SQL/MP Programming Manual for COBOL

Host Variables

HP NonStop SQL/MP Programming Manual for COBOL—529758-003

2-22

Using Indicator Variables With the INVOKE Directive

The INVOKE directive automatically generates a two-byte indicator variable (data type

short) for each host variable that corresponds to a column that allows a null value. The

name of the indicator variable is the same name as the corresponding column plus a

prefix, if you specify one, and a suffix. If you do not specify a prefix or suffix, INVOKE

appends the default suffix -I to the name.

If a column name is 30 characters and the default indicator suffix -I is used, the -I is

truncated, and the indicator variable name is then identical to the corresponding host

variable name. To prevent this problem, use the PREFIX or NULL STRUCTURE

clause for column names that are 30 or 31 characters.

The format of the indicator variable name depends on the PREFIX, SUFFIX, and NULL

STRUCTURE clauses.

PREFIX and SUFFIX Clauses

The PREFIX and SUFFIX clauses causes INVOKE to generate an indicator variable

name derived from the column name and the prefix or suffix. A default suffix of -I

applies if the INVOKE directive omits these clauses. For example, if the column name

is RETIRE-DATE, the format of the indicator variable is RETIRE-DATE-I.

You can specify a suffix other than an I by specifying a SUFFIX clause with the

INVOKE statement. Or, you can replace the suffix with a prefix of your choosing by

specifying the PREFIX clause.

This INVOKE directive specifies both a prefix and a suffix for the indicator variables:

EXEC SQL INVOKE BTABLE PREFIX I- SUFFIX -END END-EXEC.

The HP COBOL compiler generates this structure:

* Record Definition for table \SYS1.$VOL1.SUBV1.BTABLE

* Definition current at 12:41:14 - 06/11/94

01 BTABLE.

02 I-ZCHAR-NULL-OK-END PIC S9(4) COMP.

02 ZCHAR-NULL-OK PIC X(10).

02 I-ZNUM-NULL-OK-END PIC S9(4) COMP.

02 ZNUM-NULL-OK PIC S9(4) COMP.

NULL STRUCTURE Clause

The NULL STRUCTURE clause causes INVOKE to generate a group item for columns

that contain the indicator variables. The group item name is derived from the column

name. For example, a column named RETIRE-DATE has this format:

02 RETIRE-DATE.

03 INDICATOR PIC S9(4) COMP.

03 VALUE PIC X(10).