SQL Server's isNumeric() equivalent in amazon redshift

Question

• I\'m using amazon redshift as my data warehouse
• I have a field (field1)of type string. Some of the strings start with four numbers and others with letters:

Answer 1

Per Amazon, the posix style ~regex style expressions are slow... https://docs.aws.amazon.com/redshift/latest/dg/pattern-matching-conditions.html

Using their own REGEXP_* functions seems to be faster. https://docs.aws.amazon.com/redshift/latest/dg/String_functions_header.html

For checking just a true/false for integers I've been using the following with success. REGEXP_COUNT(my_field_to_check, '^[0-9]+$') > 0

this returns 1 if only numeric, 0 if anything else