What is the difference between Views and Materialized Views in Oracle?
Materialized views are disk based and are updated periodically based upon the query definition. Views are virtual only and run the query definition each time they are accessed.
relational-database
Algebra Relational sql GROUP BY SORT BY ORDER BY
Neither is possible in relational algebra but people have been creating some “extensions” for these operations (Note: in the original text, part of the text is written as subscript). GROUP BY, According to the book Fundamentals of Database Systems (Elmasri, Navathe 2011 6th ed): Another type of request that cannot be expressed in the basic … Read more
MS Access error: relationships must be on same number of fields with the same data types
Make sure you have your VendorID set as the same datatype in both the tables. N.B: Even if it is stored as a number, make sure they are both long integers. The duplicates shouldn’t prevent you from creating a relationship: duplicates restrict only when you try and create a relationship with referential integrity.
Difference between one-to-many and many-to-one relationship
Yes, it a vice versa. It depends on which side of the relationship the entity is present on. For example, if one department can employ for several employees then, department to employee is a one to many relationship (1 department employs many employees), while employee to department relationship is many to one (many employees work … Read more
Decomposing a relation into BCNF
Although the question is old, the other questions/answers don’t seem to provide a very clear step-by-step general answer on determining and decomposing relations to BCNF. 1. Determine BCNF:For relation R to be in BCNF, all the functional dependencies (FDs) that hold in R need to satisfy property that the determinants X are all superkeys of … Read more