AFAIK, this, and several other metadata changes are not allowed. Check
following issues (the most important IMHO missed in Derby) in Jira:
DERBY-342: At least basic (like operator) comparision between long
varchar (and clob). IMHO, related to DERBY-472 (see bellow).
DERBY-396, DERBY-119: Alter table DROP/RENAME/MODIFY column, suporting
rename of column even if part of referencial integrity; drop column with
release of space; modify column from NULL to NOT NULL - if NOT NULL
specified and table has records, then a DEFAULT is mandatory. Besides
it's not too usefull in production database, it's a fundamental feature
for development and upgrading times.
DERBY-239: Non-blocking online backup. A must have for production
databases 24 x 7 x 365.
DERBY-84: allow using column aliases in ORDER BY and HAVING because the
column alias could be a complex expression (in reality, I think its a
new variant from DERBY-84). Unique database I know allow this is MSSQL
since 2000 version (in ORDER BY - not in Having). Allow simplify queries.
DERBY-533, DERBY-554: Is a basic must-have for latin american
developers/users for adoption.
DERBY-472: Full-text indexing could allow very fast search. IMHO, it's
DERBY-342 related (if we could make full text searchs over long
varchar/clob would be amazing!).
Piotr Bzdyl escreveu:
Hello,
I found out that it is impossible to drop a column in a table in
derby. I thought that I can live with that if I could drop not null
constraint from the column I need to drop and leave that column unused.
But: how can I drop not null constraint on the column?
Best regards,
Piotr
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