Categorize age ranges and display in one column

I want to see the data as follows

Member   Age  Category
Test1    25    Under 30
Test2    55    51-60
Test3    67    Above 60

I have used the below query (from an answer to my previous question) to calculate the age from DOB and current date and then categorize each age under one name.

This query is creating separate columns, instead I want to see all the categories under one column so that I can group this category column

WITH AgeData as
(
SELECT
    Username,
    Birthdate,
    DATEDIFF(YEAR, birthdate, GETDATE()) AS AGE
FROM @Table)
SELECT
    Username,
    Birthdate,
    Age,
    CASE
        WHEN AGE  50 THEN 1
        ELSE 0
    END AS 'Over 50'
FROM AgeData

Instead of using multiple CASE expressions, one for each group, just combine them into a single expression. Then, in the THEN clause you can use something more descriptive to group on later. In the example below I used the column aliases you provided.

WITH AgeData as
(
  SELECT [Username],
         [Birthdate],
         DATEDIFF(YEAR, [Birthdate], GETDATE()) AS [AGE]
  FROM @table
),
GroupAge AS
(
  SELECT [Username],
         [Birthdate],
         [Age],
         CASE
             WHEN AGE  50 THEN 'Over 50'
             ELSE 'Invalid Birthdate'
         END AS [Age Groups]
  FROM AgeData
)
SELECT COUNT(*) AS [AgeGrpCount],
       [Age Groups]
FROM GroupAge
GROUP BY [Age Groups];

StackExchange Database Administrators Q#115780, answer score: 9