Introduction to PLSQL Interview Questions And Answers
In this PLSQL Interview Questions article, we are going to take a look at some of the most important and frequently asked questions on PLSQL. These questions have been carefully picked to help prospective candidates and interviewees measure their knowledge of the subject and prepare themselves for PLSQL interviews.
If you are looking for a job related to PLSQL, you need to prepare for the 2021 PLSQL Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important PLSQL Interview Questions and Answers, which will help you get success in your interview.
In this 2021 PLSQL Interview Questions article, we shall present the 10 most essential and frequently used PLSQL interview questions. These interview questions are divided into two parts are as follows:
Part 1 – PLSQL Interview Questions (Basic)
This first part covers basic PLSQL Interview Questions and Answers.
Q1. Provide some of the most notable characteristics of PL/SQL.
Answer:
Characteristics of PLSQL are as follows:
- PL-SQL has a Block-structured language.
- PL-SQL have Stored procedures which helps in better sharing of application.
- PL_SQL is Portable to all environments which support Oracle.
- PL-SQL provides Integration to all Oracle data dictionaries.
Q2. Mention a few schema objects which can be created using PL/SQL?
Answer:
Schema objects that can be created using PLSQL are the following:
- Stored procedures and functions
- Triggers
- Packages
- Cursors
Let us move to the next PLSQL Interview Questions.
Q3. Explain what do you understand by PL/SQL cursors?
Answer:
Oracle uses something called workspaces which executes the SQL commands. What it means is that when Oracle processes a SQL command, an area in the memory called Private SQL Area is opened. A cursor can be treated as an identifier for this area. Cursors allow programmers to give a name to this area and access the information stored here.
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Q4. Point out the steps that are needed to perform to use an explicit cursor?
Answer:
This is the common PLSQL Interview Questions asked in an interview. The steps which can be performed on explicit cursor are −
- DECLARE – This is used to assign a name to the cursor and then define the structure of the query that goes within it.
- OPEN – It can be used to execute the query generated above, the rows returned by the query after execution are available for fetching at a later stage.
- FETCH – It assigns values from the current row, called a cursor position, into a specified variable.
- CLOSE – This is used for releasing the memory space.
Q5. What do you understand by triggers and provide their uses?
Answer:
Triggers can be understood as blocks of code running whenever the criteria for a specific event are satisfied. They are hardcoded inside the PLSQL program, and they listen to events which are as follow:
- DML or database manipulation,
- DDL or database definition, and
- Database operation.
They can be coded within a view or table and also a database or scheme for which the given event belongs. There are many other uses of triggers as well. For example, they are used to generate column values upon activation. And, For event logging within the table activities such as auditing and creating table duplicates. Triggers are used for security, too; they can implement security authorization functions and handle invalid transactions.
Part 2 – PLSQL Interview Questions (Advanced)
Let us now have a look at the advanced PLSQL Interview Questions and Answers.
Q6. Mention a few of the schema objects that can be created using PL/SQL?
Answer:
A schema is defined as a user-owned set of schema objects, also as logical data structures. These schema objects types are classified as follows:
- Clusters
- Database triggers
- Database links
- Dimensions
- Indexes and index types
- External procedure libraries
- Java classes
- Java resources
- Java sources
- Object tables, object types, and object views
- Materialized views and materialized view logs
- Operators
- Stored functions, procedures, and packages
- Sequences
- Synonyms
- Views
- Tables and index-organized tables
Some other types of objects which are not contained within a schema are the following:
- Contexts
- Profiles
- Directories
- Roles
- Users
- Tablespaces
- Rollback segments
Q6. Define what do you understand by Commit, Rollback, and Savepoint in the context of PLSQL.
Answer:
- The COMMIT Statement finalizes to end the given transaction, and it sets all changes to permanent. A transaction in SQL is defined as any type of statement that the Oracle Database treats as one single block. This enables database users to see the updates are done and changes made by the transaction. The COMMIT statement deletes all the savepoints prior to the given transaction and then releases transaction locks.
- The ROLLBACK statement is the opposite ofo this and undoes the transaction’s changes with the commit. This is hence practically the opposite of the COMMIT Statement as mentioned. Any locks made earlier due to the transaction are released.
- The SAVEPOINT statement is used to set a restoration point part from other uses when the ROLLBACK Statement is used. This controls the bounds of the ROLLBACK Statement by reverting it to the SAVEPOINT set point created earlier.
Let us move to the next PLSQL Interview Questions.
Q8. Mention the different data types that are available in PL/SQL?
Answer:
PLSQL data types can be mainly divided into one of the following categories. This is because there are so many data types available in PLSQL generally, but most of the time, you will be using some of the popular ones.
- Numbers – its types are: INT, INTEGER, NUMBER, FLOAT, SMALLINT, REAL etc.
- Boolean – its type is BOOLEAN.
- Character or String – such as CHAR, CHARACTER, VARCHAR, VARCHAR2, RAW, NCHAR, NVARCHAR2, etc.
- Date Time –such as DATE, TIMESTAMP.
Q9. What do you mean by an exception in PL/SQL?
Answer:
This is the most popular PLSQL Interview Questions asked in an interview. Exceptions are nothing but manageable errors in a program. Errors handled by such exceptions are within the controlling bounds of the programmer. What it means is that they can repair the same, and PL/SQL provides features to catch these errors so that debugging can be done. It prevents the program to stop working.
There are two types of exceptions mainly –
- System Exceptions and
- User-Defined Exceptions.
System Exceptions are those such as no_data_found or too_many_rows.PLSQL already defines the set.
User-Defined Exceptions are those exceptions that the user defines to handle one or more particular errors.
Q10. Define what Overloaded Procedure is.
Answer:
An overloaded procedure is an important feature in PL/SQL. It enables the developer to re-use the existing procedure that carries the exact name by slightly varying the parameter structure, which could be the data type or parameter number. This is similar to the overloaded methods/functions in the fundamental programming framework. It also promotes uniformity and versatility of PL/SQL blocks by providing a specific name procedure.
An overloaded procedure is like a mechanism that allows the developer to reuse the same procedure name mentioned above for different subprograms. This should give a fair understanding to show the importance of an overloaded procedure. For more details, documentation or a quick start guide of Oracle can be visited where necessary examples and codes will be provided with an illustration.
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