Unions, joins

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UNIONS, JOINS, 
Abdusobur Xalimov

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UNION vs UNION ALL
time_table_asistant
time_table_tutors_hostory
payment
course_payment

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INTERSECT, EXCEPT
time_table_asistant
time_table_tutors_hostory

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LEFT JOIN
●
user balance

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INNER JOIN
payment qilgan userlarni topish
kurs sotib olganlar sonini toping
course_tutor with task_id

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lesson tasks count
unread tasks
unread chats