Overview
The Pervasive PSQL relational interface includes support for COBOL OCCURS constructs, partial REDEFINES, and variable record layouts.
A partial REDEFINE redefines a portion of the data within a record (such as a 05 level within a 01 level). A variable record layout is also referred to as a REDEFINES because the entire record is being redefined. To avoid confusion with terminology, this section refers to partial REDEFINES and to variable record layouts.
No changes are required to your COBOL application to take advantage of the SQL access.
You enable SQL access by describing the application’s understanding of data to the Pervasive PSQL relational interface. In developer’s terms, you define the metadata to the relational interface.
Note that this section applies only to COBOL applications that include OCCURS, partial REDEFINES, or variable record layouts.
Restrictions
The following restrictions currently apply to providing SQL access for COBOL applications.
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OCCURS cannot be nested within OCCURS
•
OCCURS cannot be nested within partial REDEFINES
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Partial REDEFINES cannot be nested within partial REDEFINES
•
Partial REDEFINES cannot be nested within OCCURS
•
Only one index can be defined for an OCCURS. Additional indexes cannot be defined for the items within the OCCURS.
•
The only data types supported are those defined for the Pervasive PSQL transactional and relational interfaces. The data types are described in the XML control file by using only the transactional data types. See cobolschemaexec.xsdin Table 196 for a discussion of the XML control file. For a discussion of data types, see Pervasive PSQL Supported Data Types in SQL Engine Reference.
SQL Statements
The following table lists the use of SQL statements with data tables created from OCCURS, partial REDEFINES, or variable record layouts.
Table 195
Use of SQL Statements With COBOL Data Constructs  
Statement
Use with OCCURs and partial REDEFINES
Use with Variable Record Layouts
Notes
ALTER TABLE
No
No
 
CREATE INDEX
No
No
 
CREATE INDEX IN DICTIONARY
No
Yes
 
CREATE TRIGGER
No
No
 
DELETE
No
Yes
 
DROP TABLE
Yes
Yes
A DROP TABLE statement removes all of the entries from the system tables. The data file itself is not deleted or modified. Also, when you drop a main table, a message informs you to drop any dependent tables if any are detected. A dependent table depends on a main table and results from conditions such as an OCCURS that contains an index or from partial REDEFINES. Once you drop the dependent tables, you can drop the main table.
INSERT INTO
No
No
 
UPDATE
Yes
Yes
An UPDATE statement cannot update a column on which a table filter has been defined. A table filter is a logical expression associated with a table. Table filters are defined as part of your metadata in the XML files.
all other SQL statements listed in SQL Engine Reference.
Yes
Yes
See Grammar Statements in SQL Engine Reference.