Data Retrieval on Sybase
The SYB connector supports the read and selectdb ProcScript statements, with some restrictions.
Stepped Hitlist
The stepped hitlist mechanism is fully supported.
By default, the SYB connector uses a step size of ten (although Uniface sometimes optimizes queries
and uses a more optimal step size). This can be overruled by the
step size connector option. For more information, see step size.
If an application normally handles more than ten but fewer than 100 records on one form, setting the step size to 100 is useful.
When printing large amounts of data in batch mode
with the clear (C) printing option, it is not advisable to disable the stepped
hitlist. Without the stepped hitlist, Uniface would have to select everything before starting to
format the print file; the time gained with the C option would be lost.
Note: When printing large amounts of data in batch
mode with the clear (C) printing option, it is not advisable to disable the
stepped hitlist. Without the stepped hitlist, Uniface would have to select everything before
starting to format the print file; the time gained with the C option would be
lost.
Note: The Uniface stepped hitlist is managed using
Sybase cursors. If this results in performance problems, you may need to set the
same select and rowcount connector options, in
combination with the step size. For more information, see Same-Select Mechanism for Hitlist Management.
read
The read ProcScript statement
is fully supported, including the
where and order by clauses.
When using the
where clause, all text between the double quotation marks
("") is inserted into the generated select statement literally
as entered. If the Sybase DBMS is configured for ANSI comparisons (ansinull on,
which is the default), the results returned by where do not contain null values.
You need to write search conditions accordingly. For more information, consult the Sybase
documentation.
Sybase handles the u_where
clause in all circumstances, and this profile works correctly whether or not the logon path is
configured for ansinull.
The order by qualifier is
supported. Text and Image fields cannot be included in this qualifier. Sybase does not support the
creation of views which include the
order by qualifier, but when a view is created, this qualifier can be used
to access the view.
selectdb
Sybase and the SYB connector handle the selectdb instruction in all circumstances. For performance reasons, when you use the selectdb ProcScript command, the SYB connector returns the first selected row .
To avoid losing precision, the SYB connector returns a Floating point value (F8) when an average is performed on Integers (Sybase Tinyint, Smallint, and Integer fields). This is done
When a sum is performed on a Sybase Tinyint or Smallint field (I1 or I2), an Integer is returned (I4). Also, when a sum is performed on a Sybase Real field (F4), a Float (F8) is returned. This is done to avoid losing precision.
The following table contains a list of Sybase fields that have restrictions imposed when using selectdb functions:
| Sybase field | max | min | sum | ave | count |
|---|---|---|---|---|---|
| Bit | No | No | No | No | Yes |
| Text | No | No | No | No | No |
| Image | No | No | No | No | No |
| Binary | Yes | Yes | No | No | Yes |
| Varbinary | Yes | Yes | No | No | Yes |
| Char | Yes | Yes | No | No | Yes |
| Varchar | Yes | Yes | No | No | Yes |
| Datetime | Yes | Yes | No | No | Yes |
| Smalldatetime | Yes | Yes | No | No | Yes |
Retrieve sequential
The retrieveSequential trigger is not supported.
