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

redshift should support similar to.

WHERE field1 SIMILAR TO '[0-9]{4}%'

This reads as where field1 starts with 4 characters in the range of 0-9, then anything else.