Alternate key

Alternate Key If any table have more than one candidate key , then after choosing primary key from those candidate key , rest of candidate keys are known as an alternate key of that table. Like here we can take a very simple example to understand the concept of alternate key. A replacement key is an alternate key that the system can display on forms instead of a meaningless numeric primary key value. Each table can have a maximum of one replacement key.

The replacement key is chosen by setting the ReplacementKey property on the table. The drop-down list offers every alternate key as an available value.

See Conventions for more details. By convention, an alternate key is introduced for you when you identify a property, that is not the primary key , as the target of a relationship. As we have seen in the candidate key guide that a table can have multiple candidate keys.

Among these candidate keys, only one key gets selected as primary key , the remaining keys are known as alternative or secondary keys. Lets take an example to understand the alternate key concept. A primary key may consist of real-world observables, in which case it is called a natural key , while an attribute created to function as a key and not used for identification outside the database is called a surrogate key.

Foreign: A key that has migrated to another entity. Alternate keys may be used like a primary key in a single-table select. At the most basic definition, a key is a unique identifier, so unique key is a pleonasm.

Creating Alternate Keys An alternate key is a key associated with one or more columns whose values uniquely identify every row in the table, but which is not the primary key. Keys that migrate to another entity may or may not be. For example, where the primary key for a table may be the employee i the alternate key might combine the first, middle, and last names of the employee. NAME, ID and CLASS are alternate keys.

There can be a key apart from primary key in a table that can also be a key. This key may or may not be a unique key. For example, in an employee table, empno is a primary key , empname is a alternate key that may not be unique but still helps in identifying a row of the table. Alternate Key : An alternate key (Alt key ) is a key that is present on most computer keyboards and is considered a modifier key that can used similarly to the shift or control keys.

In other words, the alternate key provides alternate input and operations when pressed in combination with other keys. Türkçe online sözlük Tureng. Kelime ve terimleri çevir ve farklı aksanlarda sesli dinleme. A primary key are the candidate key that you select to be used as the main key for that table.

All other candidate keys can be assigned as an alternate key. The Primary must be specified upon. The strategy is to rehabilitate affected irrigation systems and transportation and communication linkages using upgraded climate and disaster standards and specifications as well as build new redundant and alternate key infrastructure systems for improved resiliency, RDC Vice Chair and National Economic Development Authority (NEDA) Regional Director Severino Santos said. In addition to the primary key , you can code one or more alternate keys for a VSAM KSDS file. By using alternate keys, you can access an indexed file to read records in some sequence other than the prime- key sequence.

More than one record could be accessed if alternate keys are coded to allow duplicates. Composite alternate key in tables.

Ask Question Asked years, months ago. Active year, months ago. Assume that a table have columns A, B, C and D. The surrogate key is linked to the already existing RecId field within any table.

I want to just a use of Alternate Key in sql server that how can we use in our query and what is the actual logic of this.