10+ SQL and PL SQL Developer Interview Questions and Answers

SQL Loader is a tool used to load data from external files into Oracle database tables.

• SQL Loader is a command-line tool provided by Oracle for loading data from external files into Oracle database tables.

• It can handle large volumes of data efficiently and is commonly used for bulk data loading.

• SQL Loader uses control files to define the format of the data in the external file and the target table in the database.

• It is often used in data migration and data warehousing project...read more

Types of joins, constraints, views, and indexes in SQL.

• Types of joins in SQL: Inner Join, Left Join, Right Join, Full Join, Cross Join.

• Types of constraints in SQL: Primary Key, Foreign Key, Unique, Not Null, Check.

• Views in SQL are virtual tables that display data from one or more tables. Types include Simple Views, Complex Views, Materialized Views.

• Indexes in SQL are used to quickly retrieve data from a table. Types include Clustered Index, Non-Clustered Index, Unique Index, ...read more

Explanation of inner join, left join, right join, and cross join with given tables a and b.

• Inner join: Returns only the rows where there is a match in both tables based on the specified condition.

• Left join: Returns all rows from the left table and the matched rows from the right table. If there is no match, NULL values are returned.

• Right join: Returns all rows from the right table and the matched rows from the left table. If there is no match, NULL values are returned.

• Cross j...read more

Create a table with team names where each team plays with each other once.

• Create a table teams with column teamname

• Insert team names into the table

• Use a combination of team names to represent matches

To find department wise highest salary and then 5 highest salaries, use SQL queries with GROUP BY and ORDER BY clauses.

• Use SQL query with GROUP BY clause to get department wise highest salary

• Use ORDER BY clause to get 5 highest salaries overall

Delete removes rows one by one and can be rolled back, while truncate removes all rows at once and cannot be rolled back.

• Delete is a DML command, while truncate is a DDL command.

• Delete operation can be rolled back using ROLLBACK, while truncate operation cannot be rolled back.

• Delete operation fires delete triggers on each row, while truncate does not fire any triggers.

• Delete operation is slower as it generates a lot of redo and undo logs, while truncate is faster as it does n...read more

Indexes are data structures that improve the speed of data retrieval operations in a database. There are different types of indexes.

• Indexes are used to quickly locate data without having to search every row in a database table.

• Types of indexes include clustered indexes, non-clustered indexes, unique indexes, and composite indexes.

• Clustered indexes physically reorder the data in the table based on the index key.

• Non-clustered indexes store a separate copy of the indexed columns...read more

There are two types of triggers in SQL: Row-level triggers and Statement-level triggers.

• Row-level triggers are fired for each row affected by the triggering statement.

• Statement-level triggers are fired once for each triggering statement, regardless of the number of rows affected.

• Examples: BEFORE INSERT trigger (row-level), AFTER UPDATE trigger (statement-level)

Functions return a value, while procedures do not.

• Functions must return a value, while procedures do not necessarily return a value.

• Functions can be called in SQL statements, while procedures cannot be called in SQL statements directly.

• Functions can be used in expressions, while procedures cannot be used in expressions.

• Functions are used to compute and return a value, while procedures are used to perform an action.

• Example: Function to calculate the square of a number and retu...read more

A table is a collection of related data stored in rows and columns, while a field is a single piece of data within a table.

• A table is like a spreadsheet with rows and columns, where each row represents a record and each column represents a field

• A field is a specific piece of data within a table, such as a name, age, or address

• Tables and fields are used in databases to organize and store information efficiently

A subset of SQL refers to a smaller set of data or records that meet specific criteria within a larger dataset.

• A subset can be created using the WHERE clause in SQL to filter data based on certain conditions.

• Subsets can also be generated using the SELECT statement to retrieve specific columns from a table.

• Examples of subsets include selecting all customers from a specific city or employees with a certain job title.

Types of joins in SQL are Inner Join, Left Join, Right Join, and Full Join.

• Inner Join: Returns rows when there is a match in both tables.

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

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

• Full Join: Returns rows when there is a match in either table.

SQL joins are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• INNER JOIN returns rows when there is at least one match in both tables

• LEFT JOIN returns all rows from the left table and the matched rows from the right table

• RIGHT JOIN returns all rows from the right table and the matched ro...read more