[Reprint] Quick judgment of lossless connections

Principle: if there is (R1 1_r2)-> (R1-R2) or (R1 1_r2)-> (R2-R1) in F, decomposition of R1 and R2 is non-destructive.

 

 

Instance:

 

R (A, B, C, D, E), R function dependency set f = {A-> BC, CB-> E, B-> D, e-> }.

 

Determine whether r1 (A, B, C), R2 (A, D, E) are lossless connections.

 

 

 

Because there are only two relational modes, you can use shortcuts to determine.

 

R1 primary r2 = {A}, R1-R2 = {B, c}, because f contains a-> BC, that is, (R1 primary R2)-> (R1-R2) so R1 and R2.

 

Http://bbs.csdn.net/topics/280061378

 

Http://blog.163.com/?email protected]/blog/static/11135225920113114833493

 

Http://www.blogjava.net/wxqxs/archive/2009/05/12/277322.html

 

[Reprint] Quick judgment of lossless connections