In a database, "Key" and "Field" are two related concepts with different meanings.
Key (Key) usually refers to one or more fields used to uniquely identify each record in a database table . The main purpose of a key is to ensure that each record in a table has a unique identifier so that a particular record can be accurately identified and accessed during database operations. In a relational database, common key types include primary key (Primary Key) and foreign key (Foreign Key).
- A primary key is a unique identifier that uniquely identifies each record in a database table. A primary key can consist of one or more fields, but it must be guaranteed that each record in the entire table has a unique primary key value. Primary keys are often used to quickly find, sort, and join records in tables.
- A foreign key is a field in one table that references a primary key in another table. Foreign keys are used to establish relationships between tables and can be used to maintain data integrity and consistency. Through foreign keys, operations such as associated queries, cascading updates, and deletions between tables can be realized.
A field (Field) is a column in a database table that defines the type and attributes of the data stored in the table. Each field has a name and data type, and can define other attributes, such as allowing empty (NULL) or not allowing empty, default value, uniqueness constraints, and so on. Fields are used to describe each data element in a table, and each record contains a set of fields, each of which stores a specific data item.
To sum it up, a key is a unique identifier used to identify and relate records in a table, while a field is a single column in a table that stores data. Keys are an important mechanism for ensuring the uniqueness and association of data, while fields are the basic unit for defining and organizing data.
For specific examples, please refer to the following blog:
https://blog.csdn.net/github_35160620/article/details/52684234