Question

For a Perl library that dumps Sybase schemas for DBIx::Class (::Schema::Loader), I need to be able to introspect DEFAULTs and computed columns.

Suppose we have:

create table bar (
  id INTEGER IDENTITY PRIMARY KEY,
  foo VARCHAR(10) DEFAULT 'foo',
  adt AS getdate(),
  ts timestamp
)

Here’s as far as I got:

select substring(c.name,1,5) name, c.cdefault, c.computedcol from syscolumns c
join sysobjects o on c.id = o.id where o.name = 'bar' and o.type = 'U'

name       cdefault    computedcol 
---------- ----------- ----------- 
id                   0        NULL 
foo          602182610        NULL 
adt                  0   618182667 
ts                   0        NULL 

This tells me that column ‘foo’ has a stored procedure with id 602182610 that returns the value. How do I get the original DEFAULT ‘foo’ from this id?

The timestamp column does not have computed column object nor a default sproc, but I somehow need to know that it is in fact a timestamp column. Looking at the data type returned by DBI for it tells me that it’s ‘varbinary’, the internal representation of a timestamp. How do I know if it is or isn’t one?

It also tells me that column ‘adt’ is a computed column, the object for this column having id 618182667.

Looking in sysobjects for that id tells me little that seems useful except:

select substring(name,1,15) name, type from sysobjects where id = 618182667

name                           type 
------------------------------ ---- 
bar_adt_6181826                C    

Any help much appreciated.

Answer 1

Regarding your first question, about defaults

select text from syscomments 
where id = 602182610

As for timestamp columns, the type column in syscolumns references systypes.type. In that table name column contains the datatype name.