SQL/MX 3.2 Programming Manual for C and COBOL (H06.25+, J06.14+)

Host Variables in C/C++ Programs

HP NonStop SQL/MX Release 3.2 Programming Manual for C and COBOL—663854-002

3-18

Variable-Length Character Data



INSERT

test1.len = 3;

Strcpy(test1.val,"abc");

EXEC SQL INSERT INTO t1 VALUES(:test1);



UPDATE

EXEC SQL UPDATE t1 SET name = :test1 WHERE name = 'xyz';

Generating Structures Instead of Using Null-Terminated

Strings

Prior to SQL/MX Release 1.8, all C/C++ VARCHAR columns were interpreted as null-

terminated strings. Beginning with SQL/MX Release 1.8, NonStop SQL/MX

implemented the -a preprocessor option, which translates VARCHAR host variables

into structures that contain the correct length and string fields. This behavior is similar

to invoked VARCHAR, which is generated as a structure with a length followed by a

string. If a VARCHAR structure is also a rowset, an additional array specification is part

of the structure definition.

In C/C++, the default behavior of the VARCHAR host variable type is:

VARCHAR hvar[size+1];

This host variable is translated to:

char hvar[size+1];

When you specify the -a option, the preprocessor generates this structure:

struct{

short len;

char val[size+1];

} hvar;

Inserting or Updating Variable-Length Character Data

The rules for selecting and inserting or updating variable-length character data are

similar to the rules for fixed-length character data with one exception. When inserting

or updating data with VARCHAR data type, you do not have to pad the array with

blanks.

Example: Using a Null-Terminated String

Using the SQL/MX default for VARCHAR (for example, null terminated string), this

example uses a VARCHAR declaration for an SQL column up to 11 characters in length:

EXEC SQL BEGIN DECLARE SECTION;

unsigned NUMERIC (4) hv_prod_num;

VARCHAR hv_prod_desc[11];

EXEC SQL END DECLARE SECTION;

...