Lossless Decomposition

  • if forms a superkey for either R1 or R2, the decomposition of R is a lossless decomposition
  • 关系模式 R(U) 的分解 r={R1,R2},则 r 是一个无损连接分解的充要条件是 R1∩R2->R1-R2(或 R1∩R2->R2-R1)成立

BCNF Decomposition

Break large into multiple superkey.