HP 3000 Manuals

ALLBASE/SQL Pascal Application Programming Guide

Defining and Manipulating Data 

You embed data definition and data manipulation commands in statement
parts.

Data Definition 

You can embed the following SQL commands to create objects or change
existing objects:

     ALTER DBEFILE             CREATE INDEX            DROP GROUP
     ALTER TABLE               CREATE TABLE            DROP INDEX
     CREATE DBEFILE            CREATE VIEW             DROP MODULE
     CREATE DBEFILESET         DROP DBEFILE            DROP TABLE
     CREATE GROUP              DROP DBEFILESET         DROP VIEW

Data definition commands are useful for such activities as creating
temporary tables or views to simplify data manipulation or creating an
index that improves the program's performance:

     EXEC SQL CREATE INDEX PartNameINDEX
                        ON Purchdb.Parts (PartName);

The index created with this command expedites data access operations
based on partial key values:

     EXEC SQL SELECT PartName
               INTO :PartName
                FROM Purchdb.Parts
               WHERE PartName LIKE :PartialKey;

Data Manipulation 

SQL has the following four basic data manipulation commands:

   *   SELECT - Retrieves data.

   *   INSERT - Adds rows.

   *   DELETE - Deletes rows.

   *   UPDATE - Changes column values.

These four commands can be used for various types of data manipulation
operations:

   *   Simple data manipulation:  operations that retrieve a single row,
       insert a single row, or delete or update a limited number of rows.

   *   Sequential table processing:  operations that use a cursor to
       operate on a row at a time within a set of rows.  A cursor is a
       pointer the program advances through the set of rows.

   *   Bulk operations:  operations that manipulate multiple rows with a
       single execution of a data manipulation command.

   *   Dynamic operations:  operations specified by the user at run time.

In all non-dynamic data manipulation operations, you use host variables
to pass data back and forth between your program and the DBEnvironment.
Host variables can be used in the data manipulation commands wherever the
syntax in the ALLBASE/SQL Reference Manual allows them.

The SELECT command shown at 8 in Figure 3-1 retrieves the row from
PurchDB.Parts that contains a part number matching the value in the host
variable named in the WHERE clause (PartNumber).  The three values in the
row retrieved are stored in three host variables named in the INTO clause
(PartNumber, PartName, and SalesPrice).  An indicator variable
(SalesPriceInd) is also used in the INTO clause, to flag the existence of
a null value in column SalesPrice:

     EXEC SQL SELECT  PartNumber, PartName, SalesPrice
                INTO :PartNumber,
                     :PartName,
                     :SalesPrice  :SalesPriceIND 
                FROM  Purchdb.Parts
               WHERE  PartNumber = :PartNumber;

You can also use host variables in non-SQL statements; in this case, omit
the colon:

      SalesPrice := Response;
     EXEC SQL SELECT  COUNT(PartNumber)
                INTO :PartCount
                FROM  Purchdb.Parts
               WHERE  SalesPrice > :SalesPrice;

All host variables used in procedures must be declared in a declaration
part, as discussed earlier in this chapter under "Declaring Host
Variables".

MPE/iX 5.0 Documentation