Get percentage of increase/decrease from two results base on their WHERE clause - oracle

Question

I don't know if my Title is understandable but what I am really trying to achieve is get the percentage increase/decrease of Result 2 from Result 1.
I have a SALES table with these sample data:
DATE. AMOUNT
01-JAN-20. 500
02-JAN-20. 400
...
15-MAR-20. 1000
Assume that the table is filled with daily sales.
Now, with the Dashboard app I'm trying to make in APEX, I want to display the TOTAL AMOUNT base from the DATE the user will choose on a SELECT list (Today, This Week, This Month).
So basically, these would be the queries:
SELECT SUM(AMOUNT) TOTAL_SALES FROM TB_SALES WHERE DATE = TRUNC(SYSDATE); - Today
SELECT SUM(AMOUNT) TOTAL_SALES FROM TB_SALES WHERE DATE BETWEEN TRUNC(SYSDATE-7,'SUNDAY') AND TRUNC(SYSDATE); - This Week
SELECT SUM(AMOUNT) TOTAL_SALES FROM TB_SALES WHERE DATE BETWEEN TRUNC(SYSDATE, 'MM' AND TRUNC(SYSDATE); - This Month
To get the percentage of increase or decrease, I now then need to get the result of same queries but different DATE from the WHERE clause.
So with Yesterday, I should query
TRUNC(SYSDATE -1);
And so on. Actually I still don't know how to get the This week part.
With the two results, I can now calculate the percentage.
What I can't figure out is how can I query this two WHERE clause of two DATEs. My current temporary solution is to query the second query and just use JavaScript to update my Card.
I found something about LAG functions but cannot find any sample which uses WHERE clause to compare the results.
EDIT:
To be more clear, this is what I want to compare and get the percentage.
Today VS Yesterday
This week VS Last week
This month VS Last month

Answer 1

You can use conditional aggregation to find the totals:
SELECT SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE )
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_today,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE ) - INTERVAL '1' DAY
AND "DATE" < TRUNC( SYSDATE )
THEN AMOUNT
ELSE NULL
END
) AS total_yesterday,
SUM(
CASE
WHEN "DATE" >= NEXT_DAY( TRUNC( SYSDATE ) - INTERVAL '7' DAY, 'SUNDAY' )
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_week,
SUM(
CASE
WHEN "DATE" >= NEXT_DAY( TRUNC( SYSDATE ) - INTERVAL '14' DAY, 'SUNDAY' )
AND "DATE" < NEXT_DAY( TRUNC( SYSDATE ) - INTERVAL '7' DAY, 'SUNDAY' )
THEN AMOUNT
ELSE NULL
END
) AS total_last_week,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE, 'IW' ),
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_iso_week,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE, 'IW' ) - INTERVAL '7' DAY,
AND "DATE" < TRUNC( SYSDATE, 'IW' )
THEN AMOUNT
ELSE NULL
END
) AS total_last_iso_week,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE ) - INTERVAL '6' DAY,
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_7_days,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE ) - INTERVAL '13' DAY,
AND "DATE" < TRUNC( SYSDATE ) - INTERVAL '6' DAY
THEN AMOUNT
ELSE NULL
END
) AS total_last_7_days,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE, 'MM' )
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_month
SUM(
CASE
WHEN "DATE" >= ADD_MONTHS( TRUNC( SYSDATE, 'MM' ), -1 )
AND "DATE" < TRUNC( SYSDATE, 'MM' )
THEN AMOUNT
ELSE NULL
END
) AS total_this_month
FROM tb_sales
WHERE "DATE" >= ADD_MONTHS( TRUNC( SYSDATE, 'MM' ), -1 )
AND "DATE" <= SYSDATE;
This will find the totals for:
Today and yesterday;
This week and last week (starting from midnight Sunday until before the midnight of the next Sunday or until this instant, whichever is earlier);
This ISO 8601 week and last ISO 8601 week (starting midnight Monday);
The last 7 days (today and the previous 6 days) and 7 days before that; and
This month and last month (from midnight of the first day of the month until this instant).
If you want the percentage increases compared to a previous period then:
SELECT 100 * ( total_this_today / total_yesterday - 1 ) AS percent_increase_this_today,
100 * ( total_this_week / total_last_week - 1 ) AS percent_increase_this_week,
100 * ( total_this_iso_week / total_last_iso_week - 1 ) AS percent_increase_this_iso_week,
100 * ( total_this_7_days / total_last_7_days - 1 ) AS percent_increase_this_7_days,
100 * ( total_this_month / total_last_month - 1 ) AS percent_increase_this_month
FROM (
SELECT SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE )
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_today,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE ) - INTERVAL '1' DAY
AND "DATE" < TRUNC( SYSDATE )
THEN AMOUNT
ELSE NULL
END
) AS total_yesterday,
SUM(
CASE
WHEN "DATE" >= NEXT_DAY( TRUNC( SYSDATE ) - INTERVAL '7' DAY, 'SUNDAY' )
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_week,
SUM(
CASE
WHEN "DATE" >= NEXT_DAY( TRUNC( SYSDATE ) - INTERVAL '14' DAY, 'SUNDAY' )
AND "DATE" < NEXT_DAY( TRUNC( SYSDATE ) - INTERVAL '7' DAY, 'SUNDAY' )
THEN AMOUNT
ELSE NULL
END
) AS total_last_week,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE, 'IW' ),
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_iso_week,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE, 'IW' ) - INTERVAL '7' DAY,
AND "DATE" < TRUNC( SYSDATE, 'IW' )
THEN AMOUNT
ELSE NULL
END
) AS total_last_iso_week,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE ) - INTERVAL '6' DAY,
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_7_days,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE ) - INTERVAL '13' DAY,
AND "DATE" < TRUNC( SYSDATE ) - INTERVAL '6' DAY
THEN AMOUNT
ELSE NULL
END
) AS total_last_7_days,
SUM(
CASE
WHEN "DATE" >= TRUNC( SYSDATE, 'MM' )
AND "DATE" <= SYSDATE
THEN AMOUNT
ELSE NULL
END
) AS total_this_month
SUM(
CASE
WHEN "DATE" >= ADD_MONTHS( TRUNC( SYSDATE, 'MM' ), -1 )
AND "DATE" < TRUNC( SYSDATE, 'MM' )
THEN AMOUNT
ELSE NULL
END
) AS total_this_month
FROM tb_sales
WHERE "DATE" >= ADD_MONTHS( TRUNC( SYSDATE, 'MM' ), -1 )
AND "DATE" <= SYSDATE
)