What would be a good way to create a fresh sequence of serial numbers on a per-day basis in a SQL database?
Something like the auto-increment feature of integer columns in some database systems.
I'm creating/recording transactions, and the transaction is identified by the pair 'date,serial no'.
That depends on what kind of database you have. If you have access to global variables or generators, just reset it each day and use it to seed your serial number column. If not, you can store the value in a table and look it up to seed your column, again resetting it each day.
Don't forget to increment the seeds manually if necessary. (Generators are a special kind of global variable that can auto-increment themselves if set up to do so. Other variables and certainly a record in a table do not.)
To reset the value, just set a trigger on insert that checks if COUNT(DATE = today) is 0. If so, reset the value.
How about a specific table just for this purpose?
create table AvailableSerialNumbers (
AvailableOn datetime primarykey,
NextAvailableNumber int
)
You'd have to populate this in advance, but that's pretty straight-forward (make sure this is done automatically and not manually).
Note that if you have a large number of serial number records being created at the same time the create logic will bottleneck on updating the AvailbleSerialNumbers record. The easiest solution to that problem is to define multiple AvailableSerialNumbers records per day (say 100 of them) and randomly choose 1 to update. If using this approach them instead of a "NextAvailableNumber" field it should be a from/to range. When the range hits 0 delete the range record.
The best way is to use the date as part of the number, such as having 080216001 through 080216999 for today. Can you have non-contiguous numbers?
Related
The column auto-increments. User wants to insert a row with a specific number (I've confirmed it doesn't already exist in the column). In SQL Server I'd do a quick SET IDENTITY_INSERT ON and insert statement. Is there a way to this for Microsoft Access or are they just out of luck.
Can run an INSERT action SQL.
But then need to Compact & Repair to reset the autonumber seed. Or, per #4dmonster comment, run another INSERT with the maximum autonumber value already in database. As long as the autonumber is set for unique index, the insert will fail but sequence will be fixed and normal data entry will generate next number. I tested and it worked.
I can only guess this autonumber is used as a sequential number that must be accounted for, as in a license number series. Otherwise, sequence gaps should not be a concern and can be ignored.
NotAn answer, but a workaround. Don't make the column autoincrement, but set the default value to max current values plus one. The defualt will, in effect, step up by one, but the user can pick a different value. Has not been tested on very large tables.
I am in the situation where multiple user inserting values from application to database via web service, have using stored procedure for validate and insert records.
Requirement is create unique number for each entries but strictly in SEQUENCE only. I added Identity column but its missed some of the number in between e.g. 25,26,27,29,34...
Our requirement is strictly generate next number only like we use for Invoice Number/ Order Number/ Receipt Number etc. 1,2,3,4,5...
I checked below link about Sequence Number but not sure if its surely resolve my issue. Can someone please assist in this.
Sequence Numbers
If you absolutely, positively cannot have gaps, then you need to use a trigger and your own logic. This puts a lot of overhead into inserts, but it is the only guarantee.
Basically, the parts of a database that protect the data get in the way of doing what you want. If a transaction uses a sequence number (or identity) and it is later rolled back, then what happens to the generated number? Well, that is one way that gaps appear.
Of course, you will have to figure out what to do in that case. I would just go for an identity column and work on educating users that gaps are possible. After all, if you don't want gaps on output, then row_number() is available to re-assign numbers.
I'm currently working on my first application that uses a database so I'm very new to this. The database has multiple tables that are what you would expect to normally see.
However, I created one table which only has one row and one column used to keep a count of the total items processed by the program so it's available to access elsewhere. I can't just use
SELECT COUNT(*) FROM table_name
because these items that I am processing I do not want to actually keep in a table.
It seems like a waste to use a table to store one value so I am wondering if there a better way to keep track of this value.
What is your table storing? it's storing some kind of processing audit. So make it a little more useful - add a column storing the last datetime that the data was processed. Add a column for the time it took to process. Add another column which stores the username (or some identifier) of whoever ran the process. Now add a row for every table that is processed (there's only one now but there might be more in future). Try and envisage how your processing is going to grow in future
Whats the best way to implement a unique counter generator in SQL Server 2005?
So I have a single field in a table with a single value which is the counter.
I want to get the current value and also increment by 1.
So database will hold the next incremented value. I have tried several select + update combos but since this counter is being hit very hard (probably 5000 times per minute) from various calls from independent applications, the application seems to be slow. How can I get a better counter?
I need the value to be serial so we cannot have a different table for each application.
I have suggestion from someone here: http://www.sqlines.com/mysql/how-to/select-update-single-statement-race-condition but not sure it is right or may have other issues.
Can you not just Insert a row into a table using an Identity column? Once you retrieve the inserted counter value using SCOPE_IDENTITY, you'll know what the previous version was. It'll be fast because it's not checking existing rows. If you don't need to store per-request rows, you could clear these out occasionally.
I'd like to take a table, generate it's hash string, store it, then compare it at a later predefined time and see if it matches, if not take note of the modification time and store that with the new change date.
This is because I believe an on insert trigger would cause a bad slow down if a batch of over 5000+ insert statements is submitted. I move large amounts of data per day and other than having a column of smalldatetime with a default get date, I have certain tables I do not have permissions to change the schema of, so I don't have a way to determine the last changed date of.
You can use CHECKSUM on various fields to do this.