这几天连续加班，昨天很早就睡了。一个人的时候要学会自我祝福，祝自己注意身体，天天精力充沛。明天父亲生日，在此祝父亲生日快乐，身体健康，笑口常开。

接着介绍android系统短彩信数据库设计。

单例模式，获取数据库设计类的单一引用。

关于数据模式，可以参考：http://blog.csdn.net/hailushijie/article/details/8715154。

1、

/**
     * Return a singleton helper for the combined MMS and SMS
     * database.
     */
    /* package */ static synchronized MmsSmsDatabaseHelper getInstance(Context context) {
        if (sInstance == null) {
            sInstance = new MmsSmsDatabaseHelper(context);
        }
        return sInstance;
    }

2、

static final String DATABASE_NAME = "mmssms.db";
    static final int DATABASE_VERSION = 55;
    private final Context mContext;
    private LowStorageMonitor mLowStorageMonitor;


    private MmsSmsDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);

        mContext = context;
    }

3、

public static void updateThread(SQLiteDatabase db, long thread_id) {
        if (thread_id < 0) {
            updateAllThreads(db, null, null);
            return;
        }

        // Delete the row for this thread in the threads table if
        // there are no more messages attached to it in either
        // the sms or pdu tables.
        int rows = db.delete("threads",
                  "_id = ? AND _id NOT IN" +
                  "          (SELECT thread_id FROM sms " +
                  "           UNION SELECT thread_id FROM pdu)",
                  new String[] { String.valueOf(thread_id) });
        if (rows > 0) {
            // If this deleted a row, let's remove orphaned canonical_addresses and get outta here
            db.delete("canonical_addresses",
                    "_id NOT IN (SELECT DISTINCT recipient_ids FROM threads)", null);
            return;
        }
        // Update the message count in the threads table as the sum
        // of all messages in both the sms and pdu tables.
        db.execSQL(
            "  UPDATE threads SET message_count = " +
            "     (SELECT COUNT(sms._id) FROM sms LEFT JOIN threads " +
            "      ON threads._id = " + Sms.THREAD_ID +
            "      WHERE " + Sms.THREAD_ID + " = " + thread_id +
            "        AND sms." + Sms.TYPE + " != 3) + " +
            "     (SELECT COUNT(pdu._id) FROM pdu LEFT JOIN threads " +
            "      ON threads._id = " + Mms.THREAD_ID +
            "      WHERE " + Mms.THREAD_ID + " = " + thread_id +
            "        AND (m_type=132 OR m_type=130 OR m_type=128)" +
            "        AND " + Mms.MESSAGE_BOX + " != 3) " +
            "  WHERE threads._id = " + thread_id + ";");

        // Update the date and the snippet (and its character set) in
        // the threads table to be that of the most recent message in
        // the thread.
        db.execSQL(
            "  UPDATE threads" +
            "  SET" +
            "  date =" +
            "    (SELECT date FROM" +
            "        (SELECT date * 1000 AS date, thread_id FROM pdu" +
            "         UNION SELECT date, thread_id FROM sms)" +
            "     WHERE thread_id = " + thread_id + " ORDER BY date DESC LIMIT 1)," +
            "  snippet =" +
            "    (SELECT snippet FROM" +
            "        (SELECT date * 1000 AS date, sub AS snippet, thread_id FROM pdu" +
            "         UNION SELECT date, body AS snippet, thread_id FROM sms)" +