Constraint can be applied to specify rules on a database. There are many constraints but we will only discuss the most commonly used in this blog post. 248 more words
Tags » Primary Key
Explanation of Constraints:
The NOT NULL constraint enforces a column to NOT accept NULL values.
This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field. 228 more words
Functional dependency (FD) is a set of constraints between two attributes in a relation. Functional dependency says that if two tuples have same values for attributes A1, A2,…, An, then those two tuples must have to have same values for attributes B1, B2, …, Bn. 1,188 more words
As explained in How does Cassandra store data? – A simple explanation Cassandra uses partitioning key (the first part of primary key) to store a record into a partition on a node. 141 more words
Pattern #4: Get rid of all OR operators from sql where clauses. For example, consider an SQL requirement to authenticate user by comparing the string entered by the user with either username… 76 more words