Você pode usar a instrução CASE ou DECODE dentro da função COUNT.
SELECT item_category,
COUNT (*) total,
COUNT (DECODE (item_status, 'serviceable', 1)) AS serviceable,
COUNT (DECODE (item_status, 'under_repair', 1)) AS under_repair,
COUNT (DECODE (item_status, 'condemned', 1)) AS condemned
FROM mytable
GROUP BY item_category;
Saída:
ITEM_CATEGORY TOTAL SERVICEABLE UNDER_REPAIR CONDEMNED
----------------------------------------------------------------
chair 5 1 2 2
table 5 3 1 1
