Wednesday, December 26, 2012
1Z0-895 Java Platform, Enterprise Edition 6 Enterprise JavaBeans Developer Certified Expert Exam
I passed in Oracle EJB Developer certification.
I studied the book EJB 3 In Action (http://www.amazon.com/EJB-3-Action-Debu-Panda/dp/1933988347). No need to study JPA chapters. The problem with this book is that it is about EJB 3 only, so it is necessary to study EJB 3.1 topics in another sources. This book is not so good, but it is starting point.
After reading the book I started doing mocks. I used Enthuware (http://enthuware.com/index.php/mock-exams/oracle-certified-expert/oceejbd-ejb-6). It is excellent and very similar as the exam.
As doubts were emerging during the mock I studied JSR 318 (http://jcp.org/en/jsr/detail?id=318). The JSR is not good to be used as initial source of learning, it is not a teaching document, but it is the best source of information.
The study method I have adopted is to learn by repetition. I did the initial mock and four standards mocks. For every mock, I did it by the first time, after reviewed all questions and then retraced the mock. The first time the grade was always low, but repeating grade was high.
The time it takes to make the mock by the first time is around 2 hours. The review needs 3 to 4 hours because that's when you really study. Repeating the mock takes 1 hour because you are already dominating the subject. It is important not to memorize the answers, but rather try to explain them.
To cover all topics of exam is necessary to make all the 4 standards mocks because the distribution of the questions is not 100%.
When finished doing the mocks, redid the questions I never hit (neither the first nor the repetition) for all mocks. It has a feature for this in Enthuware software.
I passed with 90% and I was pleased with the time spent to study.
Good luck in your studies.
How to limit the number of records returned in a SQL query
There is no a SQL standard to limit the number of records returned in a query, ie, each vendor implements this functionality in its own way.
Here's a summary on how to do this for some vendors:
DB2 -- select * from table fetch first 10 rows only
Informix, InterBase/Firebird, SKIP -- select first 10 * from table
Microsoft SQL Server and Access -- select top 10 * from table
MySQL, PostgreSQL, SQLite, HSQL/H2 -- select * from table limit 10
Oracle -- select * from table where rownum <= 10
Oracle Note:
If the query has "group by" or "order by" rownum must be supplied:
Ex:
SELECT a, b, c
FROM
( SELECT a, b, c, ROWNUM rn
FROM
( SELECT a, b, c FROM RECORD
WHERE AVAIL='Y"
ORDER BY DATE DESC
)
WHERE ROWNUM <= 25
)
WHERE rn >= 21;
FROM
( SELECT a, b, c, ROWNUM rn
FROM
( SELECT a, b, c FROM RECORD
WHERE AVAIL='Y"
ORDER BY DATE DESC
)
WHERE ROWNUM <= 25
)
WHERE rn >= 21;
References:
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