ContentResolver query()的四個參數

public final Cursor query (Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)

Since: API Level 1

Query the given URI, returning a Cursor over the result set.

For best performance, the caller should follow these guidelines:

• Provide an explicit projection, to prevent reading data from storage that aren't going to be used.
• Use question mark parameter markers such as 'phone=?' instead of explicit values in the selection parameter, so that queries that differ only by those values will be recognized as the same for caching purposes.

Parameters

uri	The URI, using the content:// scheme, for the content to retrieve.
projection	A list of which columns to return. Passing null will return all columns, which is inefficient.
selection	A filter declaring which rows to return, formatted as an SQL WHERE clause (excluding the WHERE itself). Passing null will return all rows for the given URI.
selectionArgs	You may include ?s in selection, which will be replaced by the values from selectionArgs, in the order that they appear in the selection. The values will be bound as Strings.
sortOrder	How to order the rows, formatted as an SQL ORDER BY clause (excluding the ORDER BY itself). Passing null will use the default sort order, which may be unordered.

Returns

• A Cursor object, which is positioned before the first entry, or null

上面是2.2版本的api寫的。
解釋一下：假如一條sql語句如下：
select ＊ from anyTable where var='const'
那麼anyTable就是uri，＊就是projection，selection是“var=?"，selectionArgs寫成這樣：new String[]{'const‘｝
至於最後一個就簡單了，就是排序方式。