is a "table page" something like an imaginary row or something?

http://searchsqlserver.techtarget.com/tip/Differences-bet开发者_如何学Pythonween-varchar-and-nvarchar-in-SQL-Server:

The size for a table page is 8,196 bytes, and no one row in a table can be more than 8,060 characters. This in turn limits the maximum size of a VARCHAR to 8,000 bytes.

What exactly is a "table page"?

is a "table page" something like an imaginary row or something?

See this link for an explanation: Understanding Pages and Extents
Quote:

The fundamental unit of data storage in SQL Server is the page. The disk space allocated to a data file (.mdf or .ndf) in a database is logically divided into pages numbered contiguously from 0 to n. Disk I/O operations are performed at the page level. That is, SQL Server reads or writes whole data pages.

Here's another one: SQL Server data structures
Quote:

In SQL Server, data is organized in pages. A page has a fixed size (8 KB). Each page contains records. The number of records that can be stored in a page depends on the size of the records. The operation of reading data from a page is called a logical IO. The smaller the size of a record is, the more records can be read with the same number of logical IOs.

It's just a unit of space that the database engine uses internally to manage the database. Typically a database engine will read a database one page at a time. Some db engines thus say that a single record cannot cross two pages, or have other such restrictions. 99% of the time you don't even think about this when creating a database. There's a maximum size on a row in the table. Exactly what internals lead to that maximum aren't really very important to the typical database programmer.