一、简单说明
1.什么是FMDB
FMDB是iOS平台的SQLite数据库框架
FMDB以OC的方式封装了SQLite的C语言API

2.FMDB的优点

使用起来更加面向对象，省去了很多麻烦、冗余的C语言代码
对比苹果自带的Core Data框架，更加轻量级和灵活
提供了多线程安全的数据库操作方法，有效地防止数据混乱

3.FMDB的github地址

https://github.com/ccgus/fmdb

二、核心类

FMDB有三个主要的类
（1）FMDatabase
一个FMDatabase对象就代表一个单独的SQLite数据库
用来执行SQL语句
（2）FMResultSet
使用FMDatabase执行查询后的结果集
（3）FMDatabaseQueue
用于在多线程中执行多个查询或更新，它是线程安全的

三、打开数据库

通过指定SQLite数据库文件路径来创建FMDatabase对象
FMDatabase *db = [FMDatabase databaseWithPath:path];
if (![db open]) {
    NSLog(@"数据库打开失败！");
}
文件路径有三种情况
（1）具体文件路径
　　如果不存在会自动创建
（2）空字符串@""
　　会在临时目录创建一个空的数据库
　　当FMDatabase连接关闭时，数据库文件也被删除
（3）nil
　　会创建一个内存中临时数据库，当FMDatabase连接关闭时，数据库会被销毁

四、执行更新

在FMDB中，除查询以外的所有操作，都称为“更新”
create、drop、insert、update、delete等
使用executeUpdate:方法执行更新
- (BOOL)executeUpdate:(NSString*)sql, ...
- (BOOL)executeUpdateWithFormat:(NSString*)format, ...
- (BOOL)executeUpdate:(NSString*)sql withArgumentsInArray:(NSArray *)arguments
示例
[db executeUpdate:@"UPDATE t_student SET age = ? WHERE name = ?;", @20, @"Jack"]

五、执行查询

查询方法
- (FMResultSet *)executeQuery:(NSString*)sql, ...
- (FMResultSet *)executeQueryWithFormat:(NSString*)format, ...
- (FMResultSet *)executeQuery:(NSString *)sql withArgumentsInArray:(NSArray *)arguments
示例
// 查询数据
FMResultSet *rs = [db executeQuery:@"SELECT * FROM t_student"];
// 遍历结果集
while ([rs next]) {
    NSString *name = [rs stringForColumn:@"name"];
    int age = [rs intForColumn:@"age"];
    double score = [rs doubleForColumn:@"score"];

}

六、实战

（1）首先将github下载的fmdb文件夹中的文件添加到项目中，并添加libsqlite3.tbd的库引用，如下图

如果没有添加libsqlite3.tbd的话，会报如下错误

主要代码如下

//
//  ViewController.m
//  FMDBDemo
//
//  Created by 555chy on 6/22/16.
//  Copyright © 2016 555chy. All rights reserved.
//

#import "ViewController.h"
#import "fmdb/FMDB.h"
#import "fmdb/FMDatabaseAdditions.h"

@interface ViewController ()

