200+ SQL Developer Interview Questions and Answers

A change request in an application is serviced by the development team through various stages such as business analysis, code analysis, discussion with BA, and requirement freeze.

• The development team starts by analyzing the change request to understand its impact on the application.

• They perform business analysis to determine the feasibility and potential risks of implementing the change.

• Code analysis is conducted to assess the impact on existing code and identify any necessar...read more

Procedure to return a series (99, 96, 93, ...., 6, 3)

• Create a temporary table with a single column

• Use a loop to insert values into the temporary table

• Return the values from the temporary table in descending order

Use SQL JOIN to combine two tables and display information.

• Use the JOIN keyword to combine tables based on a related column

• Specify the columns you want to display in the SELECT statement

• Use ON clause to specify the column used for joining the tables

The result sets of all types of joins in SQL

• Inner Join: Returns only the matching rows from both tables

• Left Join: Returns all the rows from the left table and the matching rows from the right table

• Right Join: Returns all the rows from the right table and the matching rows from the left table

• Full Outer Join: Returns all the rows from both tables, including the unmatched rows

• Cross Join: Returns the Cartesian product of both tables

Query optimization techniques and types of schemas

• Query optimization techniques include indexing, query rewriting, and partitioning

• Schemas include user-defined, system-defined, and temporary schemas

• User-defined schemas are created by users to organize database objects

• System-defined schemas are created by the database management system

• Temporary schemas are used for temporary storage of data

• Differences between schemas include ownership, accessibility, and visibility

A Database Management System (DBMS) is a software that manages and organizes data in a structured manner.

• DBMS is used to create, retrieve, update, and delete data in a database.

• It provides a way to store, manage, and manipulate large amounts of data efficiently.

• DBMS ensures data integrity, security, and concurrency control.

• Examples of popular DBMS include MySQL, Oracle, SQL Server, and PostgreSQL.

To delete records in a table, use the DELETE statement with the WHERE clause to specify the condition for deletion.

• Use the DELETE statement followed by the table name

• Add the WHERE clause to specify the condition for deletion

• Execute the query to delete the records

I have 5 years of experience in SQL. My last project involved optimizing database queries for a large e-commerce platform.

• 5 years of experience in SQL

• Optimized database queries for a large e-commerce platform

• Worked on improving performance and efficiency of database operations

SQL is a programming language used for managing and manipulating relational databases.

• SQL stands for Structured Query Language.

• It is used to communicate with and manipulate databases.

• SQL can be used to create, modify, and retrieve data from databases.

• It is a standard language for relational database management systems (RDBMS).

SQL is a standard language for managing databases, while MySQL is a specific open-source relational database management system.

• SQL is a standard language used to manage databases, while MySQL is a specific implementation of SQL.

• SQL is an ANSI (American National Standards Institute) standard, while MySQL is an open-source relational database management system.

• SQL can be used with various database management systems like Oracle, SQL Server, etc., while MySQL is a specific datab...read more

Functions and procedures are both stored database objects used to perform specific tasks in SQL.

• Functions return a value while procedures do not.

• Functions can be used in SQL statements, whereas procedures cannot.

• Functions can have input parameters and return a single value, while procedures can have input and output parameters.

• Functions are typically used for calculations or data manipulation, while procedures are used for executing a series of SQL statements.

• Examples of func...read more

Job security in Avendata Gmbh is good.

• Avendata Gmbh has a stable and growing business.

• The company has a diverse range of clients and projects.

• Avendata Gmbh invests in employee training and development.

• The company has a positive work culture and values its employees.

• There have been no recent reports of layoffs or downsizing.

Query to retrieve employee details with maximum salary in each department

• Use a subquery to get the maximum salary for each department

• Join the subquery with the main employee table to retrieve employee details

• Display employee details along with their respective salaries

Print numbers in pyramid shape patterns using SQL code.

• Use a loop to iterate through rows and columns to print the numbers in pyramid shape.

• Increment the numbers in each row to create the pyramid effect.

• Consider the spacing and alignment to create a visually appealing pyramid pattern.

Views are virtual tables that display data from one or more tables, while stored procedures are a set of SQL statements that perform a specific task.

• Views are used to simplify complex queries by storing them as a virtual table.

• Views do not store data themselves, but rather display data from underlying tables.

• Stored procedures are precompiled sets of SQL statements that can be executed with parameters.

