //执行语句
if(ret == SQLITE_DONE){ //执行结果
ret = SQLITE_OK;
}
sqlite3_finalize(stmt); //释放资源
sqlite3_close(db); //关闭数据库
return ret;
}
测试代码:
void test_get_all_userinfos(){
userinfo_t u;
int count = get_all_userinfos(&u);
userinfo_t * p = u.next;
userinfo_t * q = p;
printf("count:%d\n",count);
while(p){
printf("userid:%d username:%s \n",p->userid,p->username);
p = p->next;
}
free_userinfo_t(&u);
}
void test_insert_into_userinfo_t(){
userinfo_t new_user;
new_user.userid = 5;
char new_name[33]= "micheal";
strncpy(new_user.username,new_name,32);
int ret= insert_userinfo_t(&new_user);
printf("ret = %d\n",ret);
}
gcc编译最后记得加上 -lsqlite3
本文只是很初略的介绍了sqlite嵌入式数据库的基本操作，初略到甚至例程只讲了两个操作，增加和查询，修改和删除都没有讲到，不过看了增加操作，修改和删除操作就很容易实现了。
写这篇文章目的只是一个想讲一个过程，一个操作数据库的基本过程
一个数据库操作流程
1 打开数据库
2 编译准备SQL语句
3 绑定SQL语句参数
4 执行SQL语句
5 关闭释放Statement
6 关闭数据库
当然也只是一个初略的流程，对于数据库操作失败的流程处理也没有。不过了解上面这个初略的流程就可以了。更深入的讲解请参见下篇:[sqlite嵌入式数据库C语言基本操作(2)]
参考文献:
sqlite官方网站:sqlite.org
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