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iOS/SQLite

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  1. iOS/SQLite CS328 Dick Steflik

  2. Embedded Databases • SQLite is the embedded database of choice for both the iOS and Android mobile platforms • SQLite is called an embedded database because its primary use is to provide data persistence to your app, it is an integral part of your app. • Apps do not share Embedded Databases the way they share databases like Oracle and DB2.

  3. Application Access to SQLite • Core Data • an Apple provided Object-Relational Mapping framework • stores Objective-C objects into a SQLite Database • object instance data looks like a row in an SQL table. • Flying Meat Database (FMDB) • FMDB is a set of Objective C wrappers for SQLite • let you program using embedded SQL • modeled after Java JDBC

  4. Core Data • Benefits • supported by Apple • don't need to know SQL • Drawbacks • does not work with RDBMS as the store • ordered relationships are hard • undo/rollback doesn't always work • data migration to a revised model is hard

  5. FMDB • Two main classes: • FMDatabase • represents a single SQLite database, used for executing SQL statements • FMResultSet • represents the results of executing a query on an FMDataBase

  6. Database Creation • Persistent and temporary databases can be created • Permanent at some file system path:FMDatabase * mydb = [FMDatabase databaseWithPath:@"/var/mydb.db"]; • Empty database at a temp location, database is deleted when it is closed:FMDatabase * mydb = [FMDatabase databaseWithPath:@""]; • In memory database created destroyed when database connection is closed: • FMDatabase * mydb = [FMDatabase databaseWithPath:NULL];

  7. Opening the Database • before you can use the database it must be opened. if (![db open]) { [db release]; return;} • fails – insufficient resources, permissions

  8. Closing the Database • Close the FMDatabase connection when you are done with it. SQLite will then relinquish and resources it has acquired.[db close]

  9. Executing Updates • [FMDatabase executeUpdate] • use this method to execute all SQL statements except SELECT. • returns a bool, yes is a good return, no is not • Ex[db executeUpdate:@"INSERT INTO mytable VALUES ( ?)"]

  10. Select • [FMDatabase executeQuery] • Query results come back in an FMResultSet • ExFMResultSet * s = [db executeQuery:@"SELECT * FROM mytable"];while ([s next]) { // retrieve the values}

  11. sqlite3.h • This .h file is on your MAC where you installed SQLite, it is the C language interface to SQLite. It can be used in place of FMDB. • The documentation in sqlite3.h is excellent.

  12. FMResultSet data retrieval • intForColumn • longForColumn • longLongIntForColumn • boolForColumn • doubleForColumn • stringForColumn • dateForColumn • dataForColumn • dataNoCopyForColumn • UTF8StringForColumnIndex • objectForColumn

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