Is a key field the same as a primary key?

Question

Is a key field the same as a primary key?

Answer 1

a key field is a field (or column) which is indexed and means that this column can be used to eaily find data



A primary key (PK) is, if you like an extension of that.. its a field or column that is indexed, but it is unique in the table. A primary key is a column which uniquely identifies that record, and is often used elsehwere as a foreign key in realtional databases



A foreign key (FK) is a value that identifies a unique value in another table. say you had a db identifying cars, you may have a car manufacturer table (eg Ford, BMW, Saab etc..) and a model table (eg Escort, Feista, Ka etc...)



the manufacturer table will have a primary key, which is replicated in the model table so that you know that Ford made the Excort, Rover made the SD1. there may be multiple occurances of the manufacturer ID in the model table, but only one instance in the manufacturer table



you can define keys that have unique values, but these aren't neccesarily the Priamry Key)



you can define keys that are comprised of muliple columns of fields, these can be primary keys, these can be 'just' indexed (although there is very little use in practise for composite keys that are NOT primary keys)



incidentally when designing tables sometimes its best to use an autogenerated primary key (a 'surroagte' key), sometimes its better to use an actual value (a 'natural' key). You would use a surrogate key if you couldn't find an appropriate natural key, or their were several contenders, or the natural key would be a complex composite key. In an ideal world you do not want your primary key to change, ideally never, but occasional is OK).... because changing a primary key would ential changing every value referrign to that key in every child table, and proiabbly banjax the indexes.



selecting whether to use a natural or surrogate key can cause fiifulties... histroically you would use a surroagte key for manufacturer (reason: primarily space), these days its perfectly acceptable to use say a code or even the value itself. In the car manufacturer table I wouldnt' use the full manufactiruer name, as you have the likes of Koenigzegg, but a code may be appropriate.. the reason it may save you time havign to do joins and lookups, it makes the data easier to read.. but ulitmately its personal choice

Answer 2

No. A key is a field which become a value to identify a row uniquely. but it may not be the case always. A primary key on the contrary is a field which can uniquely identify a row in a table

Answer 3

No, because you can get primary and secondary keys (I presume you're working with MS Access)

Answer 4

you will stay in hell putting Description as your common key container. they'll furnish as many as description opportunities they are able to circulate into. as quickly as possible set a container as common key that consumers ought to in no way touch and your device might look after.