Seleccionar substring entre dos strings conocidos respetando mayúsculas y minúsculas, Sql Server

Language: Layout:

--Sql Server 2014 Express Edition

CREATE TABLE m
    ([DESCRIPTION] varchar(200))
;
    
INSERT INTO m
    ([DESCRIPTION])
VALUES
    ('ID=123444,CATEGORY=abc,OTRO=####'),
    ('ID=123444,CATEGORY=abc,OTRO=####,MAS=GHIJK'),
    ('ID=123444,category=abc,OTRO=####'),
    ('ID=123444,CATegoRY=abc,OTRO=####'),
    ('ID=123444,CATEGORY=ABC'),
    ('ID=123444,Category=ABC'),
    ('ID=123444,CATEGORY='),
    ('CATEGORY=abc,OTRO=####'),
    ('CATEGORY=abc'),
    ('ID=123444,OTRO=####'),
    ('ABCDEF')
;

SELECT m.DESCRIPTION,
       CASE WHEN CHARINDEX('CATEGORY=',m.DESCRIPTION COLLATE Latin1_General_CS_AS) > 0
                 THEN SUBSTRING(m.DESCRIPTION,
                                CHARINDEX('CATEGORY=',m.DESCRIPTION COLLATE Latin1_General_CS_AS) + LEN('CATEGORY='),
                                CHARINDEX(',',m.DESCRIPTION+',',CHARINDEX('CATEGORY=',m.DESCRIPTION COLLATE Latin1_General_CS_AS)+1)
                                   - CHARINDEX('CATEGORY=',m.DESCRIPTION COLLATE Latin1_General_CS_AS) 
                                   - LEN('CATEGORY=')
                               )
            ELSE ''
       END AS Resultado
FROM m;

View schema
Execution time: 0,02 sec, rows selected: 11, rows affected: 11, absolute service time: 0,19 sec

Seleccionar substring entre dos strings conocidos respetando mayúscula...