SQLite数据库的使用（图片在数据库中的存取）

    // 数据库存放的目录
    NSString *dbPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/test2.db"];
    NSLog(@"dbPath : %@",dbPath);
    
    // 如果数据库文件不存在，自动创建，否则打开数据库
    sqlite3 *database;
    int ret = sqlite3_open([dbPath UTF8String],&database);
    if (ret != SQLITE_OK) {
        NSLog(@"database open failed!");
        return;
    }
    
    // SQL语句
    NSString *sql = @"CREATE TABLE IF NOT EXISTS history (hid integer primary key autoincrement not null,image blob)";
    
    // 创建会话
    sqlite3_stmt *stmt;
    ret = sqlite3_prepare_v2(database,[sql UTF8String],sql.length,&stmt,NULL);
    if (ret != SQLITE_OK) {
        NSLog(@"create statement failed!");
        sqlite3_close(database);
        return;
    }
    
    // 执行SQL语句
    ret = sqlite3_step(stmt);
    if (ret != SQLITE_DONE) {
        NSLog(@"step failed!");
        
        // 终止会话
        sqlite3_finalize(stmt);
        sqlite3_close(database);
        return;
    }
    
    // 插入数据
    NSString *insertImage = @"INSERT INTO history (image) VALUES(?)";
    ret = sqlite3_prepare_v2(database,[insertImage UTF8String],-1,NULL);
    if (ret != SQLITE_OK) {
        NSLog(@"prepare stmt2 failed");
        sqlite3_close(database);
        return;
    }
    
    // 给会话绑定图片数据
    UIImage *image = [UIImage imageNamed:@"login.jpg"];
    NSData *imageData = UIImageJPEGRepresentation(image,0.5);
    
    sqlite3_bind_blob(stmt,1,[imageData bytes],[imageData length],NULL);
    ret = sqlite3_step(stmt);
    if (ret != SQLITE_DONE) {
        NSLog(@"insert stmt failed");
        sqlite3_finalize(stmt);
        sqlite3_close(database);
        return;
    }
    
    // 查询数据
    NSString *selectSQL = @"SELECT * FROM history";
    sqlite3_prepare_v2(database,[selectSQL UTF8String],NULL);
    // 每次只会取一行数据
    int result = sqlite3_step(stmt);
    while (result == SQLITE_ROW) {
        // 取出图片
        const void *image = sqlite3_column_blob(stmt,1);
        int length = sqlite3_column_bytes(stmt,1);
        NSData *imageData = [NSData dataWithBytes:image length:length];
        // 写出去
        [imageData writeToFile:@"/Users/apple/Desktop/shabi.jpg" atomically:YES];
        
        result = sqlite3_step(stmt);
    }
    
    sqlite3_finalize(stmt);
    sqlite3_close(database);

（编辑：李大同）

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