Use of CASCADE CONSTRAINTS in SQL

Question

What is use of CASCADE CONSTRAINTS in SQL?

Shankar M · Answer

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-qformat:yes;mso-style-parent:"";mso-padding-alt:0in 5.4pt 0in 5.4pt;mso-para-margin-top:0in;mso-para-margin-right:0in;mso-para-margin-bottom:10.0pt;mso-para-margin-left:0in;line-height:115%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:"Times New Roman";mso-fareast-theme-font:minor-fareast;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;} Hi Sharad, Cascade Constraints, are usually used when there exists a parent-child relationship between tables using foreign key or referential constraints defined. For Example, In case of deletion a record from the Parent Table, where there exists a foreign key to the child table, If you do not specify cascading deletes, the default behavior of the database prevents us from deleting data in the Parent table if the child table has a reference to the Parent.

Satyapriya Nayak · Answer

http://msdn.microsoft.com/en-us/library/aa933119%28v=sql.80%29.aspx http://msdn.microsoft.com/en-us/library/ms186973%28v=sql.105%29.aspx By using cascading referential integrity constraints, you can define the actions that the SQL Server takes when a user tries to delete or update a key to which existing foreign keys point.