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manual abstract
Creating Services and Servers
Generating NonStop SQL Statements
A SELECT operation selects a single row from one table, protection view, or shorthand
view. A SELECT can only be generated on a unique access path.
As with all SQL operations, you can use the standard Pathmaker condition names for
SQL errors to check the status after the SELECT operation has completed.
Usage Considerations for
The generated code for a FETCH operation resides in paragraphs named
FETCH Operations
SQL-CURSOR-OPEN, SQL-CURSOR-FETCH, and SQL-CURSOR-CLOSE. If you
specified on the Operations Attributes screen “For Modification” equal to Y, two
additional paragraphs are generated: SQL-CURSOR-UPDATE and
SQL-CURSOR-DELETE. All code generated for FETCH operations uses an access
path.
In addition, the Pathmaker product creates an SQL cursor with the same name as the
SQL I/O section (with the hyphens replaced by underscores). The cursor definition
contains the appropriate WHERE clause to implement the “Position Mode” and the
“Start Position” you specified on the Operations Attributes screen for the FETCH
operation. The ORDER BY clause includes the access path columns and might contain
additional clauses to uniquely determine the sequence in which rows are accessed. If
you specified on the Operations Attributes screen “For Modification” equal to Y, the
cursor definition includes the FOR UPDATE clause; there is no ORDER BY clause.
To use these paragraphs, initialize the host variables, then PERFORM the
SQL-CURSOR-OPEN paragraph, PERFORM the SQL-CURSOR-FETCH paragraph
one or more times, then PERFORM the SQL-CURSOR-CLOSE paragraph.
Following each PERFORM, you can use the standard Pathmaker condition names for
SQL errors to check the status of the operation.
Selecting a Group of Rows
When the SQL-CURSOR-OPEN paragraph is performed, the rows to be fetched are
identified using a combination of the Sort Direction, the Position Mode, the Start
Position, and the host variable values. Rows are from a single table only.
The Sort Direction specifies whether rows are to be accessed in ascending or
descending order by access path column value.
The Position Mode identifies a subset of rows. If Position Mode is Table, all rows of
the table are selected. If Position Mode is Exact, all rows with access path column
values equal to the corresponding host variables are selected. If Position Mode is
Approximate and Sort Direction is ascending, all rows with access path column values
greater than or equal to the corresponding host variables are selected. If Position
Mode is Approximate and Sort Direction is descending, all rows with access path
column values less than or equal to the corresponding host variables are selected.
The Start Position establishes a starting position within the subset of rows defined by
the position mode. Specifically, Start Position identifies the row to be accessed the first
time the SQL-CURSOR-FETCH paragraph is performed. If Start Position is First, the
first row of the subset identified by the Position Mode will be accessed when the first
SQL-CURSOR-FETCH is performed. This row has the highest access path values if the
Sort Direction is descending or is the row with the lowest access path values if the Sort
4–66
067868 Tandem Computers Incorporated
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