Write SQL query to solve given problem: Please indicate store id in the state of California that have been applied 20% discount in store.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T FROM ( SELECT DISTINCT CASE  WHEN T2.State = 'California' AND T1.`Sales Channel` = 'In-Store' AND T1.`Discount Applied` = 0.2 THEN T2.StoreID END AS T FROM `Sales Orders` T1 INNER JOIN `Store Locations` T2 ON T2.StoreID = T1._StoreID ) WHERE T IS NOT NULL