Oracle is a multinational technology corporation that provides a wide range of database software and technology, cloud solutions, engineered systems, and enterprise software products. The company is famous for the Oracle Database, a relational database management system used by enterprises to store and manage their data. The interview process for Oracle can vary depending on the position and the level of the role you are applying for. Whether you’re a beginner appearing for the first Oracle interview round or an experienced professional appearing for senior positions, our set of Oracle interview questions and answers will make you more confident. Prepare with our questions set, and appear the interview confidently.
Only one command at a time
Data source to be presented
SQL data was used to construct this application
Structures consist of
Queries and instructions based on DDL and DML
Includes processes, functions, and so forth.
While it is recommended
Performing data CRUD operations
Developing programs that show SQL-derived data
SQL may be incorporated into PL/SQL.
SQL cannot contain PL/SQL.
Expect to come across this popular question in Oracle interview questions and answers
SQL is an abbreviation for Structured Query Language. SQL is a programming language that is used to connect with a server in order to access, alter and control data.
SQL statements are classified into five categories.
An alias is a user-defined alternate name for a column or table. Alias heads appear in upper case by default in columns. To make the alias case-sensitive, enclose it in double quotation marks (" ") The "AS" keyword before the alias name simplifies the SELECT clause.
Select emp_name AS name from employee; (Here AS is a keyword and “name” is an alias).
A Literal is a string that can contain a character, a number, or a date and is not a column name or alias and is included in the SELECT list. Date and character literals must be surrounded by single quotation marks (' '), but numeric literals do not have to be.
As an example: Choose last_name||'is a'||job_id As "emp information" from the employee; ("is a" is a literal here).
Arithmetic operators (*, /, +, -)
Concatenation operators (||
is[NOT] NULL, LIKE, [NOT] IN
NOT Logical condition
AND logical condition
OR logical condition
SQL Functions are an extremely powerful SQL feature. SQL functions can accept parameters but must always return a value. 1
SQL functions are classified into two types:
1. Single-Row Functions: These functions work on a single row to return a single result.
Single-Row Function Types:
2. Multiple-Row Functions: These functions act on groups of rows to return a single result for each group of rows.
Multiple-Row Function Types:
In Java, the Java virtual machine controls the thread's life cycle. The following are the java thread states:
NEW denotes a newly established thread that has not yet begun execution. RUNNABLE is either running or ready to be executed, but it is awaiting resource allocation. BLOCKED is awaiting a monitor lock in order to enter or re-enter a synchronized block/method. If the thread scheduler has picked it, it is in the operating state. When the run() method of a thread terminates, it is said to be terminated or dead.
This is a frequently asked question in Oracle interview questions.
The javac command reads source files containing Java module, package, and type declarations and compiles them into class files that operate on the Java Virtual Machine. Annotations in Java source files and classes can also be processed by the javac command.
In Java, a Wrapper class is a type of class that offers a method for converting primitive data types into objects and vice versa. When a wrapper class is constructed, a new field is generated in which the primitive data types are stored.
You want to know how many users are defined in the password file, as well as what permissions those users have. How would you go about doing this?
One of the most frequently posed Oracle basic interview questions, be ready for it.
To acquire information about the existing users in the password file, use the "v$pwfile users" view. Run the SQL query below:
SELECT * FROM v$pwfile users in sql;
For each user in the password file, the query above will return four columns. USERNAME, SYSDBA, SYSOPER, and SYSASM are the column names.
In the Oracle database, the basic unit of data storage is the table. Data is organized into rows and columns.
To construct a new table, use the "CREATE TABLE" command.
In Oracle, a nested table is a data type that has columns for storing multi-valued properties. An whole sub table can be stored in a nested table.
There are more Oracle interview questions and answers related to this topic on net.
One or more tablespaces or logical storage units can be found in an Oracle database. These tablespaces hold all of the data in a database. Each tablespace is made up of one or more data files. The data files are physical entities that adhere to the operating system on which Oracle is installed.
The command "ANALYZE" lets the user to execute numerous operations on an index, table or cluster. It is beneficial to:
The merge statement enables for the subsequent combining of data from two tables. It chooses data from the source table and inserts/updates it in the target table based on the query condition. Merge is a helpful command in data warehouse systems.
|Criteria||Characteristics of an Oracle DBA|
The primary storage structures
Architecture, both logical and physical
Data is saved as
Data blocks, extents, segments, and tablespaces are all types of data structures.
You can learn more about DBA from our Oracle DBA interview questions and answers site.
