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A table (called the referencing table) can refer to a column (or a group of columns) in another table (the referenced table) by using a foreign key. The referenced column(s) in the referenced table must be under a unique constraint, such as a primary key. Also, self-references are possible (not fully implemented in MS SQL Server though [5]).
A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table. The constraint must be a predicate . It can refer to a single column, or multiple columns of the table.
Column level encryption is a type of database encryption method that allows user to select specific information or attributes to be encrypted instead of encrypting the entire database file. To understand why column level encryption is different from other encryption methods like file level encryption , disk encryption , and database encryption ...
The main disadvantage associated with column-level database encryption is speed, or a loss thereof. Encrypting separate columns with different unique keys in the same database can cause database performance to decrease, and additionally also decreases the speed at which the contents of the database can be indexed or searched. [12]
Transparent Data Encryption (often abbreviated to TDE) is a technology employed by Microsoft, IBM and Oracle to encrypt database files. TDE offers encryption at file level. TDE enables the encryption of data at rest, encrypting databases both on the hard drive and consequently on backup media.
L is an optional label to be associated with the message (the label is the empty string by default and can be used to authenticate data without requiring encryption), PS is a byte string of k − m L e n − 2 ⋅ h L e n − 2 {\displaystyle k-\mathrm {mLen} -2\cdot \mathrm {hLen} -2} null-bytes.
Starting from the hash ("re3xes") in the image below, one computes the last reduction used in the table and checks whether the password appears in the last column of the table (step 1). If the test fails (rambo doesn't appear in the table), one computes a chain with the two last reductions (these two reductions are represented at step 2)
All columns are regular [i.e. rows have no hidden components such as row IDs, object IDs, or hidden timestamps]. Violation of any of these conditions would mean that the table is not strictly relational, and therefore that it is not in first normal form. Examples of tables (or views) that would not meet this definition of first normal form are: