SQL writing for 10 June 2024
Relation = A relation represents a file that stores data. It’s also known as a table.
Domain = The domain is a set of acceptable values that a column is allowed to contain.
E.g.: In the ID column, it’s not possible to store values such as “John” or “001”.
A record, also known as a tuple, is a row within a table.
Degree = A student table that stores the student's name, address, phone number and email address would have a degree of four.
Cardinality = you have 100 students in your student table, then that table has a cardinality of 100.
CONSTRAINT
1.Key constraints = there can’t be two students with the same Student ID.
Domain constraints = if an attribute requires a numeric value to be entered, and the value you are attempting to enter uses letters instead of numbers, then it would be invalid.
Referential integrity constraints = , there must be matching values in the two tables for that attribute.
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