Oracle is a corporation. Oracle is a database server that maintains data in a highly organized manner. It enables users to save and retrieve relevant data in a multi-user environment, allowing several users to access the same data at the same time. All of this is done while maintaining great performance. A database server also prevents unwanted access and provides effective failure recovery options. A standby database is a database replica that is formed by backing up a primary database.
A DBA can create new users, delete current users, and change any environment variables or rights granted to other users.
It's no surprise that this one pops up often in Oracle interview questions software engineer.
Because the backup is taken while the database is alive and operating, it is also known as an online backup. And when the backup can only take place when the database is shut down, it is referred to as Cold Backup, which is also known as Offline Backup.
Passwords for database users are saved in the database's data dictionary. When a user tries to log into the database, his or her username and password are compared to the values in the database. If the username and password match, the user is granted database access. The data dictionary is kept in the database and may be accessed as long as the database is open. The dictionary also contains administrator passwords.
The data dictionary would be inaccessible until the database was locked. Because one of the administrator's responsibilities is to restart a down database, they must be able to log in even if the database is locked. That's where the password file comes in. A password file is an operating system file that is kept on a separate disc from the database. It saves the login and password for users with SYSDBA or SYSOPER access. When the database is unavailable, administrators with particular privileges are authenticated using password files.
Data files contain all of the tables. The data file contains all of the data. The database data is stored in the data files. The data of relational database structures, such as tables and indexes, is physically stored in database data files.
Normalization is the process of organizing data in a database. This entails creating tables and developing relationships between them in accordance with rules aimed to secure data while also making the database more adaptable by eliminating redundancy and conflicting dependencies.
The recovery catalog is a database architecture that holds the metadata for data restoration and recovery activities that RMAN administers. A recovery catalog stores the metadata utilized by RMAN throughout the reinstallation and healing processes. Even if the target control file and its backups are deleted, the RMAN information remains in the recovery catalogue.
The benefits of utilizing a view in a table are as follows:
A common question in Oracle interview questions advanced, don't miss this one.
Oracle provides numerous methods for shutting down the database.
To instantly shut down a database, use the command SHUTDOWN with the IMMEDIATE argument.
Use the SHUTDOWN command with the ABORT clause:
A query is added to any view to define particular table rows and columns. A virtual table is a form of view. There are two sorts of views available: read-only and read-write.
A few limitations of DML operations on Views are as follows:
If the View contains the following conditions, you cannot DELETE a row:
If a View contains the following information, you cannot MODIFY it.
What exactly is PL/SQL? Why do we need PL/SQL rather than SQL? Describe your previous experience with PLSQL and what challenges did you experience when working with PL SQL, and how did you solve them?
You will get different answers on this topic from Oracle PL/SQL interview questions and answers on-site.
A staple in Oracle interview questions for experienced, be prepared to answer this one.
Triggers are similar to stored procedures, they are automatically triggered anytime when a DML operation is done on a table or view.
PL/SQL supports two different types of triggers.
Statement Level Trigger: A statement-level trigger executes the trigger body just once for the DML statement.
Row Level Trigger: A row-level trigger executes the trigger body for each row of DML statement. This is why we utilize each row clause and internally stored DML transaction in the trigger specification; these qualifiers: old, new, are also known as records type variables.
These qualifiers are utilized in the trigger specification as well as the trigger body.
When we use these qualifiers in trigger specifications, we cannot include ":" in the names of the qualifiers.
If to_char(sysdate, ‘DY)=’THU’
then raise a;
when a then
dbms_output. put_line(‘my exception raised on thursday’);
Output: On Thursday, I filed an exception.
These are the advantages of PL/SQL packages.
PL/SQL is a SQL extension that is used in Oracle. PL/SQL combines SQL's data manipulation strength with procedural language processing capabilities to construct super-powerful SQL queries. It utilizes SQL to tell the compiler what to do and a procedural method to tell it how to accomplish it.
TRANSLATE is used to replace a character with another character, whereas REPLACE is used to replace a character with a word.
In a small-to-medium-sized database system, a single DBA may be the sole individual handling all of these activities. In big business setups, the role is frequently shared among numerous DBAs designated Database Security Administrator or Database Tuning Expert, each with his or her specific area of specialization.
You may create a database using one of three tools:
This is the fundamental syntax for determining the indexes for a table in Oracle.
