= Customisations made to i2b2

== 1. Remove primary key from Observation Fact table in Data database

=== Rationale

The primary key creates a unique constraint on Encounter_Num, Concept_Cd, Provider_Id, Start_Date & Modifier_Code.  However, we have genuine data that is duplicated on these fields.  For example, a repeat test on the same sample where the first was inconclusive.

=== Applied To

The customisation has been applied to the following i2b2 instances:

* i2b2_b1_data

=== Customisation

To apply the customisation, run the following SQL in the i2b2 data database:

{{{
#!sql
ALTER TABLE [dbo].[Observation_Fact] DROP CONSTRAINT [OBSERVATION_FACT_PK]
GO
}}}

=== Roll Back

To roll back the customisation, run the following SQL in the i2b2 data database:

{{{
#!sql
ALTER TABLE [dbo].[Observation_Fact] ADD  CONSTRAINT [OBSERVATION_FACT_PK] PRIMARY KEY NONCLUSTERED 
(
	[Encounter_Num] ASC,
	[Concept_Cd] ASC,
	[Provider_Id] ASC,
	[Start_Date] ASC,
	[Modifier_Cd] ASC
)
GO
}}}