HP 3000 Manuals

ALLBASE/SQL FORTRAN Application Programming Guide

Declaring Host Variables 

Variables used in SQL commands are known as host variables.  All host
variables used in either a main program unit or a subprogram unit must be
declared in the Type Declaration Section of the program unit where the
host variable is used.  The host variable declarations must be the last
declarations in the Type Declaration Section of the program unit which
contains the embedded SQL statements and must appear between the two
following SQL commands:

          EXEC SQL BEGIN DECLARE SECTION
           .
           .  Host variables are declared here 
           .  in FORTRAN variable type descriptions.
           .
          EXEC SQL END DECLARE SECTION

In Figure 3-1, host variable declarations start at 2.

You cannot put more than one such declaration section in a program unit.
In addition, you must include the BEGIN DECLARE SECTION and END DECLARE
SECTION commands even if there are no host variables used in the embedded
SQL commands.  This is because the preprocessor includes the variable
declaration file after the END DECLARE SECTION command.

The SELECT command shown at 8 in Figure 3-1 uses three host variables for
data, one for each of the columns in the PurchDB.Parts table.  When used
in an embedded SQL command, host variables are preceded with a colon:

     :PartNumber
     :PartName
     :SalesPrice

Because these host variables are for data from a DBEnvironment, the
variable types must be compatible with the ALLBASE/SQL data stored in the
respective columns:

     CHARACTER*16           PartNumber 
     CHARACTER*30           PartName 
     DOUBLE PRECISION       SalesPrice 
     SQLIND                 SalesPriceInd 

The host variable named SalesPrice is accompanied by a second host
variable, SalesPriceInd.  Known as an indicator variable, this host
variable is used to detect null values.  If column SalesPrice contains a
null value, ALLBASE/SQL returns a negative number to SalesPriceInd.  The
subprogram unit named DisplayRow examines the value in this indicator
variable to determine whether to display the announcement that a Sales 
Price is null or display the value in SalesPrice.

Indicator variables are declared at 2 in Figure 3-1 as SQLIND. SQLIND is
a special declaration reserved for indicator variables.

MPE/iX 5.0 Documentation