I want to point out that the problem is more subtle than you may think
Indeed. The difference between two versions of a table can be missing columns, which is fairly easy to manage, or more subtle things like NULL/NOT NULL, primary key, constraints, and a host of other things.
Consider Sybase's CREATE TABLE syntax:
create table [database .[owner ].]table_name (column_name datatype
[default {constant_expression | user | null}]
{[{identity | null | not null}]
[off row | [ in row [ (size_in_bytes) ] ]
[[constraint constraint_name ]
{{unique | primary key}
[clustered | nonclustered] [asc | desc]
[with { fillfactor = pct, max_rows_per_page = num_rows, }
reservepagegap = num_pages }]
[on segment_name]
| references [[database .]owner .]ref_table
[(ref_column )]
[match full]
| check (search_condition)}]}
[match full]...
| [constraint constraint_name]
{{unique | primary key}
[clustered | nonclustered]
(column_name [asc | desc]
[{, column_name [asc | desc]}...])
[with { fillfactor = pct, max_rows_per_page = num_rows ,
reservepagegap = num_pages } ]
[on segment_name]
|foreign key (column_name [{,column_name}...])
references [[database.]owner.]ref_table
[(ref_column [{, ref_column}...])]
[match full]
| check (search_condition) ... }
[{, {next_column | next_constraint}}...])
[lock {datarows | datapages | allpages }]
[with { max_rows_per_page = num_rows,
exp_row_size = num_bytes,
reservepagegap = num_pages,
identity_gap = value } ]
[on segment_name ]
[ [ external table ] at pathname ]
Obviously, creating an UPDATE TABLE request that will automatically make the two versions of a table identical becomes non-trivial if all of these syntax elements need to be handled.
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