Redesign of IColumn

Current state

Only differentiates between column creation and column alteration, but there are two ways to create a column and some databases (I'm looking at you, DB2) have a different syntax for both.
Difficult to change the order (some anonymous lambda array)

Use cases

Primary use cases

Column definition in CREATE TABLE
Column definition in ALTER TABLE ... ADD COLUMN
Column definition in ALTER TABLE ... ALTER COLUMN

Secondary use cases

PRIMARY KEY constraint
FOREIGN KEY constraint
Other constraints (optional)

How to fix it

Just some random ideas:

Using SQL fragments
SQL fragments wrapped in classes
- Pattern matching

Open questions

Maybe different API for all three use cases?
How to handle the seconday use cases?