Mastering SQL Concepts

What is the purpose of the SELECT statement in SQL?

• To retrieve data from a database.

• To delete data from a database.

• To create new tables in a database.

• To update existing records in a database.

How do you retrieve all columns from a table named 'employees'?

• GET * FROM employees;

• SELECT ALL FROM employees;

• FETCH * FROM employees;

• SELECT * FROM employees;

What SQL command is used to insert new records into a table?

• INSERT INTO

• UPDATE

• SELECT * FROM

• DELETE FROM

Explain the difference between INNER JOIN and LEFT JOIN.

• INNER JOIN returns matched rows only; LEFT JOIN returns all left table rows and matched right table rows.

• INNER JOIN returns all rows from both tables; LEFT JOIN returns only unmatched rows.

• INNER JOIN returns all rows from the right table; LEFT JOIN returns only matched rows from the left table.

• INNER JOIN includes all rows from the left table; LEFT JOIN excludes unmatched rows from the right table.

How can you update existing records in a table using SQL?

• DELETE FROM table_name WHERE condition;

• INSERT INTO table_name VALUES (value1, value2);

• SELECT * FROM table_name WHERE condition;

• UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;

What is the function of the WHERE clause in a SQL query?

• The WHERE clause defines the columns to be selected in the query.

• The WHERE clause filters records based on specified conditions.

• The WHERE clause groups records by specified fields.

• The WHERE clause sorts records in ascending order.

How do you delete records from a table based on a condition?

• DELETE table_name IF condition;

• DELETE FROM table_name WHERE condition;

• REMOVE FROM table_name WHERE condition;

• DROP table_name WHERE condition;

What SQL command is used to create a new table?

• INSERT TABLE

• CREATE TABLE

• ADD TABLE

• MODIFY TABLE

Describe the role of the GROUP BY clause in SQL queries.

• The GROUP BY clause combines all rows into a single row without aggregation.

• The GROUP BY clause groups rows sharing a property so that aggregate functions can be applied to each group.

• The GROUP BY clause is used to filter rows based on a condition.

• The GROUP BY clause sorts the results of a query alphabetically.

What is the purpose of the ORDER BY clause in a SQL statement?

• To group the result set of a query.

• To filter the result set of a query.

• To limit the number of rows returned by a query.

• To sort the result set of a query.