MySQL 8.0

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CREATE TABLE slm (

`id` INTEGER,

`grade_level` VARCHAR(7),

`period` VARCHAR(18)

);

INSERT INTO slm

(`id`, `grade_level`, `period`)

VALUES

('1', 'Grade 1', '1st Grading Period'),

('2', 'Grade 2', '2nd Grading Period');

CREATE TABLE slm_activities (

`id` INTEGER,

`slmid` INTEGER,

`activity` INTEGER,

`count` INTEGER

);

INSERT INTO slm_activities

(`id`, `slmid`, `activity`, `count`)

VALUES

('1', '1', '77', '5'),

('2', '2', '72', '6');

CREATE TABLE periods (

`id` INTEGER,

`period` VARCHAR(18)

);

INSERT INTO periods

(`id`, `period`)

VALUES

('1', '1st Grading Period'),

('2', '2nd Grading Period'),

('3', '3rd Grading Period'),

id	grade_level	period
1	Grade 1	1st Grading Period
2	Grade 2	2nd Grading Period

id	slmid	activity	count
1	1	77	5
2	2	72	6

SELECT SUM(IFNULL(count,0)) AS activitycount, activities.activity, periods.period

FROM activities

CROSS JOIN periods

LEFT JOIN slm ON periods.period = slm.period

LEFT JOIN slm_activities ON activities.id = slm_activities.activity

AND slm.id=slm_activities.slmid

GROUP BY activities.activity, periods.period

ORDER BY activities.activity, periods.period;