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30 nov

How To: Hire an OracleDB Developer

While Oracle Database isn’t as widely used as SQL databases, there are plenty of reasons to hire an OracleDB Developer. Oracle Database, for example, is the first database designed for enterprise grid computing, has exceptionally advanced partitioning implementation and optimizer, and more.

If you’re deciding whether or not to look for an OracleDB Developer for hire, check out some of the benefits of using OracleDB. Then, we’ll show you the best OracleDB interview questions for 2018, so you can be confident that you’re getting a real expert to manage your data.

 

Why hire an OracleDB Developer

Enterprise Grid Computing

This type of computing helps you manage your data and applications in a cost-effective and flexible way and “creates large pools of industry-standard, modular storage, and servers.” One of the reasons that this type of architecture functions so well is that each new system can be “rapidly provisioned from the pool of components.”

A primary benefit of OracleDB, then, is that capacity can simply be added or reallocated when necessary from the resource pools, eliminating the need for peak workloads. Additionally, the way that the logical and physical structures are separated in an OracleDB means that you can manage the physical storage of the data without changing the logical storage structures’ access.

 

Customization and Organization

If you want to hire an OracleDB developer, an expert will be able to customize this database more than many other types of storage systems. If you’re looking at OracleDB in comparison with MySQL, Oracle gives many more opportunities to fit the database and hardware to the specific solution that is best for your business, with more variability and design choices.

OracleDB also allows you to reuse code that interacts with data objects and helps its developers write clean code, whereas MySQL developers write their code outside of the database, giving them slightly less control.

Additionally, Oracle database gives its users plenty of instrumentation to fully understand what is going on inside of your software and hardware, allowing you to adjust more settings to your OracleDB developer’s particular needs and liking.

Beyond this, Platform as a Service (PaaS) work is straightforward in OracleDB because of the advanced partitioning and subpartitioning implementation offered, giving plenty of options to specify your business solutions.

One of the last significant benefits of OracleDB is that its advanced optimizer can model data in many different ways, including nested subqueries and recursive queries.

 

Some disadvantages of using OracleDB

Even with all the benefits, there are some reasons you might not want to use OracleDB. First off, it’s got a rather steep learning curve that doesn’t compare to its competitor MySQL. While you certainly need an expert with both types of databases, it’s even more important to find an expert to use Oracle.

Luckily for you, we highly vet developers from around the world and only send you the best. Then, you can use these useful OracleDB interview questions to confirm their expertise. Otherwise, you risk hiring a developer that doesn’t fully understand what they’re doing.

Another negative of OracleDB is that it isn’t free and costs more than many of its competitors. However, many users find that its advantages outweigh the cost savings that they could have from other databases.

 

Best OracleDB Interview Questions for 2018

Explain SAVEPOINT and give an example

In Oracle, you can name and mark your current spot in the transaction’s processing with the SAVEPOINT statement. All savepoints will be erased with a simple rollback or commit. Additionally, “when you roll back to a savepoint, any savepoints marked after that savepoint are erased,” although the one that you roll back does remain.

Your OracleDB developer for hire should also know that they can use savepoints to undo parts of a transaction rather than the whole thing with the ROLLBACK TO statement. Savepoint names can be reused; this simply makes the savepoint move from its old position to the point in which it’s renamed.

OracleDB marks savepoints implicitly before executing an INSERT, UPDATE, or DELETE statement. Then, if the statement happens to fail, the database automatically performs a rollback to this implicit savepoint.

Typically though, the whole transaction isn’t rolled back; instead, just the failed SQL statement. Your OracleDB developer has to understand SAVEPOINT, both when used explicitly and implicitly, to guarantee that all work is properly saved and protected.

Oracle’s website gives an example of how to use SAVEPOINT with ROLLBACK below:

 

CREATE TABLE emp_name AS SELECT employee_id, last_name, salary FROM employees;
CREATE UNIQUE INDEX empname_ix ON emp_name (employee_id);

DECLARE
  emp_id        employees.employee_id%TYPE;
  emp_lastname  employees.last_name%TYPE;
  emp_salary    employees.salary%TYPE;
BEGIN
  SELECT employee_id, last_name, salary INTO emp_id, emp_lastname,
    emp_salary FROM employees WHERE employee_id = 120;
  UPDATE emp_name SET salary = salary * 1.1 WHERE employee_id = emp_id;
  DELETE FROM emp_name WHERE employee_id = 130;
  SAVEPOINT do_insert;
  INSERT INTO emp_name VALUES (emp_id, emp_lastname, emp_salary);
EXCEPTION
  WHEN DUP_VAL_ON_INDEX THEN
     ROLLBACK TO do_insert;
     DBMS_OUTPUT.PUT_LINE('Insert has been rolled back');
END;
/

Briefly, explain the OracleDB ANALYZE statement

The ANALYZE statement is a particularly useful one for any OracleDB developer to know. It collects or deletes statistics about a particular index or index partition, table or table partition, index-organized table, cluster, or scalar object attribute.

With this statement, you can also identify migrated and chained rows of a table or cluster as well as validate the structure of an index or index partition, table or table partition, index-organized table, cluster, or object reference (REF).

 

Explain a hash cluster in Oracle and give an example

The reason that your OracleDB developer should know about sorting tables in a hash cluster is because it’s used as an alternative to a non-clustered table with an index or an index cluster to improve the performance of data retrieval.

It works by physically storing the rows of a table in a hash cluster. Then, when you need to retrieve the data, it performs this action according to the results of a hash function. Hash values, which are numeric values, are generated by OracleDB’s hash function, are based on specific cluster key values.

A minimum of two I/Os is necessary to find or store a row in an indexed table or cluster, although they typically more than two. However, no I/O is required to locate a row in a hash cluster because the database utilizes a hash function; although, to read or write a row in a hash cluster, a minimum of one I/O operation is necessary.

According to Oracle, the most useful times to use a hash cluster are under the following conditions:

  • If the majority of queries on the cluster key are equality queries:

    SELECT … WHERE cluster_key = …;

  • You have static-sized tables in the hash cluster and can determine exactly how much space is required for the tables. One of the downfalls of tables in a hash cluster is that the performance can suffer if they require more space than what was initially allocated for the cluster.

 

Ask your OracleDB developer for hire to perform an example of creating a hash cluster. In the following example given by Oracle, trial_cluster is the name of the created cluster that holds the trial table. The trialno column is the cluster key, and the lower statement creates the table in the cluster.

 

CREATE CLUSTER trial_cluster (trialno NUMBER(5,0))
   TABLESPACE users
   STORAGE (INITIAL 250K     NEXT 50K
     MINEXTENTS 1     MAXEXTENTS 3
     PCTINCREASE 0)
   HASH IS trialno HASHKEYS 150;

CREATE TABLE trial (
   trialno NUMBER(5,0) PRIMARY KEY,
   ...)
   CLUSTER trial_cluster (trialno);

What is the difference between a hot backup and a cold backup with Oracle?

Of course, we all know that backups are vitally important for your information. Because of this, your OracleDB developer should know them very well. A cold backup is performed when the database is in a shutdown state, and there is no user activity currently on the system. This type of backup creates a full copy of the database, allowing you to fully restore it if necessary.

A hot backup, on the other hand, is taken while the database is active. This type of save provides you with an online backup with all files of the database copied. It doesn’t take care of active transactions, but there can be changes to the database during the copy.

 

So that's it - our best tips to hire an oracleDB developer! But you know what? Why go through all that trouble? We can do it for you - easy, painlessly. We'll take care of the evaluation and present you with three formidable candidates for your position, within two weeks - and you don't pay until you hire! Get in touch.