SQL Programming Manual for Pascal

NonStop SQL Version Issues
HP NonStop SQL Programming Manual for Pascal—528614-001
D-14
Using the Single-Code Thread Design
Advantages of this technique are:
°
Dynamic SQL is not necessary.
°
Program logic is simpler than in the single-code thread design.
•
Maintain a single-code thread by using IF/THEN/ELSE statements in the source
program; the statements test for the appropriate SQL version and choose between
two code branches at run time. This technique contrasts with the two-code thread
technique by performing version checking at run time instead of at compile time;
the use of the single-code thread technique precludes the use of the two-code
thread technique.
Typically, the single-code thread technique uses dynamic SQL and can require
extensive code to handle versions. The resulting single object file, however, needs
only a single build and release cycle to install the program on nodes of different
versions.
•
If you have a choice, use static SQL rather than dynamic SQL. Static SQL has
better performance than dynamic SQL because the SQL statements do not require
compilation at run time. Many generic release programs, however, require dynamic
SQL for other reasons.
•
Include the SQLGETSYSTEMVERSION procedure in program code to test for
system version. Then determine which code to execute depending on the version.
Using the Single-Code Thread Design
If your program is to run on both NonStop SQL C10 and C30 systems and uses
Version 2 features, the program probably uses dynamic SQL and not just static SQL.
The following guidelines apply to developing these generic release programs:
•
Pascal compile and bind the program on a C30 system and include the SQL
RELEASE1 directive in the source program. The RELEASE1 option is required
because the RELEASE1 format (C10) object code generated by the Pascal
compiler is upward compatible with the C30 SQL compiler, but RELEASE2 format
object code is not compatible with the C10 SQL compiler. The SQL RELEASE1
option instructs the Pascal compiler to generate RELEASE1 format SQLDAs and
produces output that is acceptable to a C10 SQL compiler as well as to a C30 SQL
compiler.
•
Do not use any Version 2 features in static SQL statements because these
statements will be processed by both the C10 and C30 SQL compilers as
described in the last item of the list.
•
Do not reference any Version 2 objects in static SQL statements, because these
objects will cause C10 SQL compilation errors.
•
Use Version 2 features and reference Version 2 objects only in dynamic SQL
statements because only the host variables that contain the SQL statements to be
executed are processed by the Pascal compiler. In dynamic SQL, SQL statements