Defining and Manipulating Data

You embed data definition and data manipulation commands in a subprogram unit.

Data Definition

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

   ALTER TABLE                      DROP DBEFILE

   CREATE DBEFILE                   DROP DBEFILESET

   CREATE DBEFILESET                DROP GROUP

   CREATE GROUP                     DROP INDEX

   CREATE INDEX                     DROP MODULE

   CREATE TABLE                     DROP TABLE

   CREATE VIEW                      DROP VIEW

In a program, 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

   1                  ON PurchDB.Parts (PartName)

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

    EXEC SQL SELECT  PartName

   1           INTO :PartName

   2           FROM  PurchDB.Parts

   3          WHERE  PartName LIKE :partialkey

Data Manipulation

SQL has 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 single rows, insert single rows, or delete or update a limited number of rows.
Processing with cursors: 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 selected rows.
Dynamic operations: operations specified by the user or program at runtime.

In all 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 explained 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

   1           INTO :PartNumber,

   2                :PartName

   3                :SalesPrice :SalesPriceInd

   4           FROM  PurchDB.Parts

   5          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)

   1           INTO :PART-COUNT

   2           FROM  PurchDB.Parts

   3          WHERE  SalesPrice > :SalesPrice

All host variables used in a program unit must be declared in the Type Declaration Section in that program unit, as discussed earlier in this chapter under "Declaring Host Variables".

Defining and Manipulating Data

Technical documentation

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Data Definition

Data Manipulation