SQLiteDatabase query() 和 rawQuery() 的区别

August 11, 2014

Android

刚才在 CSDN 上看见有人问说在 Android SQLiteDatabase 里,query() 和 rawQuery() 方法的区别。对于这种问题,其实最好的办法就是参看源码,结果确实这样,通过源代码,很快就找到了问题的答案了。

咱们先看看 query() 是怎么实现的。

public Cursor query(String table, String[] columns, String selection, 
    String[] selectionArgs, String groupBy, String having, String orderBy) {
        return query(false, table, columns, selection, selectionArgs, groupBy,
                having, orderBy, null /* limit */);
}

public Cursor query(boolean distinct, String table, String[] columns,
        String selection, String[] selectionArgs, String groupBy,
        String having, String orderBy, String limit) {
    return queryWithFactory(null, distinct, table, columns, selection, selectionArgs,
            groupBy, having, orderBy, limit, null);
}

这几个方法都没有具体实现。

public Cursor queryWithFactory(CursorFactory cursorFactory,
        boolean distinct, String table, String[] columns,
        String selection, String[] selectionArgs, String groupBy,
        String having, String orderBy, String limit, CancellationSignal cancellationSignal) {
    acquireReference();
    try {
        String sql = SQLiteQueryBuilder.buildQueryString(
                distinct, table, columns, selection, groupBy, having, orderBy, limit);

        return rawQueryWithFactory(cursorFactory, sql, selectionArgs,
                findEditTable(table), cancellationSignal);
    } finally {
        releaseReference();
    }
}

最终调用的就是这个方法。

public Cursor rawQueryWithFactory(
        CursorFactory cursorFactory, String sql, String[] selectionArgs,
        String editTable, CancellationSignal cancellationSignal) {
    acquireReference();
    try {
        SQLiteCursorDriver driver = new SQLiteDirectCursorDriver(this, sql, editTable,
                cancellationSignal);
        return driver.query(cursorFactory != null ? cursorFactory : mCursorFactory,
                selectionArgs);
    } finally {
        releaseReference();
    }
}

咱们再看看 rawQuery() 是怎么实现的。

public Cursor rawQuery(String sql, String[] selectionArgs) {
    return rawQueryWithFactory(null, sql, selectionArgs, null, null);
}

还是这个方法。

public Cursor rawQueryWithFactory(
        CursorFactory cursorFactory, String sql, String[] selectionArgs,
        String editTable, CancellationSignal cancellationSignal) {
    acquireReference();
    try {
        SQLiteCursorDriver driver = new SQLiteDirectCursorDriver(this, sql, editTable,
                cancellationSignal);
        return driver.query(cursorFactory != null ? cursorFactory : mCursorFactory,
                selectionArgs);
    } finally {
        releaseReference();
    }
}

可以看到,最后,调用的都是rawQueryWithFactory(CursorFactory,String,String[],String,CancellationSignal) 这个方法,你完全可以代码都不用看懂都可以找到答案。

回到问题上,这两个方法的区别在于,最终的 SQL 语句,谁来拼?query() 做的一件事就是帮你拼写 SQL 语句,而调用 rawQuery() 是你自己拼写好语句。我认为的差别仅次而已。

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