Currently, there is no support in SnowFlake for extended regular expression beyond the POSIX Basic Regular Expression syntax.
This warning is added every time a function call to REGEX_SUBSTR, REGEX_REPLACE, or REGEX_INSTR is transformed to SnowFlake to warn the user about possible unsupported regular expressions. Some of the features not supported are lookahead, lookbehind, and non-capturing groups.
SELECT REGEXP_SUBSTR('qaqequ','q(?=u)', 1, 1);
SELECT--** MSC-WARNING - MSCEWI2020 - REGEXP_SUBSTR FUNCTION ONLY SUPPORTS POSIX REGULAR EXPRESSIONS **REGEXP_SUBSTR('qaqequ','q(?=u)', 1, 1);
Check the regular expression used in each case to determine whether it needs manual intervention. More information about expanded regex support and alternatives in SnowFlake can be found here.