Procedural Language Extensions to the Structured Query Language or PL/SQL is a block-structured language developed or designed by Oracle. Help the developers to merge the power of SQL with procedural statements. In this case, the oracle engine is used through every statement of a block passing through it at a time which enables to increase the speed along with it and also helps to decrease the traffic. It also contains the procedure characteristics of programming languages. In the year 1980, Oracle developed PL/SQL. Except the PL/SQL the other two important programming languages which are developed by Oracle are – SQL and Java. It is a complete portable as well as a high transaction processing performance language. It gives some in-built features that are interpreted and independent of the Operating System programming nature. The syntax of PL/SQL is dependent on ADA and Pascal programming language. Through this article, you will come to know what type of questions during the time of the interview. Let us know about that the PL/SQL Interview Questions.
Description
Very Frequently Asked Interview Questions
- What ate the Features of PL/SQL?
It has some features like its procedural environment helps to perform decision making, looping, and branching. At one block various queries can be processed just by using a single command. Exception-handling can also be done using PL/SQL.
- Define PL/SQL table?
Tables of PL/SQL contain objects of the type that are modeled as database sets. The table provides arrays; it is a temporary table used for faster processing. Bulk data is removed by using this.
- Describe the structure of PL/SQL?
It is a block structure. All the PL/SQL code consists of SQL. Statements of PL/SQL constitute a block of PL/SQL.
- Definition of the cursor of PL/SQL?
The cursor of PL/SQL is very similar to the pointer; it contains an area of memory for SQL statements. This memory is also known as the area of context. In other words, the cursor selects a row from the database then the selected lines are executed one by one through the program. Cursors are of two types—(i) Implicit and (ii) Explicit.
- Write the process on how to assign a name to an unnamed PL/SQL exception block?
Exception_INIT is used to assign a name to an unnamed PL/SQL exception block. With the help of this, a programmer can order the compiler to give the custom error text message based on the logic. It overrides the pre-defined message at the time of compilation.
- When is the DECLARE block is compulsory?
Anonymous blocks of PL/SQL are used as the DECLARE statement. It is like a non-stored and stand-alone procedure. In the stand-alone file, this statement will come first.
- Use of WHEN clause in a trigger?
It defines for what purpose the trigger is used.
- Distinguish between implicit and explicit cursor?
Implicit- (i) It is usually used when any query gives back the value of a single row.
(ii) It is used on certain operations such as DECLARE, FETCH, CLOSE and OPEN.
(iii) NO_DATA_FOUND exception handling is done here.
Explicit- (i) It is used in any case, a subquery gives back more than a single row.
(ii) To process more than one-row cursor is used.
(iii) NO_DATA_FOUND exception handling is not done here.
- What are the data types in PL/SQL?
Binary_Integer, BLOB, BLOB(n), BOOLEAN, CHAR, CHAR(n), CHAR VARYING(n), CHARACTER, CHARACTER(n), DATE, DECIMAL, DOUBLE, FLOAT, INT, INTEGER.
- What are the features of PL/SQL?
It is tightly joined with SQL.
Extensive checking of work offered.
Various kinds of data types are provided.
Various programming structures are provided.
Structural programming of procedures, functions, and object programming is supported.
Web application development and server pages supported on PL/SQL.
Some other features include- high performance, handling of error, high-quality performance, and much more.
- How to do commenting in PL/SQL?
Means avoiding a particular code that is not needed by the programmer. For, commenting on a specific line (‘….’) symbol was used. To commit multiple lines, we have to use (’/*…*/’)this symbol. The multiline commenting is very much similar to the C programming language.
- Write the simple and a basic syntax of PL/SQL.
DECLARE
<section of declaration>
BEGIN
<commands need to execute>
EXCEPTION
<part of exception handling>
END;
- Explain in brief about the structural block of PL/SQL?
It contains some structure defined at the time of its development into which the codes are a group. Sections of it are– declaration, execution, and exception handling section.
(i) The Declaration section is defined as an optional section that can be skipped when no declaration is required.
(ii) Execution section is the mandatory section without it the code will not work. Execute the code that is written into it.
(iii) Exception handling section is the last and mandatory section without it the program will not execute. It contains PL/SQL statements that work during run time.
- What is the purpose of the SYSDATE and USER keyword?
SYSDATE🡪 It is used to return the current time and date on the local database server. If we want to split a part of data, the TO_CHAR function is used on SYSDATE and describes the particular format we need.
USER🡪 It is used to get back the user Id of the current session.
- What are the differences between SQL and PL/SQL?
SQL— It is a natural language. It is used for Interactive processing of data in the database. We cannot do decision making or looping in SQL. It is a time-consuming process. Error handling mechanism is not supported by SQL.
PL/SQL—It is a procedural expansion of SQL. It supports every feature of procedural language. Looping and conditional statements are supported by it. Handling errors is possible.
- Distinguish between ROLLBACK and ROLLBACK TO in PL/SQL.
ROLLBACK—For rolling back of all the changes from the start of the transaction this command is used.
ROLLBACK TO—Purpose of it is to undo the transaction till a SAVEPOINT. Before the SAVEPOINT transaction cannot be rolled back, this is the reason why transactions remain on even before the specification of command.
- Why is SYS.ALL_ DEPENDENCIES used for?
For describing all the dependencies among the procedures, packages, triggers, functions that are accessible to the user who is currently using it, SYS.ALL_ DEPENDENCIES is used. It also helps to return the columns such as:: name, dependency_type, type, referenced_owner, etc.
Conclusion
It is one of the most demanded programming languages in the world. To start the coding DECLARE function is needed. If a student learns this language properly, then he/she can easily get a job in a company. This language is mainly used in packages, procedures, functions, and types. Too many questions are asked on PL/SQL during the interview.
Frequently Asked Questions
Which one is better among PL/SQL and SQL?
PL/SQL is an extended part of SQL.
Is PL/SQL easy to learn?
It is one of the most-easiest programming languages and is very easy to learn for a student.
Importance of PL/SQL?
It helps to update, transfer and query any dataset.
