SQL/MX Programming Manual for C and COBOL (G06.24+, H06.03+)

Dynamic SQL With Descriptor Areas
HP NonStop SQL/MX Programming Manual for C and COBOL—523627-004
10-12
Steps for Using SQL Item Descriptor Areas
Steps for Using SQL Item Descriptor Areas
Figure 10-1 shows the steps presented within the complete C program. These steps
are executed in the sample program Example A-4 on page A-8.
Figure 10-1. Using SQL Descriptor Areas in a C Program
EXEC SQL BEGIN DECLARE SECTION;
char hv_sql_statement[256];
long in_value;
short num;
/* Declare host variables for item descriptor values. */
long num_data;
char char_data[100];
...
EXEC SQL END DECLARE SECTION;
... /* Construct the SQL statement from user input. */
desc_max = 1;
EXEC SQL ALLOCATE DESCRIPTOR 'in_sqlda' WITH MAX :desc_max;
desc_max = 6;
EXEC SQL ALLOCATE DESCRIPTOR 'out_sqlda' WITH MAX :desc_max;
EXEC SQL PREPARE sqlstmt FROM :hv_sql_statement;
...
EXEC SQL DESCRIBE INPUT sqlstmt USING SQL DESCRIPTOR 'in_sqlda';
EXEC SQL DESCRIBE OUTPUT sqlstmt USING SQL DESCRIPTOR 'out_sqlda';
desc_value = 1;
EXEC SQL SET DESCRIPTOR 'in_sqlda' VALUE :desc_value
VARIABLE_DATA = :in_value;
EXEC SQL EXECUTE sqlstmt USING SQL DESCRIPTOR 'in_sqlda'
INTO SQL DESCRIPTOR 'out_sqlda';
EXEC SQL GET DESCRIPTOR 'out_sqlda' :num = COUNT;
for (i = 1; i<= num; i++) {
EXEC SQL GET DESCRIPTOR 'out_sqlda' VALUE :i
:type = TYPE,
:length = LENGTH,
:name = NAME;
/* Test type or name to determine the compatible host variable. */
if ...
EXEC SQL GET DESCRIPTOR 'out_sqlda' VALUE :i
:num_data = VARIABLE_DATA;
...
}
... /* Process the values from the item descriptor areas. */
EXEC SQL DEALLOCATE PREPARE sqlstmt;
EXEC SQL DEALLOCATE DESCRIPTOR 'in_sqlda';
EXEC SQL DEALLOCATE DESCRIPTOR 'out_sqlda';
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