classifier function
Applies to: 
Databricks SQL Databricks Runtime 19.0 and above
Beta
This feature is in Beta.
Returns the name of the pattern variable that the current row matched. Use classifier() in ALL ROWS PER MATCH output to label each row with its role in the pattern. Use this function only in the MEASURES and DEFINE clauses of MATCH_RECOGNIZE.
Syntax
classifier()
Arguments
This function takes no arguments.
Returns
A STRING.