case expression in sql code example

Example 1: sql case

-- NOTE: this is for SQL-Oracle specifically

/*
NB: Please like Mingles444 post, I derived this from him/her
*/

-- syntax: (Retrieved from grepper:Mingles444)
CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    WHEN conditionN THEN resultN
    ELSE result
END 

-- example:
SELECT 
	CASE
      WHEN (1+6 = 6) THEN 'A'
      WHEN (1+6 = 7) THEN 'B'
      WHEN (1+6 = 8) THEN 'C'
      ELSE 'D'
	END 
FROM DUAL;

-- OUTPUT: B

Example 2: sql case

Change query output depending on conditions.
Example: Returns users and their subscriptions, along with a new column
called activity_levels that makes a judgement based on the number of
subscriptions.
SELECT first_name, surname, subscriptions
CASE WHEN subscriptions > 10 THEN 'Very active'
WHEN Quantity BETWEEN 3 AND 10 THEN 'Active'
ELSE 'Inactive'
END AS activity_levels
FROM users;

Example 3: sql CASE

/*CASE statements are used to create different outputs and is 
  used by SQL as a way to handle if-then logic.*/
  
  SELECT column_name,
    CASE 
      WHEN condition THEN 'Result_1'
      WHEN condition THEN 'Result_2'
      ELSE 'Result_3'
    END
  FROM table_name;

Example 4: case statement in sql

Case Statement basically
Like IF - THEN - ELSE statement.

The CASE statement goes through conditions
and returns a value when the
first condition is met and
once a condition is true,
it will stop reading and return the result.
If no conditions are true,
it returns the value in the ELSE clause.

If there is no ELSE part and
no conditions are true, it returns NULL.

FOR EXAMPLE =

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    WHEN conditionN THEN resultN
    ELSE result
END 

-- example:
SELECT 
	CASE
      WHEN (1+6 = 6) THEN 'A'
      WHEN (1+6 = 7) THEN 'B'
      WHEN (1+6 = 8) THEN 'C'
      ELSE 'D'
	END 
FROM DUAL;

Result would be 'B' since it is the first
correct answer