SNOMED CT® Release Format 1 (RF1) Guide - ihtsdo

346 | SNOMED CT Release Format 1 (RF1) Guide July 2012
4.5.5.2.3. Generating a transitive closure table
There are various ways in which a transitive closure table can be generated. The method illustrated here
represents the smallest SQL query that might be used for this purpose. It is not the most efficient query and
may take several hours to run. However, it does offer a simple standard for comparing the results of alternative
approaches.
Table 260: Sample SQL for Deriving a Transitive Closure Table
-- Create simple sct_transitive closure table
-- This version uses varchar for string ConceptId values
-- An alternative would be to use bigint using the 64-bit integer representation
CREATE TABLE [sct_transitiveclosure] (
[SubtypeId] [varchar] (18) COLLATE Latin1_General_CI_AS NOT NULL ,
[SupertypeId] [varchar] (18) COLLATE Latin1_General_CI_AS NOT NULL ,
CONSTRAINT [PK_sct_transitiveclosure] PRIMARY KEY CLUSTERED
(
[SubtypeId]
[SupertypeId],
)
)
-- Add inverted index
CREATE INDEX [IX_sct_transitiveclosure] ON [dbo].[sct_transitiveclosure]([SupertypeId])
-- Initial row creation self reference
INSERT INTO [sct_transitiveclosure]([SupertypeId], [SubtypeId])
SELECT [ConceptId], [ConceptId] FROM [sct_concepts]
-- Further row creation
WHILE @@ROWCOUNT>0
-- Repeats while new rows are created by the following query
INSERT INTO [sct_transitiveclosure] ([SupertypeId], [SubtypeId])
SELECT distinct [ConceptId2],[tc].[SubtypeId] FROM [sct_relationships] INNER JOIN [sct_transitiveclosure]
as tc
ON [ConceptId1]=[tc].[SupertypeId]
LEFT OUTER JOIN [sct_transitiveclosure] As tc2
ON [ConceptId2]=[tc2].[SupertypeId] AND [tc].[SubtypeId]=[tc2].[SubtypeId]
WHERE [RelationshipType]='116680003' AND [tc2].[SubtypeId] is null
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