HP NonStop SQL/MP, Programming Manual

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Host Variables
HP NonStop SQL/MP Programming Manual for C—429847-008
2-9
Variable-Length Character Data
char prod_desc[6]; /* use for 5-character column */
EXEC SQL END DECLARE SECTION;
strcpy(prod_desc, "abc"); /* Copy 3 characters and */
/* null terminator */
...
/* Do not include space for null byte in the size */
blank_pad(prod_desc, sizeof prod_desc - 1);
EXEC SQL INSERT INTO =products VALUES (:prod_desc);
}
Variable-Length Character Data
The VARCHAR data type represents one data element; however, the C compiler
converts the type to a structure with two data items. The C compiler derives the group
item name from the VARCHAR column name and the names of the subordinate data
items, where:

len
is a numeric data item that represents the length.

val
is a fixed-length character data item for the string, plus an extra byte for the
null terminator, if the
SQL
pragma specifies the
CHAR_AS_STRING
option.
For example, if a column CUSTNAME is defined as VARCHAR(26), and the
SQL
pragma specifies the CHAR_AS_STRING option, INVOKE generates this structure:
struct
{
short len;
char val[27];
} custname;
You can refer to the individual data items or the structure name as host variables.
If you explicitly declare a structure as a host variable for a VARCHAR column (rather
than using INVOKE), declare the length as a
short
data type (and not an
int
).
Structures
You can refer to a structure name as a host variable only if the structure corresponds
to a VARCHAR data type. For structures that do not correspond to a VARCHAR data
type, the fields within the structure are the host variables. However, when you refer to
an individual field name in the structure, you must include the structure name with the
field name. For example, the structure
employee_info
contains the
empid
and
empname
fields:
EXEC SQL BEGIN DECLARE SECTION;
struct employee
{
long empid;
char empname[21];
} employee_info;
EXEC SQL END DECLARE SECTION;