Question

我必须执行一个简单的查询，如：

SELECT messages.*, contacts.nick FROM messages INNER JOIN contacts ON contacts.userId = messages.userId WHERE messages.isListened=0

其中isListened被声明为INTEGER：

    "CREATE TABLE IF NOT EXISTS " + Tables.Messages.TABLE_NAME + " (" +
...
            Tables.Messages.IS_LISTENED + " INTEGER, " +
...

我无法让它发挥作用。我已经尝试过了：

        private static final String getAllMessagesSQL = 
            "SELECT "
                +Tables.Messages.TABLE_NAME+".*, "
                +Tables.Contacts.TABLE_NAME+"."+Tables.Contacts.NICK
            +" FROM "+Tables.Messages.TABLE_NAME
            +" INNER JOIN "+Tables.Contacts.TABLE_NAME
                +" ON "+Tables.Contacts.TABLE_NAME+"."+Tables.Contacts.USER_ID+" = "
                    + Tables.Messages.TABLE_NAME+"."+Tables.Messages.SENDER_USER_ID
            +" WHERE "+Tables.Messages.TABLE_NAME+"."+Tables.Messages.IS_LISTENED+"='0'";
    public void getAllMessages(final List<Message> list) {
        SQLiteDatabase db = null;
        Message message = null;
        Cursor cursor = null;

        try {
            db = dbAdapter.openToRead();
            cursor = db.rawQuery(getAllMessagesSQL, null);
            Log.w(this,"getAllMessages(): \nsql: "+getAllMessagesSQL+"\ncursor.getCount(): "+cursor.getCount());
            if (cursor.moveToFirst()){
                list.clear();
                while (!cursor.isAfterLast()) {
                    Log.w(this, "getAllMessages() message.IS_LISTENED: "+cursor.getInt(cursor.getColumnIndex(Tables.Messages.IS_LISTENED)));
                    message = getMessageFromCursor(cursor);
                    list.add(message);
                    cursor.moveToNext();
                }
            }
...

结果是：

05-26 11:06:20.706: W/DatabaseHelper(3352): getAllMessages(): 
05-26 11:06:20.706: W/DatabaseHelper(3352): sql: SELECT messages.*, contacts.nick FROM messages INNER JOIN contacts ON contacts.userId = messages.userId WHERE messages.isListened='0'
05-26 11:06:20.706: W/DatabaseHelper(3352): cursor.getCount(): 0

此外，我在没有引用0：

的情况下尝试了WHERE子句

...
    +" WHERE "+Tables.Messages.TABLE_NAME+"."+Tables.Messages.IS_LISTENED+"=0";
...

以适当的方式：

...
+" WHERE "+Tables.Messages.TABLE_NAME+"."+Tables.Messages.IS_LISTENED+"=?";
...
            cursor = db.rawQuery(getAllMessagesSQL, new String[]{"0"});

和结果是相同的 - 0记录，而我知道其中有2个为了确保我注释掉WHERE条款，如：

...                 + Tables.Messages.TABLE_NAME+"."+Tables.Messages.SENDER_USER_ID;
            //+" WHERE "+Tables.Messages.TABLE_NAME+"."+Tables.Messages.IS_LISTENED+"='0'";
....

然后我得到了以下输出：

05-26 11:12:14.046: W/DatabaseHelper(3635): getAllMessages(): 
05-26 11:12:14.046: W/DatabaseHelper(3635): sql: SELECT messages.*, contacts.nick FROM messages INNER JOIN contacts ON contacts.userId = messages.userId
05-26 11:12:14.046: W/DatabaseHelper(3635): cursor.getCount(): 2
05-26 11:12:14.046: W/DatabaseHelper(3635): getAllMessages() message.IS_LISTENED: 0
05-26 11:12:14.046: W/DatabaseHelper(3635): getAllMessages() message.IS_LISTENED: 0

因此，如果没有使用WHERE子句，可以看到有2个匹配匹配那么为什么WHERE caluse在这里不起作用？

Answer 1

尝试WHERE "+Tables.Messages.TABLE_NAME+"."+Tables.Messages.IS_LISTENED+"=0 OR " +Tables.Messages.TABLE_NAME+"."+Tables.Messages.IS_LISTENED+" IS NULL"

或更改

"CREATE TABLE IF NOT EXISTS " + Tables.Messages.TABLE_NAME + " (" +
...
            Tables.Messages.IS_LISTENED + " INTEGER NOT NULL, " +
...

使用rawQuery和WHERE子句问题的简单SQL查询

1 个答案: