Insert Statement Issues

I'm to add a record and am having problems

Assuming my table (cat) has

keyfield (number - primary), item_id (text - required)

insert into cat (keyfield, item_id) values (keyfieldvalue,'2001.25b')

the problem comes with the keyfielvalue, I need to increment the primary key by one. I tried the following

insert into cat (keyfield, item_id) values (max(keyfield)+1,'2001.25b') insert into cat (keyfield, item_id) values ((select max(keyfield)+1 from cat),'2001.25b')

ORA-00936: missing expression

If I trade the max query for a straight out number it works fine

insert into cat (keyfield, item_id) values (1457,'2001.25b')

So how do I get the largest value in the table at present and then use it in my statement ?

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James Starritt