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Increment ID on insertion of a new row on database

I need something which I dont know if it's possible to achieve. Basically I'll be adding new rows of information from java to a database with the table structure , ex:
Number | Color | Size
0 | Red | Big
1 | Green | Small
2 | Yellow| Medium
I'm using java and I'll only input the Color and Size, and I would like to know if it's possible to create a trigger that will store the variable Number(id) on the database side, and increment it each time I do an Insert of a new row into the db. I was thinking doing something like, " INSERT INTO table ((null),'Red', 'Big'), and then the database would update the value with the proper Number.
Also should be possible to bare with fact that some rows can be deleted, but it won'shouldn't affect anything, example: if I have ID's 0 , 1 ,2 and I delete 1, next row should still be 3.
Another thing, I'm using Sybase SQL Anywhere 12 to do this.

You should use autoincrement column in your database.
See this.
http://www.sqlines.com/sybase-asa/autoincrement_identity

As #Gordon Linoff said ...
Identity columns are doing that, for example ...
create table T1 (ID int identity(1,1), Name nvarchar(100))
In this case you would go ...
insert into T1 (Name) values ('John')
So, you would insert Name 'John' and DB itself would give him ID 1
Next time you do insert, ID 2 would be set ... and so on and on ..
Identity(1,1) - it means start from 1 and increment it by 1 on new insert
Thing about this is that once number is taken, there is no going back, so if you have IDs 1, 2, 3 .. and delete ID 3 .. on next insert ID will go up to 4, it will not populate "missing number"

there are several solutions that satisfy your requirements but those are different in several aspects and you should decide to select the best one.
some solutions are exists in DB context. (for example #Gregory answer),
but some other solutions are independent of the DB type and specific features. it means that you implement your solution independent of your db type and you could change your db (oracle, sql-server, my-sql , ...) and there is no need to change your java code.
in jpa there are three Sequence Strategies to solving this problem with #GeneratedValue.
1) Table sequencing: you use a separate table for this purpose in your db. this table hold the proper ids for other tables that have auto-increment-columns with this strategy.
2) Sequence objects: you use a sequence object in your db and jpa handle it. Sequence objects are only supported in some databases, such as Oracle, DB2, and Postgres.
3) Identity sequencing: uses special IDENTITY columns in the database to allow the database to automatically assign an id to the object when its row is inserted. Identity columns are supported in many databases, such as MySQL, DB2, SQL Server, Sybase, and PostgreSQL. Oracle does not support IDENTITY columns but it is possible to simulate them using sequence objects and triggers.
if you want to be independent from your db type, I recommend you to use "table strategy" in jpa.
see Java Persistence/Identity and Sequencing for details.
you asked:
I would like to know if it's possible to create a trigger that will
store the variable Number(id) on the database side, and increment it
each time I do an Insert of a new row into the db.
yes, you could use trigger, but as i mentioned there are some simpler solutions rather it.
Also should be possible to bare with fact that some rows can be
deleted, but it won'shouldn't affect anything
in jpa solutions the deleted ids don't be used in next usage, but if you implement your own solution you could use them.
I hope this answer help you.

Getting next ID as PK for table insert

I'm working on some old java code, and as part of an insert, the code makes a db call to get the last ID used in a table, then increments the ID, and uses the incremented ID as the next ID to use for the insert, as the PK.
It's a web application, and it seems to me that the same ID could be retrieved on a subsequent get ID call before the first/prior insert is done.
How would I prevent this, to ensure that the same ID is not reused?

Use a transaction in your sql code.

If you Database Server supports the Auto Increment attribute, then you can apply it to the ID column and it will assign itself incrementing unique IDs. The server does all the work and ensures that the ID is valid and unique.

Refreshing PrimaryID to start from one after a deleted Row

Im programming a program in java and i have a database in a JTable just like the ones below. I wanted to know if it is possible to refresh the primaryID location from 1 on the GUI interface form one when a row is deleted? for example below the LoactionID is deleted for London and added again with an id 4. Is this possible?
Im using SQL in java

To answer your question, yes it is possible.
There is no good reason for you to do this though, and I highly recommend you don't do this.
The only reason to do this would be for cosmetic ones - the database doesn't care if records are sequential, only that they relate to one another consistently. There's no need to "correct" the values for the database's sake.
If you use these Id's for some kind of numbering on the UI (cosmetic reason):
Do not use your identity for this. Separate the visual row number, order or anything else from the internal database key.
If you REALLY want to do this,
Google "reseeding or resetting auto increment primary ID's" for your sql product.
Be aware for some solutions if you reset the identity seed below values that you currently have in the table, that you will violate the indentity column's uniqueness constraint as soon as the values start to overlap
Thanks Andriy for mentioning my blindly pasting a mysql solution :)
Some examples:
ALTER TABLE table_name ALTER COLUMN auto_increment_column_name RESTART WITH 8 Java DB
DBCC CHECKIDENT (mytable, RESEED, 0)
Altering the sequence

Getting timestamp of last insert in mysql along with primary key in a single query?

I tried searching for the solution to this problem but am still stuck. Seems rather simple (or maybe it's my ignorance :)
I already fetch the 'auto incremented' primary key after inserting. My question is can I retrieve the timestamp of the last insert WITHOUT sending a second query of SELECT m.timestamp from My_Table m where id = 123; //i.e., 123 is the id of the row that was just created
It seems wasteful to go back and forth but is that really the way to do it?
I'm using Spring's JDBCTemplate to query the MySQL DB.

What is important is getting the last inserted id. Check this
http://dev.mysql.com/doc/refman/5.0/en/getting-unique-id.html
Sometimes, there is no easy way.

How can I treat a sequence value like a generated key?

Here is my situation and my constraints:
I am using Java 5, JDBC, and DB2 9.5
My database table contains a BIGINT value which represents the primary key. For various reasons that are too complicated to go into here, the way I insert records into the table is by executing an insert against a VIEW; an INSTEAD OF trigger retrieves the NEXT_VAL from a SEQUENCE and performs the INSERT into the target table.
I can change the triggers, but I cannot change the underlying table or the general approach of inserting through the view.
I want to retrieve the sequence value from JDBC as if it were a generated key.
Question: How can I get access to the value pulled from the SEQUENCE. Is there some message I can fire within DB2 to float this sequence value back to the JDBC driver?
Resolution:
I resorted to retrieving the PREVIOUS_VAL from the sequence in a separate JDBC call.

Have you looked at java.sql.Statement.getGeneratedKeys()? I wouldn't hold out much hope since you're doing something so unusual but you never know.

You should be able to do this using the FINAL TABLE syntax:
select * from final table (insert into yourview values (...) );
This will return the data after all triggers have been fired.