Can a Sybase SQL table have a computed column?

Sybase ASE does support computed columns, in two different formats ... virtual (value is determined each time column is selected) ... and materialized (value is (re)calculated when a base column's value is changed, with the (re)calculated value being written into the materialized/computed column).

An index can only be created on a materialized/computed column.

More details can be found in the Transact-SQL Users Guide

Not sure how far OP's gotten in the research so here are a few examples:

NOTE: assorted sp_help* output modified for brevity

Create virtual column with create table command:

create table mytab
(name    varchar(30)
,lname1  as lower(name)
)
go

sp_help mytab
go

 Column_name Type    Computed_Column_object          
 ----------- ------- --------------------------------
 name        varchar NULL                            
 lname1      varchar mytab_lname1_835531029 (virtual)

Verify index cannot be created on a virtual column:

create index idx1 on mytab(lname1)
go

Msg 1777, Level 16, State 1:
Server 'ASE400', Line 2:
Cannot create index on a virtual computed column (lname1). Modify it to materialized using the ALTER TABLE MODIFY commmand first and retry.

Modify column to be materialized:

alter table mytab
modify lname1 materialized
go

sp_help mytab
go

 Column_name Type    Computed_Column_object          
 ----------- ------- --------------------------------------
 name        varchar NULL                            
 lname1      varchar mytab_lname1_1139532112 (materialized) 

Now index can be created:

create index idx1 on mytab(lname1)
go
Non-clustered index (index id = 2) is being rebuilt.

sp_helpindex mytab
go

Object has the following indexes

 index_name index_keys index_description
 ---------- ---------- -----------------
 idx1        lname1    nonclustered 

Add another computed column via the alter table command, add an index:

alter table mytab
add lname2 as lower(name) materialized
go

create index idx2 on mytab(lname2)
go

sp_help mytab
go

 Column_name Type    Computed_Column_object          
 ----------- ------- --------------------------------------
 name        varchar NULL                            
 lname1      varchar mytab_lname1_1139532112 (materialized) 
 lname2      varchar mytab_lname2_1459533252 (materialized)

Object has the following indexes

 index_name index_keys index_description
 ---------- ---------- -----------------
 idx1        lname1    nonclustered 
 idx2        lname2    nonclustered 

Take for a test drive:

insert mytab (name) values ('Bob Smith')
go

select * from mytab
go

 name      lname1    lname2
 --------- --------- ---------
 Bob Smith bob smith bob smith

update mytab set name = 'Suzie Q'
go

select * from mytab
go

 name    lname1  lname2
 ------- ------- -------
 Suzie Q suzie q suzie q

FWIW, Sybase ASE also supports function-based indexes; under the covers a new materialized/computed column is created to support the index, eg:

create index idx3 on mytab(lower(name))
go

sp_help mytab
go

 Column_name Type    Computed_Column_object          
 ----------- ------- --------------------------------------
 name        varchar NULL                            
 lname1      varchar mytab_lname1_1139532112 (materialized) 
 lname2      varchar mytab_lname2_1459533252 (materialized)
 sybfi4_1    varchar mytab_sybfi4_1923534905 (functional index key)

Object has the following indexes

 index_name index_keys index_description
 ---------- ---------- -----------------
 idx1        lname1    nonclustered 
 idx2        lname2    nonclustered 
 idx3        sybfi4_1  nonclustered 

I apologise, I might have found the answer, which is to select directly into the computed value

v_Value COMPUTED(LOWER(v_Field1)

and forget any types.

The next problem is the index:

Cannot create index on a virtual computed column (v_Value). Modify it to materialized using the ALTER TABLE MODIFY commmand first and retry.