Surrogate keys are often used in data warehousing systems, as the high data volume in a data warehouse means that optimizing query speed becomes important. Using a surrogate key is advantageous because it is quicker to join on a numeric field rather than a non-numeric field. Apr 20, 2006 A sequence is just a surrogate key that restarts at 1 for each group of related records. For example, consider a table of log entries related to records in my t1 table: create table t1log( t1 int not null references t1(c1), seq int not null, message varchar(50) not null, primary key(t1, seq) ). Teradata has a concept of identity columns on their tables beginning around V2R6.x. These columns differ from Oracle's sequence concept in that the number assigned is not guaranteed to be sequential. The identity column in Teradata is simply used to. Show 5 replies. Re: How to generate surrogate keys with Teradata and Pushdown hiteshsahni Nov 26, 2014 1:00 AM (in response to tatup) Teradata's Identity column doesnot gurantee sequencing of the numbers. Gaps can be found even if identity column is used.

Teradata: Transpose Rows to Column

Sometime it is required to transpose rows into columns. This may be required for various business requirement and better analysis.Lets try to achieve this with the help of a table named 'Ledger' which contains company's sales for each quarter and company's sales for each quarter need to converted to columns.

Ledger Table: Creating a sample volatile table ledger with 3 columns to be transposed as shown below.
Data Population: Inserting few records in the table for transposing them to columns
Data View: Query To Generate Surrogate Key In Teradata

Query To Generate Surrogate Key In Teradata

Checking data in the 'ledger' table

Teradata Surrogate Key

Solution 1: Below query can transpose row to column for the given table 'ledger' using case statement.
Solution 2: Same result can be achieved using Teradata PIVOT function (introduced in TD 16).
Using PIVOT function with more groups of columns

Creating a table and populating sample data
Solution 1: It will be easier to use Teradata PIVOT (introduced in TD 16) function for more groups of columns.
Solution 2: Same result can be achieved using case statement

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.

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.

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 yo