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Permutations, Combinations, Sequences and Random Numbers/SQL Scripts/21 Merge Overlapping Records.sql

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+/*********************************************************************
+Scott Peters
+Merge Overlapping Records
+https://advancedsqlpuzzles.com
+Last Updated: 07/25/2022
+
+This script is written in SQL Server's T-SQL
+
+---------------------------------------------------------------------
+
+Script merges overlapping records
+I have broken the script into multiple steps to aid in understanding
+
+**********************************************************************/
+---------------------
+---------------------
+--Tables used in script
+DROP TABLE IF EXISTS #Numbers;
+DROP TABLE IF EXISTS #Distinct_StartIntegers;
+DROP TABLE IF EXISTS #OuterJoin;
+DROP TABLE IF EXISTS #DetermineValidEndIntegers;
+DROP TABLE IF EXISTS #DetermineValidEndIntegers2;
+GO
+
+---------------------
+---------------------
+--Create and populate #Numbers table
+CREATE TABLE #Numbers
+(
+StartInteger   INTEGER,
+EndInteger     INTEGER
+);
+GO
+
+INSERT INTO #Numbers VALUES
+(1,5),
+(1,3),
+(1,2),
+(3,9),
+(10,11),
+(12,16),
+(15,19);
+GO
+
+---------------------
+---------------------
+--Create and populate #Distinct_StartIntegers table
+--Step 1
+SELECT  DISTINCT
+        StartInteger
+INTO    #Distinct_StartIntegers
+FROM    #Numbers;
+GO
+
+---------------------
+---------------------
+--Create and populate #OuterJoin table
+--Step 2
+SELECT  a.StartInteger AS StartInteger_A,
+        a.EndInteger AS EndInteger_A,
+        b.StartInteger AS StartInteger_B,
+        b.EndInteger AS EndInteger_B
+INTO    #OuterJoin
+FROM    #Numbers AS a LEFT OUTER JOIN
+        #Numbers AS b ON a.EndInteger >= b.StartInteger AND
+                                a.EndInteger < b.EndInteger;
+GO
+
+---------------------
+---------------------
+--Create and populate #DetermineValidEndIntegers table
+--Step 3
+SELECT  EndInteger_A
+INTO    #DetermineValidEndIntegers
+FROM    #OuterJoin
+WHERE   StartInteger_B IS NULL
+GROUP BY EndInteger_A;
+GO
+
+---------------------
+---------------------
+--Create and populate #DetermineValidEndIntegers2 table
+--Step 4
+SELECT  a.StartInteger, MIN(b.EndInteger_A) AS MinEndInteger_A
+INTO    #DetermineValidEndIntegers2
+FROM    #Distinct_StartIntegers a INNER JOIN
+        #DetermineValidEndIntegers b ON a.StartInteger <= b.EndInteger_A
+GROUP BY a.StartInteger
+GO
+
+---------------------
+---------------------
+--Display the results
+--Step 5
+SELECT  MIN(StartInteger) AS StartInteger,
+        MAX(MinEndInteger_A) AS EndInteger
+FROM    #DetermineValidEndIntegers2
+GROUP BY MinEndInteger_A;
+GO