SQL Azure Federations allow horizontal scaling of databases in SQL Azure. Federations partition database tables across multiple database servers or shards. Each federation member contains a subset of rows from a table based on the federation key value. The root member contains metadata and global data while federation members provide physical data separation and can have their own schemas. However, federations have limitations such as requiring an INT, BIGINT, UNIQUEIDENTIFIER or VARBINARY distribution key and not supporting NULL values or IDENTITY properties for federated columns.

1. SQL Azure Federations
Pavlo Revenkov
EPAM Cloud Computing Competency Center
Email: pavlo_revenkov@epam.com
Skype: rp_risingstar

2. Scaling
Horizontal partitioning is a database design principle whereby rows of a
database table are held separately. Each partition forms part of a shard, which
may in turn be located on a separate database server or physical location.
© Wikipedia
Vertical Horizontal
DB
server
DB
server
DB
server
time
Member
#1
Member
#2
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time
Root
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3. Does not contain the data anymore.
It is distributed across shards.Root
Horizontal scaling 3

4. Infrastructure 4
Federation
root
Federation
member
…
- contains federation metadata;
- global database data;
- route connections.
- provides physical data separation;
- can have its own schema;
Atomic unit
Federation
member
- the collection of all rows in a
federation member that match
a specific federation key value.

5. Limitations 5
• The federation distribution key must be an
INT, BIGINT, UNIQUEIDENTIFIER, or VARBINARY and specifies a
range value.
• Federation columns cannot be NULL-able.
• Federated members do not support the IDENTITY property.
• Reference tables cannot have foreign key relationships with federated
tables. Federated tables can have foreign key relationships with
reference tables without restrictions.
• Each federation member cannot be larger than 150 GB.
• Cross database joins are not supported. An application must implement
the logic for joining data from multiple federation members or multiple
federations.

6. Demo 6

7. References
Federations in Windows Azure SQL Database:
 http://msdn.microsoft.com/en-us/library/windowsazure/hh597452.aspx
SQL Database Federations Tutorial:
 http://msdn.microsoft.com/en-us/library/windowsazure/hh778416.aspx
Federation Guidelines and Limitations:
 http://msdn.microsoft.com/en-us/library/windowsazure/hh597469.aspx
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8. Questions? 8