Databases

SQL Server

  • SQL Server’s AlwaysOn Availability Groups is the built in mechanism for replication. With this feature turned on, a primary database is copied to other instances of SQL Server for read-only workload.
  • Read committed is the default isolation level in SQL Server
  • Temporal tables allow for tables to have the ability to keep history based on timestamps. The benefit of temporal tables is that you can specify a datetime and you can see what the value of the data in the table was at that point in time. Essentially, all data changes are tracked. Temporal tables are also called system-versioned temporal tables. 

T SQL

  • Check constraint for min value

ALTER TABLE [dbo].[Items] ADD CONSTRAINT CK_Items_Quantity_Minimum CHECK (Quantity >= 0)

Sharding

  • The main reason for wanting to partition/shard data is scalability 
  •  Can be used with transactional or analytics database systems 
  • Shards can be replicated

Document databases vs Graph databases

  • Document databases target use cases where relationships between one document and another are rare. Graph databases go in the opposite direction, targeting use cases where anything is potentially related to everything. 
  • One thing that document and graph databases have in common is that they typically don’t enforce a schema for the data they store, which can make it easier to adapt applications to changing requirements.

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