DB2: find field value where first character is a lower case letter

Question

I am trying to pick out a value in a field where the first character is a lower case letter. This is difficult since DB2 does not permit regular expressions. My current attempt is:

select * from mytable
where field1 like lcase('_%')

where I was hoping the underscore followed by percent wildcard would find any character in the first position, and then wrap the lcase() around that to ensure it is lower case. the result is that any and every value gets selected, so the lcase() is not performing what I want it to do, and in hindsight is used to cast to lowercase.

With that in mind, how to I ensure that the result of

('_%')

is lowercase only?

Thanks very much

Answer 1

i would use something like:

... where substr(field1,1,1) <> upper(substr(field1,1,1))

solution with 'a'...'z' will not work with characters different from latin characterset (e.g. cyrilic etc)

Answer 2

Why not

where field1 >= 'a' and field1 < '{'

This will even make use of an appropriate index, if any. Be warned, however, that this won't work when your DB instance does lexicongraphic ordering. I am not sure if the latter is a DB attribute or a session attribute, however.

Another, more general way (especially when considering non ASCII letters) would be to check if the length of the field is > 0 and the lowercased substring consisting of the first character equals the substring consisting of the first character while the uppercased first character does not equal the first character. (Look up the functions in the DB2 reference, I have mine not ready at the moment.)

Answer 3

DB2 DOES allow Regular expressions with xQuery. For example:

with cteGender(VALUE) as
(
values
('M'),('F'),('U'),('S'),(' M'),('f')
),
cteResult(VALUE,RESULT_BOOLEAN) as
(
select '"' || VALUE || ‘"',
xmlquery('fn:matches($VALUE,''^[MFU]{1}$'')') from cteGender
)
select VALUE, RESULT_BOOLEAN,
xmlcast(RESULT_BOOLEAN as integer) RESULT_INTEGER from cteResult;

I took this example from: http://www.idug.org/p/bl/et/blogid=278&blogaid=187 That article explain very well how to use xQuery.

DB2 does not have SQL functions for Regular Expressions, but with xQuery you can do that. But if you really want SQL functions for RegEx, please visit this site: https://www.ibm.com/developerworks/jp/data/library/db2/j_d-regularexpression/ (In Japanese, but the code can be understood)

For more information about RegEx in DB2 please visit: http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.xml.doc/doc/xqrregexp.html