Case Studies

3.1 Case Descriptions

The cases illustrate:

A simple query (Case 1)
A more complex query (Case 2)
Joining SQL Server tables (Case 3)
Write capabilities (Case 4)
A data dictionary query (Case 5)
The pass-through feature (Case 6)
Executing stored procedures (Case 7)

3.2 Installation Media Contents

The installation media contains the following:

Demonstration files
One SQL script file that creates the demonstration tables and stored procedures in the SQL Server database
One SQL script file that drops the demonstration tables and stored procedures from the SQL Server database

3.3 Demonstration Files

After a successful gateway installation, use the demonstration files stored in the directory ORACLE_HOME\dg4msql\demo where ORACLE_HOME is the directory under which the gateway is installed. The directory contains the following demonstration files:

bldmsql.sql
case1.sql
case2.sql
case3.sql
case4a.sql
case4b.sql
case4c.sql
case5.sql
case6a.sql
case6b.sql
case7.sql
dropmsql.sql

3.4 Demonstration Requirements

The case studies assume these requirements have been met:

The gateway demonstration tables and stored procedures are installed in the SQL Server database
The Oracle database has an account named SCOTT with a password of TIGER
The Oracle database has a database link called GTWLINK (set up as public or private to the user SCOTT) which connects the gateway to a SQL Server database as SCOTT with password TIGER2

For example, you can create the database link as follows:
```
SQL> CREATE DATABASE LINK GTWLINK CONNECT TO SCOTT
  2    IDENTIFIED BY TIGER2 USING 'GTWSID';
```
Oracle Net Services is configured correctly and running

3.5 Creating Demonstration Tables

The case studies are based on the GTW_EMP, GTW_DEPT, and GTW_SALGRADE tables and the stored procedures InsertDept and GetDept. If the demonstration tables and stored procedures have not been created in the SQL Server database, use the bldmsql.sql script to create them. Enter the following:

> isql -USCOTT -PTIGER2 -ibldmsql.sql

The script creates the demonstration tables and stored procedures in the SQL Server database accordingly:

CREATE TABLE GTW_EMP (
EMPNO      SMALLINT NOT NULL 
ENAME      VARCHAR(10),
JOB        VARCHAR(9),
MGR        SMALLINT,
HIREDATE   DATETIME,
SAL        NUMERIC(7,2),
COMM       NUMERIC(7,2),
DEPTNO     SMALLINT)
go

CREATE TABLE GTW_DEPT (
DEPTNO     SMALLINT NOT NULL,
DNAME      VARCHAR(14),
LOC        VARCHAR(13)) 
go

CREATE TABLE GTW_SALGRADE (
GRADE      MONEY,
LOSAL      NUMERIC(9,4),
HISAL      NUMERIC(9,4))
go

DROP PROCEDURE InsertDept
go

CREATE PROCEDURE InsertDept (@dno INTEGER,
   @dname VARCHAR(14), @loc VARCHAR(13))
AS INSERT INTO GTW_DEPT VALUES (@dno, @dname, @loc)
go

DROP PROCEDURE GetDept
go

CREATE PROCEDURE GetDept (@dno INTEGER, @dname VARCHAR(14) OUTPUT)
AS SELECT @dname=DNAME FROM GTW_DEPT WHERE DEPTNO=@dno
go

3.5.1 Demonstration Table Definitions

The following table definitions use information retrieved by the SQL*PLUS DESCRIBE command:

GTW_EMP

Name                            Null?    Type
------------------------------- -------- ----
EMPNO                           NOT NULL NUMBER(5)
ENAME                                    VARCHAR2(10)
JOB                                      VARCHAR2(9)
MGR                                      NUMBER(5)
HIREDATE                                 DATE
SAL                                      NUMBER(7,2)
COMM                                     NUMBER(7,2)
DEPTNO                                   NUMBER(5)

GTW_DEPT

Name                            Null?    Type
------------------------------- -------- ----
DEPTNO                          NOT NULL NUMBER(5)
DNAME                                    VARCHAR2(14)
LOC                                      VARCHAR2(13)

GTW_SALGRADE

Name                            Null?    Type
------------------------------- -------- ----
GRADE                                    NUMBER(19,4)
LOSAL                                    NUMBER(9,4)
HISAL                                    NUMBER(9,4)

