t sql case

1-- NOTE: this is for SQL-Oracle specifically
2
3/*
4NB: Please like Mingles444 post, I derived this from him/her
5*/
6
7-- syntax: (Retrieved from grepper:Mingles444)
8CASE
9    WHEN condition1 THEN result1
10    WHEN condition2 THEN result2
11    WHEN conditionN THEN resultN
12    ELSE result
13END 
14
15-- example:
16SELECT 
17	CASE
18      WHEN (1+6 = 6) THEN 'A'
19      WHEN (1+6 = 7) THEN 'B'
20      WHEN (1+6 = 8) THEN 'C'
21      ELSE 'D'
22	END 
23FROM DUAL;
24
25-- OUTPUT: B
26

1-- Syntax for SQL Server, Azure SQL Database and Azure Synapse Analytics
2  
3--Simple CASE expression:   
4CASE input_expression   
5     WHEN when_expression THEN result_expression [ ...n ]   
6     [ ELSE else_result_expression ]   
7END   
8
9--Searched CASE expression:  
10CASE  
11     WHEN Boolean_expression THEN result_expression [ ...n ]   
12     [ ELSE else_result_expression ]   
13END  
14

1/*CASE statements are used to create different outputs and is 
2  used by SQL as a way to handle if-then logic.*/
3  
4  SELECT column_name,
5    CASE 
6      WHEN condition THEN 'Result_1'
7      WHEN condition THEN 'Result_2'
8      ELSE 'Result_3'
9    END
10  FROM table_name;

1Change query output depending on conditions.
2Example: Returns users and their subscriptions, along with a new column
3called activity_levels that makes a judgement based on the number of
4subscriptions.
5SELECT first_name, surname, subscriptions
6CASE WHEN subscriptions > 10 THEN 'Very active'
7WHEN Quantity BETWEEN 3 AND 10 THEN 'Active'
8ELSE 'Inactive'
9END AS activity_levels
10FROM users;