Primary Keys in SQL Server – Definition, Syntax, Examples
原文英文，约1700词，阅读约需7分钟。发表于：。A primary key is a unique identifier for each record within a table that prevents duplicate values and allows for efficient data retrieval and manipulation. As such, a primary key is one of the fundamental elements of the database design. In this article, we'll explore the specifics of the primary key in SQL Server, discussing its types and usage. The post Primary Keys in SQL Server – Definition, Syntax, Examples appeared first on Devart Blog.
主键是数据库表中每个记录的唯一标识符，防止重复值并允许高效检索和操作数据。每个表只允许一个主键，主键名称格式为PK_<TableName>，最大长度为900字节，值必须唯一且不允许重复，所有列必须设置为NOT NULL。创建主键还会创建唯一的聚集索引。可以使用ALTER TABLE命令创建、删除和修改主键。主键与唯一键的区别在于主键不允许NULL值，而唯一键可以接受NULL值。
