Introduction To Oracle Interview Questions And Answer
It’s a must for everyone to learn SQL. The demand for SQL is yet to decrease and SQL-expertise is highly valued in the market. There is a multitude of vendors providing database solutions with Oracle being the world’s most popular for executing OLTP (Online Transaction Processing) and DW (Data Warehousing).
So if you have finally found your dream job in Oracle but are wondering how to crack the Oracle Interview and what could be the probable Oracle Interview Questions for 2023. Every interview is different and the scope of a job is different too. Keeping this in mind we have designed the most common Oracle Interview Questions and answers for 2021 to help you get success in your interview.
In this article, we will cover most common 2023 Oracle Interview Questions that are mostly asked in an interview. These questions are divided into two parts are as follows:
Part 1 – Oracle Interview Questions (Basic)
This first part covers basic Oracle interview questions and answers
Answer:SELECT Name, YEAR(BirthDate) AS BirthYear FROM StudentDetails WHERE BirthYear >= 1998; This query will throw an error on the WHERE clause. Although an alias is specified in the SELECT clause it is not visible in the WHERE clause. The correct code can be written as follows:SELECT Name, YEAR(BirthDate) AS BirthYear FROM StudentDetails WHERE YEAR(BirthDate) >= 1998;
Answer: Semijoin returns records from the left table which match with the right table. Even if there are multiple matching records on the right table, the Semijoin returns a single record of the left table. It prevents duplications. Semijoin can be implemented using the WHERE EXISTS clause.
Answer: PL/SQL is a procedural language extension over SQL provided by Oracle. It facilitates declaration of variables, functions, and conditional operators in SQL syntax thereby giving the developer more freedom and ease to design complex queries.
Let us move to the next Oracle Interview Questions.
Answer: In PL/SQL, an error condition is called an exception and PL/SQL errors are handled using the EXCEPTION block. The syntax for handling exceptions is written below:DECLARE ... BEGIN ... EXCEPTION WHEN exception1 THEN ... WHEN exception2 THEN ... WHEN others THEN ... END;
Answer: This is the most common Oracle Interview Questions asked in an interview. Constraints are the rules defined over data. Named constraint for a primary key can be added in two ways: 1. During table creation:CREATE TABLE Employees ( Eid int NOT NULL, Name varchar(255) NOT NULL, Salary number(8), Age int, CONSTRAINT PK_ID PRIMARY KEY (Eid) ); 2. In the Alter statementALTER TABLE Employees ADD CONSTRAINT PK_ID PRIMARY KEY (Eid);
Answer: Savepoints are like markers. When executing a long transaction, it is a good programming practice to set up periodic savepoints so that we can roll back to the save point in case the transaction fails.
Let us move to the next Oracle Interview Questions.
Answer: BLOB is a binary large object datatype. It is used to stored unstructured data such as video, audio or . Maximum capacity of a BLOB is 4GB-1 in Oracle.
What is an index?
Indexes help speed up searching in a database. If there is no index on a column in the WHERE clause, then the SQL Server has to skim through the entire table and check each and every row to find matches, which may result in slow operations in large data.
Indexes are used to find all rows matching with some columns and then to skim through only those subsets of the data to find the matches.
Syntax: