Database Subsetting Tool
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This tutorial shows you how to export consistent sets of rows from relational databases into topologically sorted SQL-DML, i.e. a sequence of INSERT-statements ordered in a way that no foreign-key contraint will be violated during execution.

Objective

Exporting all the data related to the employee named 'Scott' into a SQL-script.

Step 1. Setup the database

Create a new database schema and execute script/scott-tiger.sql. Make sure that the script runs successfully.

$ db2 connect to wisser user wisser using <password>
$ db2 -tvf script/scott-tiger.sql

Step 2. Building the data model

Start the Tool (Jailer.exe or jailerGUI.bat on windows platform)

$ sh jailerGUI.sh

and create a new data model. Press New and enter "Tutorial" as the name for the new model.



A data model holds information about the tables in the database and all associations between them.
Most of the information can be retrieved automatically by analyzing the database schema.

Click on Analyze Database.
You will be asked for the database connection information.

Create a new connection.



Select the DBMS you are using from the displayed list, and fill out the following form:



Finally click on Connect. Jailer finds seven tables and five associations:




Two associations are still missing:

  • an employee is classified into a salary grade depending on his salary
  • employees may receive bonuses


Add the definitions manually (Add-Button under Associations):





The data model is now complete.

Step 3. Export employee Scott (unrestricted)

Now lets try to export the employee named Scott. To do that we need an extraction-model.
Select EMPLOYEE as table to extract from and type T.NAME='SCOTT' into the Where-field:




This extraction model describes a set of entities containing (the) employee(s) named 'SCOTT', entities associated with these employees, entities associated with these entities and so forth.

Export this set (Export Data-Button or Tools->Export Data). Jailer first asks for a file name for the new extraction model. Call it scott.csv. After that the Data Export dialog appears:





Type scott.sql into the first field. This defines the name of the export file to be generated.
Click on Export Data. The Progress Panel shows:




Jailer has generated a file scott.sql containing Insert-statements for Scott, for his boss, for the president and for scott's department, salary-grade and project participations.

But why are there also statements for all other employees?

Let Jailer explain why:




Open the Explain.log:





The data of Adams and James, for example, has been exported, because Scott (7788) is Adams (7876) boss and James (7900) and Adams are both classified in the same salary-grade.

Step 4. Export employee Scott (restricted)

Exporting an employee requires to export his boss and department too! Otherwise the set of exported entities would not be consistent (due to the dependencies based on foreign key constraints). No constraint prevents us from excluding the salary-grade and the bonus from export, but we don't do that becauses the resulting set would be incomplete.

On the other hand, we don't want to export all subordinates of an employee, or all employees who works in the same department as Scott.

To exclude subordinates, department-members and 'same salary-grade'-employees, we must restrict some associations.

A restriction is an extension of the associations join-condition (in SQL-syntax) for one direction of an association. disabled (or false) stands for an unsatisfiable condition.

Define restrictions:

  • from DEPARTMENT to EMPLOYEE
  • from EMPLOYEE to EMPLOYEE (inverse-BOSS)
  • from SALARYGRADE to EMPLOYEE
  • from PROJECT to PROJECT_PARTICIPATION
  • from ROLE to PROJECT_PARTICIPATION





Use Tools->Export Data again. Jailer will now export only the data related with Scott.

scott.sql
-- generated by Jailer at Sat May 03 12:38:33 CEST 2008  from wisser@desktop
--
-- extraction model:  EMPLOYEE where NAME='SCOTT' (extractionmodel/scott.csv)
-- database URL:      jdbc:db2://localhost/wisser
-- database user:     scott
-- Exported Entities: 13
--     DEPARTMENT                     2
--     EMPLOYEE                       3
--     PROJECT                        2
--     PROJECT_PARTICIPATION          2
--     ROLE                           2
--     SALARYGRADE                    2



Insert into SALARYGRADE(GRADE, LOSAL, HISAL) values (4, 2001, 3000), (5, 3001, 9999);
Insert into ROLE(ROLE_ID, DESCRIPTION) values (100, 'Developer'), (102, 'Project manager');
Insert into PROJECT(PROJECTNO, DESCRIPTION, START_DATE, END_DATE) values (1001, 'Development of Novel Magnetic Suspension System', '2006-01-01', '2007-08-13'), (1003, 'Foundation of Quantum Technology', '2007-02-24', '2008-07-31');
Insert into DEPARTMENT(DEPTNO, NAME, LOCATION) values (20, 'RESEARCH', 'DALLAS'), (10, 'ACCOUNTING', 'NEW YORK');
Insert into EMPLOYEE(EMPNO, NAME, JOB, BOSS, HIREDATE, SALARY, COMM, DEPTNO) values (7839, 'KING', 'PRESIDENT', null, '1981-11-17', 5000.00, null, 10);
Insert into EMPLOYEE(EMPNO, NAME, JOB, BOSS, HIREDATE, SALARY, COMM, DEPTNO) values (7566, 'JONES', 'MANAGER', 7839, '1981-04-02', 2975.00, null, 20);
Insert into EMPLOYEE(EMPNO, NAME, JOB, BOSS, HIREDATE, SALARY, COMM, DEPTNO) values (7788, 'SCOTT', 'ANALYST', 7566, '1982-12-09', 3000.00, null, 20);
Insert into PROJECT_PARTICIPATION(PROJECTNO, EMPNO, START_DATE, END_DATE, ROLE_ID) values (1003, 7566, '2007-02-24', '2008-07-31', 102);
Insert into PROJECT_PARTICIPATION(PROJECTNO, EMPNO, START_DATE, END_DATE, ROLE_ID) values (1001, 7788, '2006-05-15', '2006-11-01', 100);