HP 3000 Manuals HP 3000 Manuals
Understanding Dynamic Parameters
A dynamic parameter has the following characteristics:
* It is an input value to the database.
* It is specified as a question mark within a string in a prepared
statement in your application.
* Its datatype is determined based on its use in the prepared
statement.
* You assign its value at run time via a host variable or a data
buffer array.
* It is replaced by its assigned value when the OPEN or EXECUTE
statement executes.
For example, the following statement specifying two dynamic parameters
could be put into a string in your program:
UPDATE PurchDB.Parts SET SalesPrice = ? WHERE PartNumber = ?
The string itself can be used as a parameter of the PREPARE statement, or
it can be assigned to a host variable that is a parameter of the PREPARE
statement, as shown in the following sections.
Examples in C of Preparing a Statement with Dynamic Parameters
The following example uses a string as a parameter of the PREPARE
statement:
EXEC SQL PREPARE CMD1 FROM 'INSERT INTO PurchDB.Parts (PartNumber,PartName)
VALUES (?,?);';
In the following example, a host variable is used:
In the declare section, declare a character array host variable (large enough
to hold the string plus one byte) for a delimiting ASCII 0:
EXEC SQL BEGIN DECLARE SECTION;
:
char DynamicCmdLine[81];
:
EXEC SQL END DECLARE SECTION;
:
Assign the string to the host variable:
strcpy(DynamicCmdLine,"INSERT INTO PurchDB.Parts (PartNumber, PartName)");
strcpy(tmpstr, " VALUES (?,?);");
strcat(DynamicCmdLine,tmpstr);
Prepare the statement:
EXEC SQL PREPARE CMD1 FROM :DynamicCmdLine;
Examples in COBOL of Preparing a Statement with Dynamic Parameters
The following example uses a string as a parameter of the PREPARE
statement:
EXEC SQL PREPARE CMD1 FROM "INSERT INTO PurchDB.Parts (PartNumbe
- r, PartName") VALUES (?,?);"
END-EXEC.
In the following example, a host variable is used:
In the declare section, declare a host variable large enough to hold the string:
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
:
01 DYNAMICCMD PIC X(80).
:
EXEC SQL END DECLARE SECTION END-EXEC.
:
Assign the string to the host variable:
MOVE "INSERT INTO PurchDB.Parts (PartNumber, PartName)" TO TEMP1.
MOVE " VALUES (?,?);" TO TEMP2.
STRING TEMP1 DELIMITED BY SIZE
TEMP2 DELIMITED BY SIZE
INTO DYNAMICCMD.
Prepare the statement:
EXEC SQL PREPARE CMD1 FROM :DYNAMICCMD END-EXEC.
Examples in FORTRAN of Preparing a Statement with Dynamic Parameters
The following example uses a string as a parameter of the PREPARE
statement:
EXEC SQL PREPARE CMD1 FROM 'INSERT INTO PurchDB.Parts
1 (PartNumber,PartName) VALUES (?,?);'
In the following example, a host variable is used:
In the declare section, declare a host variable large enough to hold the string:
EXEC SQL BEGIN DECLARE SECTION
CHARACTER*80 DynamicCommand
EXEC SQL END DECLARE SECTION
:
Assign the string to the host variable:
DynamicCommand = 'INSERT INTO PurchDB.Parts (PartNumber,PartName)
1 VALUES (?,?)'
Prepare the statement:
EXEC SQL PREPARE CMD1 FROM :DynamicCommand
Examples in Pascal of Preparing a Statement with Dynamic Parameters
The following example uses a string as a parameter of the PREPARE
statement:
EXEC SQL PREPARE CMD FROM 'INSERT INTO PurchDB.Parts (PartNumber,PartName)
VALUES (?,?);';
In the following example, a host variable is used:
In the declare section, declare a host variable large enough to hold the string:
EXEC SQL BEGIN DECLARE SECTION;
:
DynamicCmdLine:string[80];
:
EXEC SQL END DECLARE SECTION;
:
Assign the string to the host variable:
DynamicCmdLine := 'INSERT INTO PurchDB.Parts (PartNumber, PartName)'+
' VALUES (?,?);';
Prepare the statement:
EXEC SQL PREPARE CMD1 FROM :DynamicCmdLine;