"IS NOT NULL" not producing the required results in mySQL - mysql

Question

I am trying to build a report based of my table. Here is my table:
Following is the SQL query to get desired results.
SELECT
`user`,
SUM(
CASE
WHEN `event_time` >= '2021-04-01 00:00:00'
AND `event_time` <= '2021-04-16 23:59:59'
AND `sub_status` = 'TB'
THEN pause_sec
END
) AS 'Training Break',
SUM(
CASE
WHEN `event_time` >= '2021-04-01 00:00:00'
AND `event_time` <= '2021-04-16 23:59:59'
AND `sub_status` = 'SB1'
THEN pause_sec
END
) AS 'Short Break 1',
SUM(
CASE
WHEN `event_time` >= '2021-04-01 00:00:00'
AND `event_time` <= '2021-04-16 23:59:59'
AND `sub_status` = 'SB2'
THEN pause_sec
END
) AS 'Short Break 2',
SUM(
CASE
WHEN `event_time` >= '2021-04-01 00:00:00'
AND `event_time` <= '2021-04-16 23:59:59'
AND `sub_status` = 'LB'
THEN pause_sec
END
) AS 'Long Break'
FROM
`vicidial_agent_log`
GROUP BY `user`
I am looking to exclude entries which have all null values and following is my syntax but it is not working and produces the same results.
FROM
`vicidial_agent_log`
WHERE 'Training Break' IS NOT NULL
AND 'Short Break 1' IS NOT NULL
AND 'Short Break 2' IS NOT NULL
AND 'Long Break' IS NOT NULL
GROUP BY `user`
Kindly help here or share a post that can help. I have been trying to find but

Answer 1

Don't use single quotes for column names/aliases, because for example 'Training Break' in an expression like 'Training Break' IS NOT NULL is interpreted as a string literal which of course is not null.
In MySql you can use backticks to surround column names.
Also, the columns Training Break, Short Break 1, Short Break 2 and Long Break are the result of aggregate functions so they can't be used in a WHERE clause. Instead use a HAVING clause.
Finally, since you want the rows where at least 1 of these columns is not null you should use the operator OR instead of AND:
FROM
`vicidial_agent_log`
GROUP BY `user`
HAVING `Training Break` IS NOT NULL
OR `Short Break 1` IS NOT NULL
OR `Short Break 2` IS NOT NULL
OR `Long Break` IS NOT NULL
Or:
FROM
`vicidial_agent_log`
GROUP BY `user`
HAVING COALESCE(`Training Break`, `Short Break 1`, `Short Break 2`, `Long Break`) IS NOT NULL

Answer 2

First, move the common part of the SUM() expressions to the WHERE clause.
Second, fix the date logic so you are not missing a second.
I also strongly, strongly recommend using column names that do not need to be escaped. So:
SELECT user,
SUM(CASE WHEN sub_status` = 'TB' THEN pause_sec END) AS Training_Break,
SUM(CASE WHEN sub_status = 'SB1' THEN pause_sec END) AS Short_Break_1,
SUM(CASE WHEN sub_status = 'SB2' THEN pause_sec END) AS Short_Break_2,
SUM(CASE WHEN sub_status = 'LB' THEN pause_sec END) AS Long_Break
FROM vicidial_agent_log
WHERE event_time >= '2021-04-01' AND
event_time < '2021-04-17'
GROUP BY user;
This will probably eliminate the NULL values and speed up the query. However, if there are still NULL values in an entire row, it is because there are rows that don't have one of these statuses. So, just check for them:
SELECT user,
SUM(CASE WHEN sub_status` = 'TB' THEN pause_sec END) AS Training_Break,
SUM(CASE WHEN sub_status = 'SB1' THEN pause_sec END) AS Short_Break_1,
SUM(CASE WHEN sub_status = 'SB2' THEN pause_sec END) AS Short_Break_2,
SUM(CASE WHEN sub_status = 'LB' THEN pause_sec END) AS Long_Break
FROM vicidial_agent_log
WHERE event_time >= '2021-04-01' AND
event_time < '2021-04-17' AND
sub_status IN ('TB', 'SB1', 'SB2', 'LB')
GROUP BY user;
SQL is very powerful in letting you filter before or after aggregation. However, it is usually much better (from a performance perspective) to filter before aggregating.
I also advise you to use identifiers that do not need to be escaped. And, never use single quotes for anything other than string and date literals.