OpenEdge Data Management: DataServer for Microsoft SQL Server

Initial Programming Considerations
2–58
The size of r-code grows significantly when you compile procedures against a MS SQL Server
data source as compared to compiling against an OpenEdge database. The r-code for a
DataServer application contains as text portions of SQL statements that the DataServer passes
to the data source.
FOR statements
FOR FIRST and FOR LAST statements that cause the DataServer to sort data before returning it to
the client behave differently when returning data from a MS SQL Server data source than when
returning data from an OpenEdge database. The data source might not sort data like the
OpenEdge database does, so the order in which records return might differ. In addition, the
server-side result set is limited to a single record to improve performance.
Features and language differences
The DataServer supplies you with complete ABL functionality when accessing MS SQL Server
data sources. Many ABL language elements (statements, functions, and so forth) and Data
Dictionary features work the same whether your application accesses a data source through the
DataServer or an OpenEdge database.
Use the DBRESTRICTIONS function to find out which OpenEdge features your MS SQL Server
data source does not support. For the DataServer for MS SQL Server, DBRESTRICTIONS can
return SETUSERID and COUNT–OF. In certain circumstances, it can return additional values. For
example, it can return READ–ONLY if you connect to the schema holder in read-only mode. See
the “DBRESTRICTIONS function” reference entry in OpenEdge Development: ABL Reference
for information on syntax.
Table 2–15 summarizes ABL differences between OpenEdge databases and MS SQL Server
data sources.
Table 2–15: ABL differences between OpenEdge Databases and MS SQL
Server data sources (1 of 2)
OpenEdge feature MS SQL Server data source difference
CONTAINS operator This operator relates to word indexing, which the
DataServer does not support.
COUNT–OF function The DataServer does not support this function.
CREATE statement Records that you create after opening a cursor
might be invisible to that cursor.
FIND statements
FOR EACH statements
OPEN QUERY statement
MATCHES function
BEGINS function
To reduce the number of records included in the
results set, qualify your FIND statements and
queries with a WHERE clause.
The DataServer does not support using the percent
(%) or underscore (_) character with the MATCHES
and BEGINS functions. Do not use these functions
with a pattern that is not an expression.
Note: It is theoretically possible to do this with an
OpenEdge database, but using this kind of criteria
results in poor performance.