This file is dedicated to the case statement only

case_in_sql.md

There are 2 types of CASE:

1. General CASE
2. CASE expression

General Syntax

-- General Syntax
CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ELSE result3 AS abc
END

-- Example
SELECT col_1, col_2,
CASE 
    WHEN col_2 = 33 THEN 'Yes!'
    ELSE 'No!'
END
FROM table;

Returns:

col_1	col_2	case
12	33	Yes!
22	211	No!
32	33	Yes!

Expression Syntax

-- General Syntax
CASE column
    WHEN value1 THEN result1
    WHEN value2 THEN result2
    ELSE result3 AS abc
END

-- Example
SELECT col_1, col_2,
CASE col_2
    WHEN 33 THEN 'Yes!'
    ELSE 'No!'
END
FROM table;

Returns:

col_1	col_2	case
12	33	Yes!
22	211	No!
32	33	Yes!

So the difference

General Case	Expression Case
So much flexible allows any condition	Only allows the "equals to" condition
Need to write condition again and again for each case	No repeated condition writing saves time