db2 compare year and month side by side - sql

Question

I need to compare side by side the companies values by current year vs last year and current month with same month of the previous year.
I use this query to get the values
SELECT STORE, SUM(TOTAL) as VAL, DATE FROM MYTABLE
WHERE DATE=CURRENT_DATE GROUP BY STORE ORDER BY STORE
below the results
STORE | VAL | DATE
1 10 CURRENT_DATE (2018-27-03)
1 20 2018-26-03
1 30 2018-25-03
2 20 CURRENT_DATE (2018-27-03)
2 20 2018-26-02
and i need this
STORE | VALUE CURRENT YEAR | VALUE LAST YEAR
1 60 30 (CALCULATED)
2 40 50 (CALCULATED)
STORE | VALUE CURRENT MONTH | VALUE SAME MONTH OF LAST YEAR
1 60 30 (CALCULATED)
2 20 50 (CALCULATED)
Thank you

Answer 1

You could just join two sub-selects together.
E.g with this DDL and Data
CREATE TABLE MYTABLE (STORE int, VAL int, D DATE);
INSERT INTO MYTABLE VALUES
( 1, 10, '2018-03-27')
,( 1, 20, '2018-03-26')
,( 1, 10, '2018-02-25')
,( 1, 35, '2017-03-25')
,( 2, 20, '2018-03-27')
,( 2, 15, '2017-03-26');
This will get you current month and last month last year values
SELECT C.*, LY.VAL_CURR_MONTH_LY
FROM (
SELECT STORE, SUM(VAL) as VAL_CURR_MONTH
FROM MYTABLE WHERE INT(D)/100=INT(CURRENT_DATE)/100
GROUP BY STORE ) AS C
LEFT JOIN
(SELECT STORE
, SUM(VAL) AS VAL_CURR_MONTH_LY
FROM MYTABLE
WHERE INT(D)/100 = INT(CURRENT_DATE)/100 -100
GROUP BY STORE ) LY
ON
C.STORE = LY.STORE
Then this for years
SELECT C.*, LY.VAL_LY
FROM (
SELECT STORE, SUM(VAL) as VAL_CURR_YEAR
FROM MYTABLE WHERE INT(D)/10000=INT(CURRENT_DATE)/10000
GROUP BY STORE ) AS C
LEFT JOIN
(SELECT STORE
, SUM(VAL) AS VAL_LY
FROM MYTABLE
WHERE INT(D)/10000 = INT(CURRENT_DATE)/10000 -1
GROUP BY STORE ) LY
ON
C.STORE = LY.STORE
P.S. there are many other ways to manipulate dates, but casting to INT is maybe one of the easier ways
Also, here is a more flexible way to get the "Same Month of Last Year" value. A similar method can get "last Year" values.
SELECT T.*
, AVG(VAL) OVER(
PARTITION BY STORE
ORDER BY YEAR_MONTH
RANGE BETWEEN 101 PRECEDING AND 100 PRECEDING
) AS SAME_MONTH_PREV_YEAR
FROM
( SELECT STORE
, INTEGER(D)/100 AS YEAR_MONTH
, SUM(VAL) AS VAL
FROM
MYTABLE T
GROUP BY
STORE
, INTEGER(D)/100
) AS T
;
Gives
STORE YEAR_MONTH VAL SAME_MONTH_PREV_YEAR
----- ---------- --- --------------------
1 201703 35 NULL
1 201802 10 NULL
1 201803 30 35
2 201703 15 NULL
2 201803 20 15

Answer 2

It is better to avoid functions on table columns in where clauses. Check following SQLs which are based on P. Vernon sample table.
Note: These SQLs are for DB2 LUW 11.1
For month:
SELECT STORE,
SUM(CASE WHEN YEAR(D) = year(current date) THEN val
ELSE 0 END) as VAL_CURR_MONTH,
SUM(CASE WHEN YEAR(D) = year(current date) - 1 THEN vaL
ELSE 0 END) as VAL_CURR_MONTH_LY
FROM MYTABLE
WHERE D between first_day(current date) and last_day(current date)
or D between first_day(current date - 1 year) and last_day(current date - 1 year)
GROUP BY STORE
ORDER BY STORE
For year:
SELECT STORE, SUM(CASE WHEN YEAR(D) = year(current date) THEN val
ELSE 0 END) as VAL_CY,
SUM(CASE WHEN YEAR(D) = year(current date) - 1 THEN vaL
ELSE 0 END) as VAL_LY
FROM MYTABLE
WHERE D between first_day(current date - (month(current date) - 1) months)
and last_day(current date + (12 - month(current date)) months)
or D between first_day(current date - (month(current date) - 1) months - 1 year)
and last_day(current date + (12 - month(current date)) months - 1 year)
GROUP BY STORE
ORDER BY STORE