SQL/MP to SQL/MX Database and Application Migration Guide

Converting SQL/MP Applications to SQL/MX
Applications
HP NonStop SQL/MP to NonStop SQL/MX Database and Application Migration Guide—666211-001
4-47
Dynamic SQL
FOR clause, and if ORDER BY or GROUP BY is specified for the cursor or if the query
expression defining the cursor specifies a read-only table, the cursor defaults to
read-only. It is the query that determines that the table is read-only, not the table’s
attributes. Otherwise, the cursor defaults to updatable (without a column list). If you
know that you are not going to update a cursor, specify FOR READ ONLY.
FETCH Statement
In NonStop SQL/MP, when a FETCH statement executes, if the number of host
variables is different from the number of columns in the result table of the declared
cursor, a warning is issued, and NonStop SQL/MP returns the number of values in the
shorter list.
In NonStop SQL/MX, the number of host variables must be the same as the number of
columns in the result table or an error is returned.
Positioned UPDATE Statement
In NonStop SQL/MP, you can execute the UPDATE...WHERE CURRENT OF
statement for static SQL only.
In NonStop SQL/MX, you can execute the UPDATE...WHERE CURRENT OF
statement for static SQL and dynamic SQL.
Dynamic SQL
Dynamic SQL allows a program to construct, compile, and execute a SQL statement at
run time. NonStop SQL/MP provides a descriptor area, referred to as the SQLDA,
containing information about input parameters and output variables in dynamic SQL
statements.
NonStop SQL/MX provides for the allocation of a descriptor area with the use of
SQL:1999 dynamic SQL statements. Unlike NonStop SQL/MP, the SQL/MX application
cannot access the descriptor directly. Access to the descriptor is encapsulated using
ANSI SQL:1999 statements. This descriptor area consists of multiple item descriptor
areas, together with a count of the number of those item descriptor areas. For further
information about using the descriptor area, see Descriptor Area
on page 4-48.
The next list summarizes the dynamic SQL statements that you use with a SQL/MX
descriptor area. For information about the syntax and use of these statements, see the
SQL/MX Reference Manual.
ALLOCATE DESCRIPTOR Allocates an input or output SQL descriptor area.
DEALLOCATE DESCRIPTOR Deallocates a SQL descriptor area.
GET DESCRIPTOR Retrieves information from a SQL descriptor area—
the COUNT of the item descriptor areas and
specified fields in the areas.
SET DESCRIPTOR Modifies information in a SQL descriptor area.