SELECT owner, index_name, tablespace_name, status Set pages Break on table_name on index_name column table_name column index_name column column_name select table_name, index_name, column_name from dba_ind_columns where table_owner order by table_name, index_name column_position
There is the possibility of several database context processes. They are known as "DBWn" in the operating system. This technique is responsible for storing "dirty" buffers on disk. When a server process has to update a data block, it reads it from disk into the buffer cache if it isn't already there, then updates the cache copy. As a result, a "dirty" block is an updated database block in the buffer cache.
VARCHAR and VARCHAR2 are Oracle data types that are used to hold variable-length character strings. Their distinctions are as follows:
RAW datatype are used to store variable-length binary data such as byte strings.
The distinction between RAW and VARCHAR2 datatype is that PL/SQL does not recognize this data type and so cannot perform any transformations when transferring RAW data to various systems. This sort of data can only be queried or added into a table.
Syntax: RAW (precision)
A Primary Key is used to uniquely identify each table row, whereas a Unique Key prohibits duplicate entries in a table column.
Here are a few distinctions:
In Oracle, we may determine the current date and time by using the SYSDATE command.
SELECT SYSDATE into CURRENT_DATE from dual;
Expect to come across this popular question in Oracle interview questions.
The GROUP BY clause is used to identify and group data in the query results by one or more columns. This clause is frequently used with aggregate functions like as COUNT, MAX, MIN, SUM, AVG and so on.
SELECT COLUMN_1, COLUMN_2 FROM TABLENAME WHERE [condition] GROUP BY COLUMN_1, COLUMN_2
If the columns and relative data types in the source tables are the same, the set operator allows the user to retrieve data from two or more tables at once.
On a higher level, there are two types of backup accessible in Oracle: physical and logical.
Backup files are copied from the hard drive, media, or tapes to the restoration site during the restoration process, and the database is then made operational.
Recovery includes an extra step of updating these data files using redo logs in order to restore changes that were not backed up.
Let us look at this through the lens of a situation.
On Friday at 11 p.m., a thorough backup of the database is performed.
At 7 a.m. on Saturday, the database crashed.
We can restore the missing files using the Restoration 11 PM complete backup. However, the data will not be recovered until Friday at 11 p.m., rather than Saturday at 7 a.m. To achieve the same result, redo logs may be used, bringing the database to the point of failure.
Oracle has introduced flashback technology to restore database object states from the past. It can also retrieve inadvertent modifications that were committed. The value of the UNDO RETENTION option determines recovery.
For example, if the UNDO_RETENTION parameter is set to 2 hours and a user deletes the data by accident at 11 a.m. with a commit done. Using FLASHBACK QUERY, he may then get these rows just until 1 PM.
Clustering is a component of grid architecture that focuses on a certain goal.
While a grid may or may not consist of numerous clusters, it does include a larger structure that allows for the sharing of storage systems, data resources and other resources across different geographical areas.
A cluster will have a single owner, however the grid might have several owners depending on how many clusters it houses.
There are two kinds of optimizers:
Actual parameters are variables or expressions that are referenced in a subprogram's parameter list.
Consider the following method call, which has two real arguments named empno and amt:
Variables defined in a subprogram specification and referenced in the subprogram body are known as formal parameters.
The method that follows declares two formal parameters, empid and amt:
PROCEDURE raise_sal(empid INTEGER, amt REAL) IS current_salary REAL;
Save Points are used to break a transaction into smaller parts. It allows you to roll back a portion of a transaction. Oracle Database allows for a maximum of 5 save points. When an error occurs, you can roll back to the point where the SAVEPOINT was stored.
Oracle is an IT Corporation specializing in providing software and hardware products, cloud services, and consulting services related to information technology. They provide multiple services. Some of their prominent services include database management systems (DBMS), cloud services, Enterprise Resource Planning (ERP), Customer Relationship Management (CRM), Human Capital Management (HCM), and Supply Chain Management (SCM), among many others. Between 2011 and 2020, Oracle's annual revenue increased from approximately $35 billion to around $39 billion, according to its annual reports. They hire for many high positions with lucrative salaries. Some of the most common designations they hire are Software Engineers and Developers, Cloud Architects and Engineers, Business and Functional Consultants, Database Administrators, and sales and marketing professionals, among many others. According to Glassdoor, the average salary of a software developer is $174,205/yr. And the average salary of a Business Development Consultant is $195,396/yr. If you want to upskill yourself in database administration, enroll in our Database Programming course. With our expert-curated Oracle interview questions and answers, you'll be well-prepared to crack any interview confidently.
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