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).
Column and Table Constraints. Constraints can be column constraints or table constraints. A column constraint is specified as part of a column definition and applies only to that column. The constraints in the previous examples are column constraints.QL 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.