How to get the next identity value from SQL Server

Question

I need to get the next identity value from SQL Server.

I use this code :

SELECT IDENT_CURRENT(\'table_name\') + 1

This

Answer 1

I tend to agree with other posters that this is not the right way to do this, however it can be convenient for certain cases. Several posts asks why at all do this, and let me give you an example where it was convenient for me, and how and why.

I'm implementing a Bitcoin node. I want the blockchain stored in an SQL database. Every block is received from the network from other nodes and miners. The details you can find elsewhere.

When receiving a block it contains one header, any number of transactions and each transaction any number of inputs and outputs. I have 4 tables in my database - you guessed it - a header table, transaction table, inputs table and outputs table. Each row in the transaction, inputs and outputs table are linked with IDs to eachother up into the header row.

Some blocks contain several thousand transactions. Some transactions hundres of inputs and/or outputs. I need them stored in the DB from a convenient call in C# without compromising integrity (the IDs all link up) and with decent performance - which I cannot get by committing row by row when there are close to 10000 commits.

Instead, I make absolutely sure to sync-lock my database object in C# during the operation (and I don't have to worry about other processes accessing the database also), so I can conveniently do a IDENT_CURRENT on all 4 tables, return the values from a stored proc, fill up the nearly 10000 rows in 4 List while incrementing the IDs and call the SqlBulkCopy.WriteToServer method with option SqlBulkCopyOptions.KeepIdentity set, and then send it all in 4 simple calls, one for each tableset.

The performance gain (on a 4-5 years old mid-range laptop) was going from about 60-90 seconds down to 2-3 seconds for the really large blocks, so I was happy to learn about IDENT_CURRENT().

The solution might not be elegant, might not be by the book so to speak, but it is convenient and simple. There are also other ways to accomplish this, I know, but this was just straight forward and took a few hours to implement. Just make sure you don't have concurrency issues.