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Literal values

Learn to use constants and calculations inside SELECT.

Literal values

You can use constant values inside SELECT. It can produce output without even querying a table.

SELECT 'Hello' AS greeting;
SELECT 1 + 1 AS total;

The first query prints Hello on each row. The second returns 2. Text goes in single quotes; numbers do not. You can also compute: price * 2.

The expression 'Merhaba' AS selam is evaluated and returned.

Literal values — details

You can do arithmetic inside SELECT. The +, -, *, / operators work.

SELECT name, price * 1.18 AS with_tax
FROM products;

This multiplies each price by 1.18. A single row can show both a raw column and a computed value.

name, price * 1.18 AS kdvli is selected from products.

Practice Literal values

Select the price column from products, multiply by 2 and alias it as double_price.

Starter code

query.sql
-- multiply price by 2 and alias
SELECT
FROM products

Sample solution

query.sql
SELECT price * 2 AS cift_fiyat
FROM products

Expected output

cift_fiyat
10
24

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Number calculation

Question 
SELECT 2 +____ AS toplam;
Answer 
SELECT 2 + 3 AS toplam;

Explanation: SELECT can calculate without a table; 2 + 3 gives 5, shown under the name toplam.

2 Literal values: match the terms

Term Meaning
'Hello' text
42 integer
3.14 decimal
TRUE boolean

3 How is a text literal written?

  • In single quotes Correct answer
  • In double quotes
  • Without quotes
  • In square brackets

Explanation: Text goes in single quotes.

All lessons in Beginner

1 SELECT basics

  1. What is SELECT?
  2. Selecting all columns
  3. Selecting specific columns
  4. Column aliases with AS
  5. Literal values
  6. Summary - SELECT basics

2 WHERE filtering

  1. What is WHERE?
  2. Comparison operators
  3. AND and OR
  4. IN and BETWEEN
  5. Pattern matching with LIKE
  6. Summary - WHERE filtering

3 Ordering and limit

  1. ORDER BY
  2. ASC and DESC
  3. Multi-column ordering
  4. LIMIT
  5. OFFSET
  6. Summary - Ordering and limit

4 Project: CRUD app

  1. Project design
  2. Reading data
  3. Inserting data
  4. Updating data
  5. Deleting data

5 Data types

  1. Integer types
  2. Decimal types
  3. CHAR and VARCHAR
  4. DATE and TIME
  5. BOOLEAN
  6. Summary - Data types

6 Operators

  1. Arithmetic operators
  2. Comparison operators
  3. Logical operators
  4. IS NULL
  5. String concatenation
  6. Summary - Operators

7 String functions

  1. UPPER and LOWER
  2. LENGTH
  3. SUBSTRING
  4. TRIM
  5. CONCAT
  6. Summary - String functions

8 Project: Shopping cart

  1. Cart design
  2. Listing products
  3. Adding to cart
  4. Calculating total
  5. Removing from cart

9 Number functions

  1. ROUND
  2. CEIL and FLOOR
  3. ABS
  4. POWER and SQRT
  5. MOD
  6. Summary - Number functions

10 Date functions

  1. CURRENT_DATE and NOW
  2. EXTRACT
  3. Date arithmetic
  4. DATEDIFF
  5. Date formatting
  6. Summary - Date functions

11 NULL handling

  1. What is NULL?
  2. IS NULL
  3. COALESCE
  4. NULLIF
  5. Three-valued logic
  6. Summary - NULL handling

12 DISTINCT

  1. What is DISTINCT?
  2. DISTINCT on one column
  3. Multi-column DISTINCT
  4. DISTINCT with aggregates
  5. DISTINCT vs GROUP BY
  6. Summary - DISTINCT

13 INSERT

  1. INSERT basics
  2. Inserting into specific columns
  3. Multiple rows
  4. INSERT with SELECT
  5. DEFAULT values
  6. Summary - INSERT

14 UPDATE

  1. UPDATE basics
  2. Conditional UPDATE
  3. Multi-column UPDATE
  4. Calculated updates
  5. UPDATE pitfalls
  6. Summary - UPDATE

15 DELETE

  1. DELETE basics
  2. Conditional DELETE
  3. DELETE vs TRUNCATE
  4. Emptying a table
  5. Safe deletion
  6. Summary - DELETE

16 CREATE TABLE

  1. CREATE TABLE basics
  2. Column definitions
  3. NOT NULL
  4. DEFAULT
  5. PRIMARY KEY
  6. Summary - CREATE TABLE

17 Constraints

  1. UNIQUE constraint
  2. CHECK constraint
  3. FOREIGN KEY
  4. CASCADE
  5. Constraint management
  6. Summary - Constraints

18 Simple JOIN

  1. What is JOIN?
  2. INNER JOIN
  3. The ON clause
  4. Table aliases
  5. Multi-table JOIN
  6. Summary - Simple JOIN

19 Project: Inventory system

  1. Inventory design
  2. Product table
  3. Stock movements
  4. Stock report
  5. Low stock alert

20 Beginner final

  1. Customer query
  2. Order report
  3. Data update
  4. Table redesign