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Assign Surrogate keys to the dimension tables where the dimensions are generated in a source system and loaded into SQL DW (or APS). Extract dimension values from the fact table and assign surrogate keys when the loaded data is such that a single record set has both fact and dimension values. Since surrogate keys are used to uniquely identify rows, their values are normally displayed prominently on all forms and reports for the users to see. F The use of surrogate keys usually complicates application programming since most DBMS products require the application program to generate surrogate key values.

• To Generate A Surrogate Key Microsoft Access Uses A
• To Generate A Surrogate Key Microsoft Office
• To Generate A Surrogate Key Microsoft Email
• To Generate A Surrogate Key Microsoft Account
• Surrogate Key Definition

APPLIES TO: Azure Data Factory Azure Synapse Analytics (Preview)

Microsoft SQL Server 2012 provides many ways to create a surrogate key. Two of the solutions are identify keys and sequences. Introduction to Identity Columns. One of the goals of a good table is to be able to uniquely identity each record. In most cases, the database engine should not confuse two records. Dec 23, 2019  A Sequence is a named object in an individual Snowflake schema and database. These sequences are used to generate unique numbers. You can use sequence to generate unique numbers that can be used as surrogate key values for primary key values.

Use the surrogate key transformation to add an incrementing key value to each row of data. This is useful when designing dimension tables in a star schema analytical data model. In a star schema, each member in your dimension tables requires a unique key that is a non-business key.

Configuration

Key column: The name of the generated surrogate key column.

Start value: The lowest key value that will be generated.

Increment keys from existing sources

To start your sequence from a value that exists in a source, use a derived column transformation following your surrogate key transformation to add the two values together:

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Increment from existing maximum value

To seed the key value with the previous max, there are two techniques that you can use based on where your source data is.

Database sources

Use a SQL query option to select MAX() from your source. For example, Select MAX(<surrogateKeyName>) as maxval from <sourceTable>/

File sources

If your previous max value is in a file, use the max() function in the aggregate transformation to get the previous max value:

In both cases, you must join your incoming new data together with your source that contains the previous max value.

Data flow script

Syntax

Example

The data flow script for the above surrogate key configuration is in the code snippet below.

Next steps

These examples use the Join and Derived Column transformations.

Posted Jan 31, 2011

By Gregory A. Larsen

When designing a database to support applications you need to consider how you are going to handle primary keys. This article explores natural and surrogate keys, and discusses the pros and cons of each, allowing you to determine what makes the best sense in your environment when you are designing your databases.

To Generate A Surrogate Key Microsoft Access Uses A

When designing a database to support applications you needto consider how you are going to handle primary keys. There are two schoolsof thought, or maybe three. There are those that say primary keys shouldalways be a made up key, or what is commonly called a surrogate key. Otherssay there are good reasons to use real data as a key value; this type of key isknown as natural key. The third group is those that design their databases sotheir primary keys are a combination of natural and surrogate keys. In thisarticle, I’m going explore natural and surrogate key, and discuss the pros andcons of each. This will allow you to determine what makes best sense in yourenvironment when you are designing your databases.

Natural Key verses Surrogate Key

When you design tables with SQL Server, a table typically hasa column or a number of columns that are known as the primary key. The primarykey is a unique value that identifies each record. Sometimes the primary key ismade up of real data and these are normally referred to as natural keys, whileother times the key is generated when a new record is inserted into a table. When a primary key is generated at runtime, it is called a surrogate key. A surrogatekey is typically a numeric value. Within SQL Server, Microsoft allows you todefine a column with an identity property to help generate surrogate key values.

Before I talk about the pros and cons of natural andsurrogate keys, let me first expand a little more on each type of key. By doingthis you will have a better understanding of each of these two types of keys,and will have a more solid foundation to determine which type of key you shoulduse in your database design.

A natural key is a single column or set of columns thatuniquely identifies a single record in a table, where the key columns are madeup of real data. When I say “real data” I mean data that has meaning andoccurs naturally in the world of data. A natural key is a column value thathas a relationship with the rest of the column values in a given data record. Here are some examples of natural keys values: Social Security Number, ISBN, andTaxId.

A surrogate key like a natural key is a column that uniquelyidentifies a single record in a table. But this is where the similaritystops. Surrogate keys are similar to surrogate mothers. They are keys thatdon’t have a natural relationship with the rest of the columns in a table. Thesurrogate key is just a value that is generated and then stored with the restof the columns in a record. The key value is typically generated at run timeright before the record is inserted into a table. It is sometimes alsoreferred to as a dumb key, because there is no meaning associated with thevalue. Surrogate keys are commonly a numeric number.

Now that you have an understanding of the difference betweenthese two types of keys I will explore why you might use one key over theother. In the world of data architects, there is much debate over when it isappropriate to use a natural key and when a better solution would be to use asurrogate key. As already stated there are mainly just twodifferent camps. Some say you should always use a natural key and the otherssay a surrogate key is best. I suppose there is also a third camp that uses acombination of both natural keys and surrogate keys in their database design. Rather than state my opinion on which is best I’ll give you the pros and consof uses each and then you can decide with is best for your design.

Surrogate Key Pros and Cons

A definite design and programming aspect of working with databases is built on the concept that all keys will be supported by the use surrogate keys. To understand these programming aspects better, review these pros and cons of using surrogate keys.

Pros:

• The primary key has no business intelligence built into it.Meaning you cannot derive any meaning, or relationship between the surrogatekey and the rest of the data columns in a row.
• If your business rules change, which would require you to updateyour natural key this can be done easily without causing a cascade effectacross all foreign key relationships. By using a surrogate key instead of anatural key the surrogate key is used in all foreign key relationships. Surrogatekeys will not be updated over time.
• Surrogate keys are typically integers, which only require 4 bytesto store, so the primary key index structure will be smaller in size than theirnatural key counter parts. Having a small index structure means betterperformance for JOIN operations.

Cons:

• If foreign key tables use surrogate keys then you will berequired to have a join to retrieve the real foreign key value. Whereas if theforeign key table used a natural key then the natural key would be already beincluded in your table and no join would be required. Of course this I onlytrue if you only needed the natural key column returned in your query
• Surrogate keys are typically not useful when searching for datasince they have no meaning.

To Generate A Surrogate Key Microsoft Office

Natural Key Pros and Cons

Having natural keys as indexes on your tables mean you willhave different programming considerations when building your applications. Youwill find that pros and cons for natural keys to be just the opposite as thepros and cons for surrogate keys.

Pros:

• Will require less joins when you only need to return the keyvalue of a foreign key table. This is because the natural key will already beimbedded in your table.
• Easier to search because natural keys have meaning and will bestored in your table. Without the natural key in your table, a search for recordsbased on a natural key would require a join to the foreign key table to get thenatural key.

Cons:

• Requires much more work to change a natural key, especially whenforeign relationship have been built off the natural key.
• Your primary key index will be larger because natural keys aretypically larger in size then surrogate keys.
• Since natural keys are typically larger in size then surrogatekeys and are strings instead of integers joins between two tables on a naturalkey will take more time.

What Kind of Database Designer Are You?

To Generate A Surrogate Key Microsoft Email

There is much debate in the world of data modeling over whatkind of data should be used to support primary keys. There are some puristthat say all primary key should be surrogate keys, no matter how small thenatural key, or the fact that the natural key will never be updated. Other sayyou need to use natural keys because they make coding your application just somuch easier. When you design your databases, you need to decide what works bestin your environment. What kind of database designer are you and into which design camp do you fall?

» See All Articles by ColumnistGregory A. Larsen

To Generate A Surrogate Key Microsoft Account

Surrogate Key Definition