SQL Notes

What is the standard language for storing, manipulating, and retrieving data in databases?

SQL (Structured Query Language)

What does RDBMS stand for?

Relational Database Management System.

Are SQL keywords case-sensitive?

No!

What does the SELECT statement do?

Extracts Data From Database.

What is the purpose of the DISTINCT keyword in SQL?

It is used to return only distinct values.

What SQL syntax would you use to count the number of different countries in a table?

SELECT COUNT(DISTINCT column_name) FROM table_name;

What is the function of the SELECT INTO statement?

It copies data from one table into a new table.

What does the INSERT INTO SELECT statement do?

It copies data from one table and inserts it into another table.

What does the CASE expression do in SQL?

It goes through conditions and returns a value when the first condition is met.

What does the WHERE clause do in SQL?

It is used to filter records.

What does the GROUP BY statement do in SQL?

It groups rows that have the same values into summary rows.

What type of JOIN returns all records from the left table and the matched records from the right table?

LEFT JOIN.

What is the purpose of the UNION operator in SQL?

It combines the result set of two or more SELECT statements.

What does the NOT NULL constraint do?

Ensures that a column cannot have a NULL value.

What is the use of the SUM() function in SQL?

It returns the total sum of a numerical column.

What does the IS NULL operator do?

Used to test for empty (NULL) values.

What is the purpose of the AUTO_INCREMENT feature?

It generates a unique number automatically when a new record is inserted into a table.

What do Microsoft SQL Server and MS Access use for auto-increment features?

IDENTITY keyword for SQL Server and AUTOINCREMENT keyword for MS Access.

What is a stored procedure in SQL?

A prepared SQL code that you can save for reuse.