3.5.2 Demonstration Table Contents

The contents of the SQL Server tables are:

GTW_EMP

EMPNO ENAME   JOB         MGR   HIREDATE   SAL   COMM   DEPTNO
----- -----   ---         ---   --------   ---   ----   ------
7369  SMITH   CLERK       7902  17-DEC-80   800             20
7499  ALLEN   SALESMAN    7698  20-FEB-81  1600   300       30
7521  WARD    SALESMAN    7698  22-FEB-81  1250   500       30
7566  JONES   MANAGER     7839  02-APR-81  2975             20
7654  MARTIN  SALESMAN    7698  28-SEP-81  1250  1400       30
7698  BLAKE   MANAGER     7839  01-MAY-81  2850             30
7782  CLARK   MANAGER     7839  09-JUN-81  2450             10
7788  SCOTT   ANALYST     7566  09-DEC-82  3000             20
7839  KING    PRESIDENT         17-NOV-81  5000             10
7844  TURNER  SALESMAN    7698  08-SEP-81  1500     0       30
7876  ADAMS   CLERK       7788  12-JAN-83  1100             20
7900  JAMES   CLERK       7698  03-DEC-81   950             30
7902  FORD    ANALYST     7566  03-DEC-81  3000             20
7934  MILLER  CLERK       7782  23-JAN-82  1300             10

GTW_DEPT

DEPTNO DNAME          LOC 
----- -------------- --------
   10 ACCOUNTING     NEW YORK
   20 RESEARCH       DALLAS
   30 SALES          CHICAGO
   40 OPERATIONS     BOSTON

GTW_SALGRADE

GRADE      LOSAL      HISAL
------     ------     -----
    1        700      1200
    2       1201      1400
    3       1401      2000
    4       2001      3000
    5       3001      9999

3.6 Case 1: Simple Queries

Case 1 demonstrates the following:

A simple query
A simple query retrieving full date information

The first query retrieves all the data from GTW_DEPT and confirms that the gateway is working correctly. The second query retrieves all the data from GTW_EMP including the time portion of the hire date because the default date format was set to DD-MON-YY HH24:MM:SS for the session by an ALTER SESSION command.

3.7 Case 2: A More Complex Query

Case 2 demonstrates the following:

The functions SUM(expression) and NVL(expr1, expr2) in the SELECT list
The GROUP BY and HAVING clauses

This query retrieves the departments from GTW_EMP whose total monthly expenses are higher than $10,000.

3.8 Case 3: Joining SQL Server Tables

Case 3 demonstrates the following:

Joins between SQL Server tables
Subselects

The query retrieves information from three SQL Server tables and relates the employees to their department name and salary grade, but only for those employees earning more than the average salary.

3.9 Case 4: Write Capabilities

Case 4 is split into three cases and demonstrates the following:

3.9.1 DELETE Statement

Case 4a demonstrates bind values and subselect. All employees in department 20 and one employee, WARD, in department 30 are deleted.

3.9.2 UPDATE Statement

Case 4b provides an example of a simple UPDATE statement. In this example, employees are given a $100 a month salary increase.

3.9.3 INSERT Statement

Case 4c is an example of a simple insert statement that does not provide information for all columns.

3.10 Case 5: Data Dictionary Query

Case 5 demonstrates data dictionary mapping. It retrieves all the tables and views that exist in the SQL Server database that begin with GTW.

3.11 Case 6: The Pass-Through Feature

Case 6 demonstrates the gateway pass-through feature which allows an application to send commands or statements to SQL Server.

This case demonstrates:

A pass-through UPDATE statement using bind variables
A pass-through SELECT statement

3.11.1 UPDATE Statement

Case 6a provides an example of a pass-through UPDATE statement with bind variables. In this example, the salary for EMPNO 7934 is set to 4000.

3.11.2 SELECT Statement

Case 6b provides an example of a pass-through SELECT statement. The data that is returned from the SELECT statement is inserted into a local table at the Oracle database.

3.12 Case 7: Executing Stored Procedures

Case 7 demonstrates the gateway executing a stored procedure in the SQL Server database.