• Stored procedures can perform tasks such as data manipulation, validation, a...read more

SQL is a programming language used for managing data in relational databases. Window functions are used for calculations within a specific window of rows. Joins are used to combine data from multiple tables based on a related column.

• SQL stands for Structured Query Language and is used for managing data in relational databases

• Window functions in SQL allow for calculations to be performed within a specific window of rows

• Examples of window functions include ROW_NUMBER(), RANK(),...read more

Rank and Dense_Rank are window functions used to assign a rank to each row based on a specific column value.

• Rank assigns unique ranks to each row based on the column value.

• Dense_Rank assigns ranks to each row based on the column value, but skips the rank if there are ties.

• Both functions are used with the OVER() clause and ORDER BY statement.

• Example: SELECT name, salary, RANK() OVER(ORDER BY salary DESC) AS rank FROM employees;

• Example: SELECT name, salary, DENSE_RANK() OVER(OR...read more

Cursors are database objects used to retrieve, manipulate, and navigate through a result set row by row.

• Cursors allow for row-by-row processing of SQL results.

• Types of cursors: implicit and explicit.

• Example of creating an explicit cursor: DECLARE cursor_name CURSOR FOR SELECT column_name FROM table_name;

• To fetch data from a cursor: FETCH cursor_name INTO variable_name;

• An alternate way to process rows is using a WHILE loop.

In MS SQL Server, concatenation is done using the + symbol.

• MS SQL Server does not have a CONCAT function

• Use the + symbol to concatenate strings

• Example: SELECT 'Hello' + ' ' + 'World' AS Greeting

List is a collection of objects, string array is an array of strings, etc. Each has its own characteristics and uses.

• List: dynamic collection of objects, can grow/shrink in size. Example: List<Integer> numbers = new ArrayList<>();

• String array: fixed-size array containing strings. Example: String[] names = new String[3];

• Array: fixed-size collection of elements of the same type. Example: int[] scores = new int[5];

Join is used to combine rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables.

• Syntax: SELECT column_name(s) FROM table1 JOIN table2 ON table1.column_name = table2.column_name;

• Types of joins: INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, CROSS JOIN.

• Example: SELECT customers.name, orders.order_date FROM customers JOIN orders ON customers.customer_id = orders.customer_id;

Dense Rank and Rank are SQL functions used to assign a rank to each row in a result set based on a specified criteria.

• Dense Rank assigns unique ranks to each row, leaving no gaps in the ranking sequence.

• Rank assigns ranks to each row, leaving gaps in the ranking sequence.

• Both functions can be used with the OVER clause to partition the result set and order the ranking based on specific columns.

• Dense Rank and Rank are commonly used in scenarios like leaderboard rankings, top N ...read more

AS is used to assign an alias to a column or table in SQL, while IS is used to compare values or check for null values.

• AS is used in SELECT statements to assign a temporary name to a column or table

• AS can also be used in JOIN statements to assign aliases to tables

• IS is used in WHERE clauses to compare values or check for null values

• IS NULL is used to check if a value is null

• IS NOT NULL is used to check if a value is not null

SQL code to find Nth maximum salary department wise.

• Use the RANK() function to assign a rank to each salary within each department.

• Filter the results to only include the rows where the rank is equal to N.

• Group the results by department to get the Nth maximum salary department wise.

Understanding SQL joins, group by, having, and where clauses for effective data querying.

• Joins combine rows from two or more tables based on a related column. Example: SELECT * FROM table1 JOIN table2 ON table1.id = table2.id;

• GROUP BY aggregates data across specified columns. Example: SELECT department, COUNT(*) FROM employees GROUP BY department;

• HAVING filters groups created by GROUP BY. Example: SELECT department, COUNT(*) FROM employees GROUP BY department HAVING COUNT(*) ...read more

Primary key uniquely identifies each record in a table, while unique key ensures each value in a column is unique.

• Primary key does not allow NULL values, while unique key allows one NULL value.

• A table can have only one primary key, but multiple unique keys.

• Primary key automatically creates a unique index, while unique key does not.

• Primary key is used to establish relationships between tables, while unique key is used to enforce data integrity.

To extract execution plan of a SQL query, use EXPLAIN or SHOW PLAN command.

• Use EXPLAIN or SHOW PLAN command before the SQL query

• EXPLAIN command shows the execution plan in a tabular format

• SHOW PLAN command shows the execution plan in a graphical format

• Execution plan helps in optimizing the query for better performance