REGEX find 'SELECT FROM Z'

Hi

I'm running SAP program RS_ABAP_SOURCE_SCAN and enter string to search for as ^(?:SELECT)|(?:SELECT+\s)$ and select checkbox 'String is regular expression'.

This works okay, but it includes non-Z tables. I'd like to only get the SELECT statements from Z tables. But I'm not experienced enough and the examples I get are not clear. If you can adjust the REGEX above to extract SELECT statements only from Z tables, that would be great thanks.

Why is it required to have a similar expression split by a | character in REGEX? What is the purpose of the expression to the left and the one to the right?

Please assist.

Thanks,

Adrian