How to get columns as zero when there is no data for a specific date in PostgresSql with Springboot - postgresql

Question

I'm using PostgreSql. I have a query that gives values for a specific date range. How can i get the columns as zero when there is no data for a specific date.
Example: the date range is '2018-06-10' to '2018-06-16', and there is no data for the dates 2018-06-15 and 2018-06-16. My existing query returns data for 10th,11th,12th,13th and 14th but not 15th and 16th. How can i get 15th and 16th dates with columns as zeroes.
here's my query:
SELECT 40 AS clientId,
0 AS accountId,
0 AS searchEngineId,
'present' AS dateType,
SUM(em.clicks) AS clicks,
To_date(em.DATE, 'YYYY-MM-dd') AS date
FROM emailreportstats em
WHERE em.clientid = 40
AND em.accountid IN ( 13, 14 )
AND em.DATE BETWEEN '2018-06-10' AND '2018-06-16'
GROUP BY em.DATE,
em.datetype;
Code to execute query:
Query query = em.createQuery(pSqlQuery, EmailReportStats.class);
emailReportStatses = query.getResultList();

Answer 1

You need a calendar table. You can generate one on the fly (available only for this query) using generate_series function. Then you would outer join your emailreportstats to that table, so that you would have all dates covered even if they are not present in your email table.
I've added coalesce() wrap to your calculated clicks column and also swapped the input for date column.
This is as far as I can go having no table structures and sample data to test it.
SELECT
40 AS clientId,
0 AS accountId,
0 AS searchEngineId,
'present' AS dateType,
COALESCE(SUM(em.clicks),0) AS clicks,
calendar.dt AS date
FROM (
SELECT dt::date as dt
FROM generate_series('2018-06-10', '2018-06-16', '1 day') g(dt) -- input your dates here
) calendar
LEFT JOIN emailreportstats em ON
calendar.dt = em.date::date
WHERE
em.clientid = 40
AND em.accountid IN ( 13, 14 )
GROUP BY
calendar.dt,
em.datetype
;