Mysql INSERT SELECT problem (funny)

Question

I have a table with primary key id AUTOINCREMENT and some other attributes.

I have many rows with attribute lang='en'. and I do

DELETE FROM ".MY_PRF."form WHERE `lang` <> 'en'

I want to COPY all them changing lang to 'cz'

I use:

INSERT INTO form (`lang`, `caption`, `type`) 
SELECT 'cz', `caption`, `type` 
FROM form 
WHERE lang = 'en' 

This query produces an error

Duplicate entry '127' for key 1 

I don't know what's happening cause primary key is autoincrement

Please help me to solve my task. thanks.

Again, I want to copy rows with small change, the 'en' rows should remain

Answer 1

this realy is unlogical you insert an select from same table you have to select from another table

Answer 2

what is the type of ID variable?

If it is TINYINT change it to the INT

Answer 3

Why not just update?

UPDATE form SET lang = 'cz' WHERE lang = 'en'