Usage for tsequal

There are additional considerations for using tsequal.

tsequal, a system function, compares the timestamp column values to prevent an update on a row that has been modified since it was selected for browsing. For general information about system functions, see Transact-SQL Users Guide.
tsequal allows you to use browse mode without calling the dbqual function in DB-Library. Browse mode supports the ability to perform updates while viewing data. It is used in front-end applications using Open Client and a host programming language. A table can be browsed if its rows have been timestamped.
To browse a table in a front-end application, append the for browse keywords to the end of the select statement sent to the SAP ASE server. For example:
```
Start of select statement in an Open Client application 
...  
   for browse

Completion of the Open Client application routine
```
Do not use tsequal in the where clause of a select statement; only in the where clause of insert and update statements where the rest of the where clause matches a single unique row.

If you use a timestamp column as a search clause, compare it like a regular varbinary column; that is,timestamp1 = timestamp2.

Adding a Timestamp to an Existing Table

To prepare an existing table for browsing, add a column named timestamp using alter table. For example, to add a timestamp column with a NULL value to each existing row:

alter table oldtable add timestamp

To generate a timestamp, update each existing row without specifying new column values:

update oldtable
set col1 = col1