Question

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

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

What is the expected result?

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?

Answer 1

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` = ?

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

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

To quote:

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