Is there a generic way to get sequence

Question

Hey,
I need a counter that will not initialized when my sever restarted, so i decide to write sequence in the data base for this.
My question is there a generic (for any vendor) way to get next id?
Thank you

Answer 1

If all of the target databases supports transactions then it is possible
1. Create a table that holds sequence number
2. For each operation
....a. Start transaction
....b. Get row - only one exists. Hold unto value.
....c. Increment value
....d. Update row
....e. Commit transaction.
....f. Return value from step b.
3. Use index value in some other expression.
Some databases, with non-ANSI SQL code might allow step 2 to be handled as a single statement, thus no transaction is needed.
The above allows for sequential values.
You can find "guid" algorithms written in java. Those produce non-sequential values.
You can produce your own value that is sequential if you can make assumptions about the enviroment that all of the systems will be running in by combining some or all of the following values.
- datetime
- ip
- process id
- static counter in application
- thread id