使用fmdb进行SQLlite 操作

ARC还是手工管理内存

在你的cocoa项目中，可以任意地使用，fmd在编译选项中判断作出正确的选择

Usage

There are three main classes in FMDB:

1. FMDatabase - Represents a single SQLite database. Used for executing SQL statements.
2. FMResultSet - Represents the results of executing a query on an FMDatabase.
3. FMDatabaseQueue - If you're wanting to perform queries and updates on multiple threads, you'll want to use this class. It's described in the "Thread Safety" section below.

使用方面很简单，三个东西FMDatabase从数据库层考虑，可以作为SQL command的执行体；Resultset是执行结果集合，Queue，表明多线程执行使用；数据库的创建也可以以三个方式，第一文件，第二就是临时文件，最后一个是内存

Database Creation

An FMDatabase is created with a path to a SQLite database file. This path can be one of these three:

1. A file system path. The file does not have to exist on disk. If it does not exist, it is created for you.
2. An empty string (@""). An empty database is created at a temporary location. This database is deleted with the FMDatabaseconnection is closed.
3. NULL. An in-memory database is created. This database will be destroyed with the FMDatabase connection is closed.

涉及到具体操作，例如执行更新（非Select），包括CREATE, PRAGMA, UPDATE,INSERT, ALTER, COMMIT, BEGIN, DETACH, DELETE, DROP, END, EXPLAIN, VACUUM

这些函数的返回是一个BOOL，如果是NO。检查更多NSError的信息

对于Select，就需要用Resultset去接收返回的records：

FMResultSet *s = [db executeQuery:@"SELECT * FROM myTable"];while ([s next]) {    //retrieve values for each record}

语法看起来也很简单，遍历，然后获取每行中各字段的值（有一大堆方法／体力活）：

• intForColumn:
• longForColumn:
• longLongIntForColumn:
• boolForColumn:
• doubleForColumn:
• stringForColumn:
• dateForColumn:
• dataForColumn:
• dataNoCopyForColumn:
• UTF8StringForColumnIndex:
• objectForColumn:

使用示范代码：

- (IBAction)doButton:(id)sender {    NSFileManager* fm = [[NSFileManager alloc] init];    NSString* docsdir = [NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES) lastObject];    NSString* dbpath = [docsdir stringByAppendingPathComponent:@"people.db"];        [fm removeItemAtPath:dbpath error:nil]; // in case we already did this once        FMDatabase* db = [FMDatabase databaseWithPath:dbpath];    if (![db open]) {        NSLog(@"Ooops");        return;    }    [db executeUpdate:@"create table people (lastname text, firstname text)"];        [db beginTransaction];    [db executeUpdate:@"insert into people (firstname, lastname) values ('Matt', 'Neuburg')"];    [db executeUpdate:@"insert into people (firstname, lastname) values ('Snidely', 'Whiplash')"];    [db executeUpdate:@"insert into people (firstname, lastname) values ('Dudley', 'Doright')"];    [db commit];        NSLog(@"I think I created it");    [db close];}- (IBAction)doButton2:(id)sender {    NSString* docsdir = [NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES) lastObject];    NSString* dbpath = [docsdir stringByAppendingPathComponent:@"people.db"];        FMDatabase* db = [FMDatabase databaseWithPath:dbpath];    if (![db open]) {        NSLog(@"Ooops");        return;    }        FMResultSet *rs = [db executeQuery:@"select * from people"];    while ([rs next]) {        NSLog(@"%@ %@", [rs stringForColumn:@"firstname"], [rs stringForColumn:@"lastname"]);    }        [db close];}

感谢This is an Objective-C wrapper around SQLite: http://sqlite.org/：

https://github.com/ccgus/fmdb