@property FMDatabase *db;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    /*
    typedef NS_ENUM(NSUInteger, NSSearchPathDirectory) {
        NSApplicationDirectory = 1,             // supported applications (Applications)
        NSDemoApplicationDirectory,             // unsupported applications, demonstration versions (Demos)
        NSDeveloperApplicationDirectory,        // developer applications (Developer/Applications). DEPRECATED - there is no one single Developer directory.
        NSAdminApplicationDirectory,            // system and network administration applications (Administration)
        NSLibraryDirectory,                     // various documentation, support, and configuration files, resources (Library)
        NSDeveloperDirectory,                   // developer resources (Developer) DEPRECATED - there is no one single Developer directory.
        NSUserDirectory,                        // user home directories (Users)
        NSDocumentationDirectory,               // documentation (Documentation)
        NSDocumentDirectory,                    // documents (Documents)
        NSCoreServiceDirectory,                 // location of CoreServices directory (System/Library/CoreServices)
        NSAutosavedInformationDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 11,   // location of autosaved documents (Documents/Autosaved)
        NSDesktopDirectory = 12,                // location of user's desktop
        NSCachesDirectory = 13,                 // location of discardable cache files (Library/Caches)
        NSApplicationSupportDirectory = 14,     // location of application support files (plug-ins, etc) (Library/Application Support)
        NSDownloadsDirectory NS_ENUM_AVAILABLE(10_5, 2_0) = 15,              // location of the user's "Downloads" directory
        NSInputMethodsDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 16,           // input methods (Library/Input Methods)
        NSMoviesDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 17,                 // location of user's Movies directory (~/Movies)
        NSMusicDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 18,                  // location of user's Music directory (~/Music)
        NSPicturesDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 19,               // location of user's Pictures directory (~/Pictures)
        NSPrinterDescriptionDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 20,     // location of system's PPDs directory (Library/Printers/PPDs)
        NSSharedPublicDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 21,           // location of user's Public sharing directory (~/Public)
        NSPreferencePanesDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 22,        // location of the PreferencePanes directory for use with System Preferences (Library/PreferencePanes)
        NSApplicationScriptsDirectory NS_ENUM_AVAILABLE(10_8, NA) = 23,      // location of the user scripts folder for the calling application (~/Library/Application Scripts/code-signing-id)
        NSItemReplacementDirectory NS_ENUM_AVAILABLE(10_6, 4_0) = 99,	    // For use with NSFileManager's URLForDirectory:inDomain:appropriateForURL:create:error:
        NSAllApplicationsDirectory = 100,       // all directories where applications can occur
        NSAllLibrariesDirectory = 101,          // all directories where resources can occur
        NSTrashDirectory NS_ENUM_AVAILABLE(10_8, NA) = 102                   // location of Trash directory
    };
    NSSearchPathForDirectoriesInDomains一般情况下只会获得到一个目录，为了兼容多个的情况，所以返回数组
    */
    NSString *parentPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    NSString *dbPath = [parentPath stringByAppendingPathComponent:@"person.sqlite"];
    /*
     文件路径有3种情况
     (1)具体文件路径（如果不存在会自动创建）
     (2)空字符串@“”（会在临时目录创建一个空的数据库，当FMDatabase连接关闭时，数据库文件也被删除）
     (3)nil（会创建一个内存中临时数据库，当FMDatabase连接关闭时。数据库也会被销毁）
     */
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];
    if([db open]) {
        NSLog(@"database open success");
        /*
         sqlite中的基本数据类型
         （1）NULL，值是NULL
         （2）INTEGER，值是有符号整形，根据值的大小以1,2,3,4,5,6或8字节存放
         （3）REAL，值是浮点型值，以8字节IEEE浮点数存放
         （4）TEXT，值是文本字符串，使用数据库编码（UTF－8，UTF－16BE或者UTF－16LE）存放
         （5）BLOB，值是一个数据块，完全按照输入存放
         */
        bool result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS PersonTable (id integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL, age integer NOT NULL, money float NOT NULL);"];
        if(result) {
            NSLog(@"create table success");
        } else {
            NSLog(@"create table fail");
        }
    } else {
        NSLog(@"database open fail");
    }
    self.db = db;
}

-(void)insert {
    for(int i=0; i<3; i++) {
        NSString *name = [NSString stringWithFormat:@"chy_%d", arc4random_uniform(100)];
        int age = arc4random_uniform(100);
        float money = arc4random_uniform(100)/10.0f;
        BOOL result;
        //@()是将变量转化为id类型
        result = [self.db executeUpdate:@"INSERT INTO PersonTable (name, age, money) VALUES (?,?,?);", name, @(age), @(money)];
        NSLog(@"insert method 1 %@", result?@"success":@"fail");
        result = [self.db executeUpdate:@"INSERT INTO PersonTable (name, age, money) VALUES (?,?,?);" withArgumentsInArray:@[name, @(age), @(money)]];
        NSLog(@"insert method 2 %@", result?@"success":@"fail");
        result = [self.db executeUpdateWithFormat:@"INSERT INTO PersonTable (name, age, money) VALUES (%@,%d,%f);", name, age, money];
        NSLog(@"insert method 3 %@", result?@"success":@"fail");
    }
}

-(void)delete {
    /*
     在FMDB中，除查询以外的所有炒作，都称为“更新”
     create、drop、insert、update、delete等
     */
    BOOL result;
    result = [self.db executeUpdate:@"DELETE FROM PersonTable;"];
    NSLog(@"delete %@", result?@"success":@"fail");
    result = [self.db executeUpdate:@"DROP TABLE IF EXISTS PersonTable;"];
    NSLog(@"drop %@", result?@"success":@"fail");
}

-(void)query {
    int count = [self.db intForQuery:@"SELECT count(*) FROM PersonTable"];
    NSLog(@"query count = %d", count);
    FMResultSet *resultSet = [self.db executeQuery:@"SELECT * FROM PersonTable"];
    while([resultSet next]) {
        int ID = [resultSet intForColumn:@"id"];
        NSString *name = [resultSet stringForColumn:@"name"];
        int age = [resultSet intForColumn:@"age"];
        double money = [resultSet doubleForColumn:@"money"];
        NSLog(@"query %d,%@,%d,%lf", ID, name, age, money);
    }
}

/*
 touch的响应链。首先，接收touch事件的必须是用户可交互的View，也就是userInteractionEnabled属性必须是yes
 事件传递的规则是：如果上层的view截获事件，那么这个view下面的view就接收不到事件，否则触摸事件就会逐层往下传递
 */
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self insert];
    [self query];
    [self delete];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

七、运行结果