REGEXP_SUBSTR Function in Aster - forum topic by sajmal

Hi, 
I am using following REGEXP_SUBSTR in Teradata 14 and result is fine. 
 

SELECT REGEXP_SUBSTR(SUBSTR('This is sample text day_of_month is 17--this value should be returned',POSITION( 'day_of_month' IN 'This is sample text day_of_month is 17--this value should be returned'),50),  '[[:digit:]]+', 1 ) AS Day_Of_Month

Result: 17
But when I am trying to execute the same in Aster. It gives the error that regexp_substr is not supported. Can anybody help me to know what is the equivalent way to achieve the purpose in Aster. 
 
Regards,
Saj