3nf

问题 My database design is currently at stage 3NF. The issue that is of concern is the foreign keys and in some cases compound keys. My question is this: Can you move compound keys and/or foreign keys to create other tables provided the attributes associated with the compound keys/foreign keys do not rely on the primary key? I think the answer is yes due to this link: Are Foreign Keys included in Third Normal Form? Best Answer : Just because it's a foreign key doesn't mean it also can't be

问题 My database design is currently at stage 3NF. The issue that is of concern is the foreign keys and in some cases compound keys. My question is this: Can you move compound keys and/or foreign keys to create other tables provided the attributes associated with the compound keys/foreign keys do not rely on the primary key? I think the answer is yes due to this link: Are Foreign Keys included in Third Normal Form? Best Answer : Just because it's a foreign key doesn't mean it also can't be

问题 My database design is currently at stage 3NF. The issue that is of concern is the foreign keys and in some cases compound keys. My question is this: Can you move compound keys and/or foreign keys to create other tables provided the attributes associated with the compound keys/foreign keys do not rely on the primary key? I think the answer is yes due to this link: Are Foreign Keys included in Third Normal Form? Best Answer : Just because it's a foreign key doesn't mean it also can't be

来源： https://stackoverflow.com/questions/23681453/finding-a-relation-in-3nf-but-not-in-bcnf

问题 According to Wikipedia Today's Court Bookings Each row in the table represents a court booking at a tennis club that has one hard court (Court 1) and one grass court (Court 2) A booking is defined by its Court and the period for which the Court is reserved Additionally, each booking has a Rate Type associated with it. There are four distinct rate types: SAVER, for Court 1 bookings made by members STANDARD, for Court 1 bookings made by non-members PREMIUM-A, for Court 2 bookings made by

问题 I am implementing a many-to-many mapping in grails using 3NF, Not using the hasMany or belongsTo property. Taken from this article it shows and explains quite a lot about its advantages. Article: http://burtbeckwith.com/blog/?p=169 Presentation notes: http://burtbeckwith.com/blog/files/169/gorm%20grails%20meetup%20presentation.pdf I'm trying to make a Tag system onto questions, kind of like this(stackoverflow :)) I can save the Question and the Tags, then save the association with them, but

问题 I am writing a tag-based ASP.net system. Using the following db scheme: Topic <many-many> TagTopicMap <many-many> Tag Basically it is a 3NF approach (toxi) that I found from the following: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html Here is the code snippet I have: DataLoadOptions options = new DataLoadOptions(); options.LoadWith<Topic>(t => t.TagTopicMaps); options.LoadWith<TagTopicMap>(tt => tt.Tag); var db = new lcDbDataContext(); db.LoadOptions = options; db.Log =

问题 I am writing a tag-based ASP.net system. Using the following db scheme: Topic <many-many> TagTopicMap <many-many> Tag Basically it is a 3NF approach (toxi) that I found from the following: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html Here is the code snippet I have: DataLoadOptions options = new DataLoadOptions(); options.LoadWith<Topic>(t => t.TagTopicMaps); options.LoadWith<TagTopicMap>(tt => tt.Tag); var db = new lcDbDataContext(); db.LoadOptions = options; db.Log =

问题 Suppose a relation schema R(A,B,C) and the FDs are {A -> B, B -> C} So the superkeys are {A}, {A,B} Now if we decompose it into 3NF it will be R1(A,B) with FD {A -> B} and R2(B,C) with FD {B -> C} Is it in BCNF ? I can't determine. Since B was not a superkey in R does {B -> C} in R2 violates BCNF ? 回答1: {AB} is a superkey, but it's not a candidate key. (It's not a minimal superkey.) The decomposition R 1 ( A B) R 2 ( B C) is in at least BCNF. Informally, a relation is in BCNF if every arrow

问题 From the Database Management Systems book: given the relation SNLRWH (each letter denotes an attribute) and the following functional dependencies: S->SNLRWH (S is the PK) R->W My attempt: First, it is not 3NF: for the second FD, neither R contains W, nor R contains a key, nor W is part of a key. Second, it is/not 2NF. If we examine the second FD, W is dependent on R, which in turn is not part of a key. STUCK. 回答1: 2NF is violated if some proper subset of a candidate key appears as a