31 votes 31 votes Which normal form is considered adequate for normal relational database design? $2NF$ $5NF$ $4NF$ $3NF$ Databases gate1998 databases database-normalization easy + – Kathleen asked Sep 25, 2014 • edited Feb 9, 2018 by dj_1 Kathleen 10.6k views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply Niraj Singh 2 commented Jun 19, 2017 reply Follow Share in the question "adequate normalization method" is asked for real database design ,not " which is best one". i think "adequate means "not more and not less but sufficient" even though BCNF will have no redundancy while 3NF will have some . but still 3NF is adequate for database design because of following reasons 1) BCNF may cause "loss of dependency" 2) to obtain BCNF , we may require to split relation into smaller one and its number can be huge in large database .which leads to complex maintenance . while in 3NF , even though some redundancies are there but it is better to have some redundancies than having above two problems of BCNF 1 votes 1 votes deepaksing commented May 6, 2021 reply Follow Share 3NF removes all the anomalies. So 3Nf is considered adequate for relational database dedign. But then also BCNF is more better than 3NF. But here we are asked adequate one so 3NF is adequate 0 votes 0 votes Please log in or register to add a comment.
2 votes 2 votes BCNF doesn't guarantee dependency preservation. Digvijay Pandey answered Aug 31, 2015 Digvijay Pandey comment Share Follow See all 6 Comments See all 6 6 Comments reply Show 3 previous comments Digvijay Pandey commented Sep 4, 2015 reply Follow Share "1st priority is Non Redundancy". reference ?? 0 votes 0 votes ANI commented Sep 4, 2015 reply Follow Share respected sir , here is the video i saw it in neptel heard. this topic is covered at 30.02 minutes.plz clarify my doubt if i misunderstood it. here at a point the professor says we thought of decomposing due to redundancy 0 votes 0 votes smsubham commented Aug 16, 2017 reply Follow Share @ANI We want to reduce redundancy, but lossless join and dependency preservation are more important. Why we reduce redundancy? To save space and avoid anomaly. But if our database becomes inconsistent in this, it will be of no use. Suppose you save 1 GB space but you lose thousands of customer informmation. What will you prefer? Information r8? 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Answer- Option D BCNF sdpshaw answered Oct 19, 2015 sdpshaw comment Share Follow See all 2 Comments See all 2 2 Comments reply LeenSharma commented Oct 19, 2015 reply Follow Share Yes, i got the same answer because redundancy is less in BCNF compare to other Normal forms. But Given answer is 3NF. 0 votes 0 votes smsubham commented Aug 16, 2017 reply Follow Share The answer is 3NF. As we cannot have a lossless join always to BCNF. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes There is not always a decomposition into BCNF i.e lossless and dependency preserving. So 3 NF. Cruise Device answered Jan 18, 2016 Cruise Device comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Ans: D rishu_darkshadow answered Sep 20, 2017 rishu_darkshadow comment Share Follow See all 6 Comments See all 6 6 Comments reply Show 3 previous comments SPluto commented Dec 28, 2018 reply Follow Share @ Shivani gaikawad The reason we want to preserve dependencies, is that each dependency represents a constraint on the database, and this constraint must be obeyed by the data in the DB. When a relation is decomposed, if some dependency is not preserved, then to check whether the data follows that lost constraint or not, we need to perform a join on the sub-relations to get back the original relation, just so that we can check if the constraint is satisfied. So if we ensure that dependencies are preserved, then we don't need to perform a join to check constraints. 10 votes 10 votes debasree88 commented Apr 23, 2019 reply Follow Share @SPluto thanks your explanation cleared my doubts 1 votes 1 votes Aks9639 commented Oct 20, 2019 reply Follow Share very nice @SPluto So even after decomposition database Relation meaning doesn't change, i.e. NO CHANGES IN ORIGINAL CONSTRAINTS. that's thing which i liked in GATE OVERFLOW 0 votes 0 votes Please log in or register to add a comment.