Breast cancer may cause swollen axillary lymph nodes since the lymph vessels of the breast drain into the lymph nodes of the armpit. These nodes become enlarged when cancer cells spread beyond the breast tissue.
Relational database. (Redirected from Database constraints) A relational database is a digital database whose organization is based on the relational model of data, as proposed by E. F. Codd in 1970. The various software systems used to maintain relational databases are known as a relational database management system (RDBMS).
SQL Server supports the following classes of constraints: NOT NULL specifies that the column does not accept NULL values. For more information, see Allowing Null Values. CHECK constraints enforce domain integrity by limiting the values that can be put in a column. For more information, see CHECK Constraints. A CHECK constraint specifies a Boolean (evaluates to TRUE, FALSE, or unknown) search condition that is applied to all values that are entered for the column. All values that evaluate to FALSE are rejected. You can specify multiple CHECK constraints for each column.