-- create table
CREATE TABLE TB_INVENTORY(
	DATE_INVENT		DATE,
	PRODUCT			VARCHAR(50),
	QUANTITY		INT
)

-- insert some dummy data into table
INSERT INTO TB_INVENTORY VALUES (CONVERT(DATE,'2021-01-01',23),'ITEM0001',150)
INSERT INTO TB_INVENTORY VALUES (CONVERT(DATE,'2021-01-10',23),'ITEM0001',200)
INSERT INTO TB_INVENTORY VALUES (CONVERT(DATE,'2021-01-15',23),'ITEM0001',300)
INSERT INTO TB_INVENTORY VALUES (CONVERT(DATE,'2021-01-20',23),'ITEM0001',100)
INSERT INTO TB_INVENTORY VALUES (CONVERT(DATE,'2021-01-28',23),'ITEM0001',50)


-- declare table
DECLARE @DATE_INVENT		VARCHAR(1000)
DECLARE @DATE_INVENT_PREV	VARCHAR(1000)
DECLARE @count	INT
DECLARE @LIMIT	INT

-- declare cursor
 DECLARE INVENTORY_DAYLIST_CR CURSOR 
    FOR  
select DISTINCT DATE_INVENT 
  from TB_INVENTORY 
ORDER by DATE_INVENT ASC 

-- open cursor
OPEN INVENTORY_DAYLIST_CR;

-- fetch into previous date
FETCH NEXT FROM INVENTORY_DAYLIST_CR INTO @DATE_INVENT_PREV;

WHILE @@FETCH_STATUS = 0  
    BEGIN
		-- fetch next date into current date
		FETCH NEXT FROM INVENTORY_DAYLIST_CR INTO @DATE_INVENT;

		PRINT 'PREVIOUS DATE: '+@DATE_INVENT_PREV+' DATE: '+@DATE_INVENT;
		-- if difference between previous and current date is bigger than 1
		IF DATEDIFF(DAY,@DATE_INVENT_PREV,@DATE_INVENT) > 1
		BEGIN
			-- initialize counter with 1
			SET @count = 1
			-- get the difference between two dates
			SET @LIMIT = DATEDIFF(DAY,@DATE_INVENT_PREV,@DATE_INVENT)
			-- while counter is smaller than limit
			WHILE @count< @LIMIT
			BEGIN
				-- insert the value for previous date into previous date + count
			   	INSERT INTO TB_INVENTORY (DATE_INVENT,   PRODUCT,   QUANTITY)
				 SELECT DATEADD(DAY,@COUNT,@DATE_INVENT_PREV), PRODUCT,   QUANTITY
				   FROM TB_INVENTORY
				  WHERE DATE_INVENT = @DATE_INVENT_PREV
				-- increase the counter by 1
			   SET @count = @count + 1;
			END;
		END
		-- store value of current date into previous date
		SET @DATE_INVENT_PREV = @DATE_INVENT
		
    END;

-- close cursor
CLOSE INVENTORY_DAYLIST_CR;
-- flush cursor out the memory
DEALLOCATE INVENTORY_DAYLIST_CR;


SELECT *
  FROM TB_INVENTORY
  ORDER BY DATE_INVENT ASC