CASE WHEN (IF..ELSE)

CASE WHEN statements provide great flexibility when dealing with buckets of results or when you need to find a way to filter out certain results. Another way to think of it is it's a conditional logic similar to IF-THEN statements in other programming languages.

When using a CASE WHEN statement, it's important to remember you need a condition, what to do when that condition is met, and an END clause. A simple syntax is below:

CASE
  WHEN  condition
    THEN result
  ELSE other_result
END

You can include multiple conditional buckets as needed by adding more WHEN and THEN clauses to your statement, as follows:

SELECT 
CASE
  WHEN  condition
    THEN result
  WHEN  condition_2
    THEN result_2
  WHEN  condition_2     
    THEN result_2
  ELSE other_result
END AS new_column_name

For example, 

SELECT
  CASE
    WHEN country = 'USA'
      THEN 'North America'
    WHEN country = 'Mexico'
      THEN 'North America'
    ELSE country
  END AS 'West Region'

Operators: 

Equals: =
Not Equals: !=

Greater than: >
Less than: <

Greater or equal: >=

Less or equal: <=

Contains: "Like"

Does not contain: "Not Like"