1. Generate Surrogate Key In Sql Tutorial
2. Generate Surrogate Key In Sql Server
3. How To Generate Surrogate Key In Sql

In a current database, the surrogate key can be the primary key, generated by the database management system and not derived from any application data in the database. The only significance of the surrogate key is to act as the primary key. Surrogate keys can be generated in a variety of ways, and most databases offer ways to generate surrogate keys. For example, Oracle uses SEQUENCE, MySQL uses AUTOINCREMENT, and SQL Server uses IDENTITY. Sep 13, 2009  13 September 2009. Identity over-use: Surrogate vs Composite keys in SQL Server. The SQL Server ‘Identity’ column is a handy way of ensuring a unique primary key, but I have noticed a tendency for some database designs to over-use it.

A surrogate key is an auto generated value, usually integer, in the dimension table. It is made the primary key of the table and is used to join a dimension to a fact table. Among other benefits, surrogate keys allow you to maintain history in a dimension table. Despite of the their popularity, SSIS doesn’t have a built in solution for generating surrogate keys. Let’s take a look at a few alternatives in this post.

• Surrogate Key Overview. A surrogate key is a system generated (could be GUID, sequence, etc.) value with no business meaning that is used to uniquely identify a record in a table. The key itself could be made up of one or multiple columns. The following diagram shows an example of a table with a surrogate key (AddressID column) along with some sample data.
• A Surrogate Key can be implemented by an auto-incremented key. SQL Server supports an IDENTITY column to perform the auto-increment feature. It allows a unique number to be generated when a new record is inserted into the database table.Syntax for Introducing Auto identity column with Create Table.
• A surrogate key on a table is a column with a unique identifier for each row. The key is not generated from the table data. Data modelers like to create surrogate keys on their tables when they design data warehouse models. You can use the IDENTITY property to achieve this goal simply and effectively without affecting load performance.
• How do I create a surrogate key on a database with composite foreign keys? Ask Question Asked 7. Which is now a surrogate key rather than a composite foreign key? Is there an easy way to do this as a SQL command? Share improve this question. Asked Jul 3 '12 at. How do i create a Parent surrogate key that corresponds to the.

First, create the following table. We will import data from Person.Person table (AdventureWorks sample) into this table. Note PersonSK is the surrogate key.
CREATE TABLE [dbo].Person
(
[PersonSK] INT IDENTITY(1,1) NOT NULL
, [FirstName] NVARCHAR(50) NULL
, [LastName] NVARCHAR(50) NULL
, CONSTRAINT PK_PersonSK PRIMARY KEY [PersonSK]
) ;

With IDENTITY()

Drag a data flow task on to the control flow and configure the OLE DB source.

Generate Surrogate Key In Sql Tutorial

Next, drag OLE DB destination and connect it to the source. Specify the connection manager, and choose Table or view – fast load as the data access mode. This performs a bulk insert and is the fastest of all.

Destination table has three columns, but source has only two columns. In the mappings page, map input and output columns for FirstName and LastName and ignore the mapping for PersonSK.

When you run the package, becasue PersonSK is an identity column in the table, SQL Server will automatically generate values for you. This solution is easy and fast, but sometimes depending on your ETL methodology, you can’t rely on IDENTITY().

With Script Component

I frequently use Script Transformation. The steps are nicely written in this post by Phil Brammer (b). This is simply a script used as a transformation. The script generates a row number for each row passed through the data flow.

With ROW_NUMBER()

SSIS (data flow) engine generated the new row number when using script transformation. Instead, you can use ROW_NUMBER() when working with SQL Server data source to let the database engine do the work for you. This can be faster.

If you’re doing an incremental load, first find the maximum key value from the destination. I’ll use the following query. It’ll return zero if there were no rows, else it returns the maximum value.

SELECT ISNULL(MAX(PersonSK),0) SK
FROM dbo.Person

Add an Execute SQL Task to the control flow and set the result property to single row. Then, add a variable to hold the return value.

Next, connect a data flow task to the execute sql task. We will use the following SQL statement in the OLE DB source editor. In addition to the LastName and FirstName columns, we are using ROW_NUMBER() function to generate a unique number for every row.

SELECT
ROW_NUMBER() OVER(ORDER BY [LastName]) SK
, [LastName]
, [FirstName]
FROM
Person.Person


The query will generate numbers starting from 1 for each row, but while loading to destination we don’t want to start from 1. We want to find the maximum value in the destination and start from the next highest value. So, I’m adding the max value to every row number using parameters in the OLE DB source.

In the OLE DB destination, check the box that says Keep Identity. Steam key generator no survey no password 2017 free. By do this we are asking SSIS to keep the identity values that are generated by the source. In the mappings page, you’ll see a new input that was created in the OLE DB source. Map it to PersonSK surrogate key. Git bash generate ssh key for github download.

Generate Surrogate Key In Sql Server

Go ahead and run the package. If it’s all good you will see cute little green tick marks like below.

Summary

How To Generate Surrogate Key In Sql

In this example, we looked at different options to generate surrogate keys while loading dimensions using SSIS. We used IDENTITY() constraint in SQL Server. We talked about Script Component. Finally, we saw making use ROW_NUMBER() function. Last option is twice as fast as using the Script Component with around 20,000 rows and an index on LastName column.