Retrieving the null value from Sqlite database in android

Question

Guys i have stored a null value in the column of sqlite database

the value that is storing is return "null"

Now using following code to retrieve it

int i = resultSet.getInt(resultSet.getColumnIndex(columnName));
String str = resultSet.getString(resultSet.getColumnIndex(columnName));
boolean bool = resultSet.isNull(resultSet.getColumnIndex(columnName));

if( str == null ) {
    return -1;
}            
return i;

The debugger shows the value of str = "null"

but this condition is not working with str == null , str == "" , str == "null"

anyone can give me a hit of what to do..

Also resultset.isNull gives me a value of false.

So how can i store null in database, secondly if i use "null" then how can i make this condition work.

Plz add the code where you are adding null value to database. — Saurabh Pareek
– Saurabh Pareek, Commented Feb 7, 2012 at 5:20

Kal · Accepted Answer · 2012-02-07 05:20:38Z

7

If you have stored the "null" literal string in the database, you compare against it like so --

if ( "null".equals(str) )

To store a null value in your database table, you use PreparedStatement.setNull()

answered Feb 7, 2012 at 5:20

Kal

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3 Comments

Muhammad Umar Over a year ago

can u give an idea of how can i use these preparedStatement? any small example

Kal Over a year ago

PreparedStatment might be overkill. You can probably just use sqlitedb.execSQL("insert into yourtable values(null, ...");

Muhammad Umar Over a year ago

mDb.execSQL(updateQuery, valVars); USING this and null as one of the arguments stored in valVar but it gives error of null pointer exception

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Also resultset.isNull gives me a value of false.

resultset.isNull will give true if your your value = null. But as you said your value = "null" , which is a String.

The debugger shows the value of str = "null"

but this condition is not working with str == null , str == "" , str == "null"

try comparing with str.equals("null")

mDb.execSQL(updateQuery, valVars); USING this and null as one of the arguments stored in valVar but it gives error of null pointer exception

As sepcified on http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html this method should be used to - Execute a single SQL statement that is NOT a SELECT/INSERT/UPDATE/DELETE.

Please try using update(String table, ContentValues values, String whereClause, String[] whereArgs) or updateWithOnConflict(String table, ContentValues values, String whereClause, String[] whereArgs, int conflictAlgorithm). Also please cross verify that your field in db allows NULL(i.e. Not Null = 0)

hope this helps :)

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Feb 7, 2012 at 7:13

Chanchal Shelar

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1 Comment

Muhammad Umar Over a year ago

actually i need to run sql statements and using Update and others i can't use sql statements...

Unicusand · Accepted Answer · 2012-02-07 05:20:10Z

-1

Check for String length.like,

if(str.length == 0){ }

answered Feb 7, 2012 at 5:20

Unicusand

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2 Comments

Unicusand Over a year ago

yes you right .But if nothing in string means length is zero right?

Matthew Flaschen Over a year ago

No one discussed "nothing in string".

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