If you never want to have duplicates, you should declare this as a table constraint: CREATE TABLE bookmarks( users_id INTEGER, lessoninfo_id INTEGER, UNIQUE(users_id, lessoninfo_id) ); (A primary key over both columns would have the same effect.) It is then possible to tell the database that you want to silently ignore records that would violate such … Read more
If you want to disable all constraints in the database just run this code: — disable all constraints EXEC sp_MSforeachtable “ALTER TABLE ? NOCHECK CONSTRAINT all” To switch them back on, run: (the print is optional of course and it is just listing the tables) — enable all constraints exec sp_MSforeachtable @command1=”print ‘?'”, @command2=”ALTER TABLE … Read more
SQL Server does simple counting of cascade paths and, rather than trying to work out whether any cycles actually exist, it assumes the worst and refuses to create the referential actions (CASCADE): you can and should still create the constraints without the referential actions. If you can’t alter your design (or doing so would compromise … Read more
C# does not support this. Hejlsberg has described the reasons for not implementing the feature in an interview with Bruce Eckel: And it’s not clear that the added complexity is worth the small yield that you get. If something you want to do is not directly supported in the constraint system, you can do it … Read more
If you want to learn, how to use regex, I recommend the following read your lecture notes read a Java book (especially the chapters about “Pattern” and “regular expressions”) read the Java documentation, e.g. about Pattern