“Was ist der Schlüssel in SQL” Code-Antworten

Was ist der Schlüssel in SQL

A key is a single or combination of multiple fields in a table.
It is used to fetch or retrieve records/data rows from the data table 
according to the condition/requirement. Keys are also used to create
a relationship among different database tables or views.

The following are the list of SQL Keys:

Primary Key
Unique Key
Candidate Key
Alternate Key
Composite Key
Super Key
Foreign Key