SQLite是一款輕量級的關系型數據庫。無需服務進程，無需安裝和配置，支持事務處理。它的運算速度快，占用資源少，適合在存儲大量復雜的關系型數據的時候使用。

一、SQLite數據庫使用

（1）使用幫助類SQLiteOpenHelper創建數據庫

• SQLiteOpenHelper是SQLiteDatabase的幫助類， 用于管理數據庫的創建和升級。
• 自定義幫助類繼承SQLiteOpenHelper，并重寫onCreate()和 onUpgrade()，分別在這兩個方法中去實現創建、升級數據庫的邏輯。
• 調用幫助類對象的getReadableDatabase() 和getWritableDatabase()去創建或打開一個現有的數據庫，并返回一個可對數據庫操作的SQLiteDatabase。
• 在onCreate方法中調用SQLiteDatabase的方法execSQL()創建數據庫。execSQL()可以接受和處理SQL語句。

public class MySQLiteHelper extends SQLiteOpenHelper {
    public static final String CREATE_MEMBER = "create table member(id integer primary key autoincrement, name text, sex text, age integer)";
    public static final String CREATE_INTEREST = "create table interest(id integer primary key autoincrement,content text)";
    public static final String CREATE_MEMBER_AGE = "alter table member add column age integer";

    public MySQLiteHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //創建member表
        db.execSQL(CREATE_MEMBER);
        //創建interest表
        db.execSQL(CREATE_INTEREST);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        switch (oldVersion) {
            case 1:
                //升級數據庫增加表
                db.execSQL(CREATE_INTEREST);
            case 2:
                //升級數據庫增加表中字段age
                db.execSQL(CREATE_MEMBER_AGE);
                break;
            default:
        }
    }
}

（2）操作數據表

    //獲取到SQLiteDatabase的實例
    SQLiteOpenHelper dbHelper = new MySQLiteHelper(this, "demo.db", null, 1);
    
    private void insert() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("name", "黃渤");
        values.put("sex", "男");
        values.put("age", 34);
        db.insert("member", null, values);
        values.clear();

        db.execSQL("insert into member(name,sex,age) values('黃渤','男',34)");
    }

    private void update() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("name", "岳云鵬");
        db.update("member", values, "id = ?", new String[]{"1"});
        values.clear();

        db.execSQL("update member SET id = '1' WHERE name = '岳云鵬'");
    }

    private void delete() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        db.delete("member", "name= ?", new String[]{"岳云鵬"});

        db.execSQL("delete from member where name = '岳云鵬'");
    }

    @SuppressLint("Recycle")
    private void rawQuery() {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        //查詢member表中所有數據
        Cursor cursor1 = db.query("member", null, null, null, null, null, null);
        //查詢member表中年齡大于30的數據
        Cursor cursor2 = db.query("member", null, "age > ?", new String[]{"30"}, null, null, null);

        Cursor cursor3 = db.rawQuery("select * from member", null);

        //從Cursor對象中取出數據
        List<Member> memberList = new ArrayList<Member>();
        if (cursor1 != null && cursor1.moveToFirst()) {
            do {
                int id = cursor1.getInt(cursor1.getColumnIndex("id"));
                String name= cursor1.getString(cursor1.getColumnIndex("name"));
                String sex= cursor1.getString(cursor1.getColumnIndex("sex"));
                int age= cursor1.getInt(cursor1.getColumnIndex("age"));
                Member member = new Member();
                member.setId(id);
                member.setName(name);
                member.setSex(sex);
                member.setAge(age);
                memberList.add(member);
            } while (cursor1.moveToNext());
        }
    }

SQLite源碼解析