Ashok:
I'm sorry you are having problems. This does not seem to be a Moodle issue specifically, but rather a corrupt database. This might happen if you have a hard drive issue, lose power during a write operation in certain cases, etc. Some sql management programs, like SQLyog have additional tools that you may want to try for repair. You don't say if you can execute a sql statement on the assignment table *after* you did the repair; that would be important. Also, make sure that your table "course_modules" exists as that ties assignments to course topics, etc. And individual submissions would be in the table assignment_submissions.
If none of this works, hopefully you have a recent backup of the Moodle database that you can restore. If the tables are gone completely, I don't think that you will have any other options but to go to the most recent backup.
Good luck.
Assignment
Assignment Topic are not showing --- Very URGENT
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