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In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not typically used to join multiple tables.
One method of copying an object is the shallow copy.In that case a new object B is created, and the fields values of A are copied over to B. [3] [4] [5] This is also known as a field-by-field copy, [6] [7] [8] field-for-field copy, or field copy. [9]
A database relation (e.g. a database table) is said to meet third normal form standards if all the attributes (e.g. database columns) are functionally dependent on solely a key, except the case of functional dependency whose right hand side is a prime attribute (an attribute which is strictly included into some key).
For purposes of duplicate removal the INTERSECT operator does not distinguish between NULLs. The INTERSECT operator removes duplicate rows from the final result set. The INTERSECT ALL operator does not remove duplicate rows from the final result set, but if a row appears X times in the first query and Y times in the second, it will appear min ...
8,060 bytes / 2 TB 6: 1,024 / 30,000(with sparse columns) 2 GB / Unlimited (using RBS/FILESTREAM object) 2 GB 6: 126 bits 2: 0001 9999 128 Microsoft SQL Server Compact (Embedded Database) 4 GB 4 GB 8,060 bytes 1024 2 GB 4000 154 bits 0001 9999 128 Mimer SQL: Unlimited Unlimited 16000 (+lob data) 252 Unlimited 15000 45 digits 0001-01-01 9999-12 ...
Microsoft Access is a database management system (DBMS) from Microsoft that combines the relational Access Database Engine (ACE) with a graphical user interface and software-development tools.
In computer programming, duplicate code is a sequence of source code that occurs more than once, either within a program or across different programs owned or maintained by the same entity. Duplicate code is generally considered undesirable for a number of reasons. [ 1 ]
Copy-on-write (COW), also called implicit sharing [1] or shadowing, [2] is a resource-management technique [3] used in programming to manage shared data efficiently. Instead of copying data right away when multiple programs use it, the same data is shared between programs until one tries to modify it.