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数据库：

需要导入：sqlite3

添加 删除 修改数据库中的数据都用的是：sqlite3_exec

查询数据库用的是：sqlite3_prepare_v2

// 创建一个sqlite3对象 以后都操作它static sqlite3 *db = nil;#pragma mark   1. 打开数据库- (void)openDB {    if (db == nil) {        NSString *tempPath = NSTemporaryDirectory();        NSLog(@"%@", tempPath);        NSString *filePath = [tempPath stringByAppendingPathComponent:@"student.sqlite"];                // 打开路径下的数据库        int result = sqlite3_open(filePath.UTF8String, &db);        if (result == SQLITE_OK) {            NSLog(@"打开数据库成功");            // 写sql语句(可用某些工具生成SQL语句)            NSString *sql = @"CREATE  TABLE  IF NOT EXISTS student (number INTEGER PRIMARY KEY  NOT NULL , name TEXT, age INTEGER)";            // 执行SQL语句            int result2 = sqlite3_exec(db, sql.UTF8String, NULL, NULL, NULL);            if (result2 == SQLITE_OK) {                NSLog(@"创建表格成功");            }else                NSLog(@"创建表格失败");                    }else            NSLog(@"打开数据库失败");    }}#pragma mark   2. 关闭数据库- (void)closeDB {    if (db != nil) {        int result = sqlite3_close(db);        if (result == SQLITE_OK) {            NSLog(@"关闭数据库成功");            // 同时把数据库对象置空            db = nil;        }else            NSLog(@"关闭数据库失败");    }}#pragma mark   3. 添加数据- (void)insertStudent:(Student *)stu {    // 添加的sql语句    NSString *sql = [NSString stringWithFormat:@"INSERT INTO student (number, name, age) VALUES ('%@', '%@', '%d')", stu.number, stu.name, stu.age];            int result = sqlite3_exec(db, sql.UTF8String, NULL, NULL, NULL);    if (result == SQLITE_OK) {        NSLog(@"添加数据成功");    }else        NSLog(@"添加数据失败");}#pragma mark   4. 删除数据- (void)deleteStudent:(NSString *)num {    NSString *sql = [NSString stringWithFormat:@"DELETE FROM student WHERE number = '%@'", num];    int result = sqlite3_exec(db, sql.UTF8String, NULL, NULL, NULL);    if (result == SQLITE_OK) {         NSLog(@"删除数据成功");    }else         NSLog(@"删除数据失败");}#pragma mark   5. 更新数据- (void)updateStudent:(Student *)stu {    NSString *sql = [NSString stringWithFormat:@"UPDATE student SET name = '%@' , age = '%d' WHERE number = '%@'", stu.name, stu.age, stu.number];    int result = sqlite3_exec(db, sql.UTF8String, nil, nil, nil);    if (result == SQLITE_OK) {        NSLog(@"更新数据成功");    }else        NSLog(@"更新数据失败");    }#pragma mark   6. 查询数据- (NSMutableArray *)selectStudent {    NSMutableArray *arrayAll = [NSMutableArray array];            // 有条件的查询 直接加一个where语句就可以啦    NSString *sql = [NSString stringWithFormat:@"SELECT * FROM student"];            // 游标    sqlite3_stmt *stmt = nil;    // int nByte为-1时：自动计算sql语句的长度    int result = sqlite3_prepare_v2(db, sql.UTF8String, -1, &stmt, NULL);    if (result == SQLITE_OK) {        NSLog(@"开始查找数据");        // 一行一行的去查找数据  直到找完        while (sqlite3_step(stmt) == SQLITE_ROW) {            // 获取number            const char *num1 = (const char *)sqlite3_column_text(stmt, 0);// 第二个参数递增            NSString *number = [NSString stringWithCString:num1 encoding:NSUTF8StringEncoding];            // 获取name            const char *name1 = (const char *)sqlite3_column_text(stmt, 1);            NSString *name = [NSString stringWithCString:name1 encoding:NSUTF8StringEncoding];            // 获取age            int age = sqlite3_column_int(stmt, 2);            // 把取到的数据放到数据模型中            Student *stu = [[Student alloc] init];            stu.name = name;            stu.number = number;            stu.age = age;                        [arrayAll addObject:stu];        }    }else        NSLog(@"查询失败");    // 游标用完之后要释放：    sqlite3_finalize(stmt);    return arrayAll;}

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