Thank you very much Mark for detailed info but i have more questions.

I am really curious.

Is this sql standard concept that i must do this in this crap way?

SELECT substring('ab11c' similar '[[:ALPHA:]]+#"[0-9]+#"[[:ALPHA:]]+' escape '#') FROM RDB$DATABASE

Also strange that i must consume whole string by reg expression not only part of it.

This can be as an option but as default it is strange for me.

Why not simply do:

SELECT substring('ab11c12bcd' similar '[0-9]+' itemNumber 1) FROM RDB$DATABASE

Will simply return „11”

SELECT substring('ab11c22bcd' similar '[0-9]+' itemNumber 2) FROM RDB$DATABASE

Will simply return 22

Now i have 2 udf like this:

REG_MATCH

REG_MATCH_COUNT

and i supposed that i can replace it with built in one, but i see that this is really terrible.

Above udfs i can use in this way

SELECT REG_MATCH(‘ab11c22bcd’, ‘[0-9]+’, 1) FROM RDB$DATABASE

Return 11

SELECT REG_MATCH(‘ab11c22bcd’, ‘[0-9]+’, 2) FROM RDB$DATABASE

Return 22

SELECT REG_MATCH_COUNT(‘ab11c22bcd’, ‘[0-9]+’) FROM RDB$DATABASE

Return 2

I can use it in the where clause:

SELECT * FROM MY_TABLE T WHERE REG_MATCH_COUNT(T.FIELD, ‘[0-9]+’)>2

Or

SELECT * FROM MY_TABLE T WHERE REG_MATCH(T.FIELD, ‘[0-9]+’, 1)=’11’

regards,

Karol Bieniaszewski