nPath Function Greedy Pattern Matching Example | Teradata Vantage - 17.05 - nPath Greedy Pattern Matching - Teradata Database

Teradata Vantage™ - Advanced SQL Engine Analytic Functions

prodname
Advanced SQL Engine
Teradata Database
vrm_release
17.00
17.05
created_date
June 2020
category
Programming Reference
featnum
B035-1206-170K

The nPath function uses greedy pattern matching, finding the longest available match despite any nongreedy operators in the pattern.

For example, consider the input table link2:

nPath Greedy Pattern Matching Examples Input Table link2
userid title startdate enddate
21 Chief Exec Officer 1994-10-01 2005-02-28
21 Software Engineer 1996-10-01 2001-06-30
21 Software Engineer 1998-10-01 2001-06-30
21 Chief Exec Officer 2005-03-01 2007-03-31
21 Chief Exec Officer 2007-06-01 null

The following query returns the following table:

SELECT job_transition_path, count(*) AS path_count FROM nPath (
  ON link2 PARTITION BY userid ORDER BY startdate
  USING
  Mode (NONOVERLAPPING)
  Pattern ('CEO.ENGR.OTHER*')
  Symbols (
    job_title like '%Software Eng%' AS ENGR,
    TRUE AS OTHER,
    job_title like 'Chief Exec Officer' AS CEO
  )
  Result (accumulate(job_title OF ANY(ENGR,OTHER,CEO)) AS job_transition_path)
) AS dt GROUP BY 1 ORDER BY 2 DESC;
job_transition_path path_count
[Chief Exec Officer, Software Engineer, Software Engineer, Chief Exec Officer, Chief Exec Officer] 1

In the pattern, CEO matches the first row, ENGR matches the second row, and OTHER* matches the remaining rows:


How pattern 'CEO.ENGR.OTHER*' matches cells in title column in greedy pattern matching example of Advanced SQL Engine function nPath

The following query returns the following table:

SELECT job_transition_path , count(*) AS path_count FROM nPath (
  ON link2 PARTITION BY userid ORDER BY startdate
  USING
  Mode (NONOVERLAPPING)
  Pattern ('CEO.ENGR.OTHER*.CEO')
  Symbols (
    job_title like '%Software Eng%' AS ENGR,
    TRUE AS OTHER,
    job_title like 'Chief Exec Officer' AS CEO
  )
  Result (accumulate(job_title OF ANY(ENGR,OTHER,CEO)) AS job_transition_path)
) AS dt GROUP BY 1 ORDER BY 2 DESC;
job_transition_path path_count
[Chief Exec Officer, Software Engineer, Software Engineer, Chief Exec Officer, Chief Exec Officer] 1

In the pattern, CEO matches the first row, ENGR matches the second row, OTHER* matches the next two rows, and CEO matches the last row:


How pattern 'CEO.ENGR.OTHER*.CEO' matches cells in title column in greedy pattern matching example of Advanced SQL Engine function nPath