Android的SQLite的查询在选择问号，并在selectionArgs两个空 [英] Android SQLite query has question mark in selector and null in selectionArgs

问题描述

在安卓如果我叫像下面的SQLiteDatabase方式查询：

In android if I call the SQLiteDatabase method query like the following:

sqlitedb.query("mytable", null, "name = ?",
     new String[] {null}, null, null, null);

什么是预期的结果？

What is the expected result?

我所期望的 NullPointerException异常但似乎我越来越似乎有相同的数据，因为我执行的最后一个非空selectionArgs两个查询上的游标回来。这是预期的行为，我想我必须做我自己的空检查调用此方法前，而是通过名称为空，以得到正确的结果？

I would expect a NullPointerException but it seems like I am getting a cursor back that seems to have the same data as the last non-null selectionArgs query I performed. Is this expected behavior, I guess I have to do my own null checking before calling this method and instead pass "name IS NULL" to get the correct result?

推荐答案

这无关与NPE @ satur9nine。它与SQL参数procressing做。我已经验证你是正确的。使用SQLite，如果您发出：

This has nothing to do with NPE @satur9nine. It has to do with SQL argument procressing. I've verified that you are correct. With SQLite, if you issue:

SELECT * FROM `mytable ` WHERE `name` = ?

跨越其与空名称字段行的表空的说法，你会得到任何结果。你将不得不发出查询：

with a null argument across a table which has rows with null name fields, you will get no results. You are going to have to issue the query:

SELECT * FROM `mytable ` WHERE `name` IS NULL

这不仅是Android的，而且JDBC。这是一个数据库的问题。 SQLite的，H2和MySQL中的所有行为这种方式。从这个伟大的SQL教程：

This is not just Android but also JDBC. It is a database issue. SQLite, H2, and MySQL all behave this way. From this great SQL tutorial:

http://www.w3schools.com/sql/sql_null_values​​.asp

要报价：

这是不可能的，以测试NULL值与比较运算符，如=，＆所述;或＆所述;>

It is not possible to test for NULL values with comparison operators, such as =, <, or <>.

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