打开

-(void)opensqlite:(NSString *)sqliteName{
    if (!sqliteName || sqliteName.length <= 0) {
        NSAssert(sqliteName,@"sqliteName is null");
    }
    if (!db) {
        NSString *basePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES) firstObject];

        NSString *path = [basePath stringByAppendingPathComponent:sqliteName];
        NSLog(@"sqlite 存放位置:%@",path);
        //打开数据库,若存在则打开;反之不存在就创建一个数据库再打开
        int result = sqlite3_open([path UTF8String],&db);
        if (result == sqlITE_OK) {
            NSLog(@"数据库打开成功");
            return;
        } else {
            NSLog(@"数据库打开失败");

        }

    }
}

创建表 & 删除表（表结构）

- (BOOL)createTable{
    NSString *sql = @"create table if not exists 'student' ('number' integer primary key autoincrement not null,'name' text,'sex' text,'age' integer,'score' integer default 0);";
    char *error = NULL;
    int result = sqlite3_exec(db,[sql UTF8String],nil,&error);
    return (result == sqlITE_OK);
}
-(void)dropTable{
    NSString *sql = @"DROP TABLE if EXISTS student;";
    char *error = NULL;
    int ret = sqlite3_exec(db,NULL,&error);
    if (ret == sqlITE_OK) {
        NSLog(@"删除表格成功");
    } else {
        NSLog(@"删除失败:%s",error);
    }
}

表的增删改查

- (void)insertData{
    NSString *sql = @"INSERT INTO student (name,sex,age,score) VALUES ('yy','1',28,99);";
    char *error = NULL;

    int ret = sqlite3_exec(db,NULL,&error);
    if (ret == sqlITE_OK) {
        NSLog(@"插入成功");
    } else {
        NSLog(@"插入失败:%s",error);
    }
}
- (void)deleteData{
    NSString *sql = @"DELETE FROM student WHRER number = 1;";
    int ret = sqlite3_exec(db,NULL);
    if (ret == sqlITE_OK) {
        NSLog(@"删除成功");
    } else {
        NSLog(@"删除失败");
    }
}
- (void) selectData{
    NSString *sql = @"SELECT name,score FROM student;";
    sqlite3_stmt *stmt;
    int ret = sqlite3_prepare_v2(db,-1,&stmt,NULL);
    if (ret == sqlITE_OK) {
        // 查询成功 遍历结果集
        while (sqlite3_step(stmt) == sqlITE_ROW) {
             const unsigned char *name = sqlite3_column_text(stmt,0);
            NSInteger score = sqlite3_column_int(stmt,1);
            NSLog(@"%@ 分数 %ld",[NSString stringWithUTF8String:(const char *)name],(long)score);
        }

    } else {
        NSLog(@"查询失败");

    }
}

解决打印乱码问题
Sending 'const unsigned char *' to parameter of type 'const char * _Nonnull' converts between pointer

强制转化

const unsigned char *name = sqlite3_column_text(stmt,0); NSInteger score = sqlite3_column_int(stmt,1); NSLog(@"%@ 分数 %ld",[NSString stringWithUTF8String:(const char *)name],(long)score);