Unit 3 Database - Implementation - SQL SELECT

Question 1

What is SQL used for?

Answer 1

SQL is used to add, display, change, or delete data from a database.

Question 2

What does a SQL statement consist of?

Answer 2

A SQL statement consists of instructions to interact with a database.

Question 3

What does the SELECT statement do?

Answer 3

The SELECT statement retrieves and displays data from a table based on specified conditions.

Question 4

What is the syntax for the SELECT clause?

Answer 4

SELECT * | column1, column2, … FROM table1, table2, …

Question 5

What does the wildcard ‘’ mean in SQL?

Answer 5

The wildcard ‘’ means selecting all columns from a table.

Question 6

How do you retrieve specific columns from a table?

Answer 6

Specify the column names after the SELECT keyword, e.g., SELECT userid, accountname FROM user;

Question 7

What does ORDER BY do in SQL?

Answer 7

ORDER BY sorts the query results in ascending (ASC) or descending (DESC) order.

Question 8

How do you retrieve all data from a single table?

Answer 8

Use SELECT * FROM table_name;

Question 9

How do you retrieve a single column from a table?

Answer 9

Use SELECT column_name FROM table_name;

Question 10

How do you retrieve two columns from a table?

Answer 10

Use SELECT column1, column2 FROM table_name;

Question 11

What is an equi-join in SQL?

Answer 11

An equi-join is a join that matches rows based on equality between a primary key and a foreign key.

Question 12

How do you perform an equi-join between two tables?

Answer 12

Use SELECT * FROM table1, table2 WHERE table1.primary_key = table2.foreign_key;

Question 13

How do you retrieve data from two tables with a specific condition?

Answer 13

Use SELECT * FROM table1, table2 WHERE table1.primary_key = table2.foreign_key AND condition;

Question 14

How do you use the ‘AND’ operator in SQL?

Answer 14

Use AND to ensure multiple conditions are met, e.g., WHERE column1 = value1 AND column2 = value2;

Question 15

How do you use the ‘OR’ operator in SQL?

Answer 15

Use OR to allow either condition to be met, e.g., WHERE column1 = value1 OR column2 = value2;

Question 16

How do you use both ‘AND’ and ‘OR’ in SQL?

Answer 16

Use parentheses to group OR conditions with AND, e.g., WHERE column1 = value1 AND (column2 = value2 OR column3 = value3);

Question 17

How do you sort query results in descending order?

Answer 17

Use ORDER BY column_name DESC;

Question 18

How do you sort query results in ascending order?

Answer 18

Use ORDER BY column_name ASC;

Question 19

How do you retrieve specific rows based on multiple conditions?

Answer 19

Use WHERE with multiple conditions joined by AND or OR, e.g., WHERE column = value1 OR column = value2;

Question 20

How do you retrieve specific columns from two tables?

Answer 20

Use SELECT table1.column1, table2.column2 FROM table1, table2 WHERE table1.primary_key = table2.foreign_key;

Question 21

How do you order query results by multiple columns?

Answer 21

Use ORDER BY column1 DESC, column2 ASC;

Question 22

How do you retrieve data for a specific client?

Answer 22

Use WHERE clientid = value;

Question 23

How do you order results by multiple conditions in SQL?

Answer 23

Use ORDER BY column1 sorting_order, column2 sorting_order;