SQL Concepts

What is a JOIN in SQL?

• A JOIN in SQL is used to combine rows from two or more tables based on a related column between them.

• A JOIN in SQL is used to create new tables

• A JOIN in SQL is used to delete rows from a table

• A JOIN in SQL is used to update rows in a table

Explain the difference between INNER JOIN and OUTER JOIN.

• INNER JOIN returns all rows, OUTER JOIN only returns matching rows

• INNER JOIN combines all rows, OUTER JOIN only returns matching rows

• INNER JOIN returns all rows, OUTER JOIN combines all rows

• INNER JOIN compares and returns matching rows, OUTER JOIN returns all rows with NULLs for missing matches.

How do you perform a self-join in SQL?

• SELECT a.column1, b.column2 FROM table_name a INNER JOIN table_name b ON a.related_column = b.related_column

• SELECT a.column1, b.column2 FROM table_name a JOIN table_name b ON a.related_column = b.related_column

• SELECT a.column1, b.column2 FROM table_name a RIGHT JOIN table_name b ON a.related_column = b.related_column

• SELECT a.column1, b.column2 FROM table_name a LEFT JOIN table_name b ON a.related_column = b.related_column

What is a subquery in SQL?

• A subquery in SQL is a query nested within another query.

• A subquery in SQL is a query that can only be used in SELECT statements

• A subquery in SQL is a query that is always executed first

• A subquery in SQL is a query that returns multiple columns

Give an example of using the WHERE clause in a SQL query.

• SELECT * FROM table_name WHERE column_name = specific_value;

• SELECT * FROM table_name WHERE column_name = specific_value;

• SELECT * FROM table_name WHERE column_name != 'specific_value';

• SELECT * FROM table_name WHERE column_name = 'specific_value';

What is the purpose of the GROUP BY clause in SQL?

• To group rows with the same values together for aggregate function calculations.

• To update values in a specific column

• To filter rows based on a specific condition

• To sort rows in ascending order based on a specific column

Explain the difference between the HAVING clause and the WHERE clause.

• The HAVING clause filters rows before grouping, and the WHERE clause filters rows after grouping.

• The HAVING clause is used with SELECT statements, and the WHERE clause is used with UPDATE statements.

• The HAVING clause can be used with aggregate functions, and the WHERE clause cannot.

• The WHERE clause filters rows before grouping, and the HAVING clause filters rows after grouping.

What is the ORDER BY clause used for in SQL?

• Joining tables in a query

• Filtering rows in a query

• Sorting the result set of a query

• Grouping rows in a query

How can you limit the number of rows returned in a SQL query?

• Use the 'LIMIT' clause in the SQL query.

• Manually filter the results after fetching all rows.

• Set a limit on the database server configuration.

• Use the 'MAX_ROWS' clause in the SQL query.

What is the difference between the LIKE and the IN operators in SQL?

• The LIKE operator is for pattern matching, while the IN operator is for specifying multiple values.

• The LIKE operator is for range matching, while the IN operator is for specifying single values.

• The LIKE operator is for exact matching, while the IN operator is for pattern matching.

• The LIKE operator is for specifying multiple values, while the IN operator is for pattern matching.