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iddu
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iddu
@1drie5
somehow trying to get into tech while having a lot of skill issues
Katılım Mart 2023
210 Takip Edilen114 Takipçiler
Alright twitter fammmmm suggest good bio for my pageeee single line bio looks kinda boring nowww
Rakhshan 💫@specsdotdesign
I have been constantly growing on Instagram and I never imagined getting so many compliments and genuine appreciation from people upon my content and creativity. But, in the end I owe this success to the people I found here on Twitter. It's crazy how I found so many amazing people who motivated me to start an Instagram page and even before that when I did a face reveal here on Twitter all these people supported me since day One. I'm truly grateful for my entire twitter family and most importantly I can't emphasize it enough that you need to put yourself out there. You might look dumb for a moment or two but the compound effect of showing up everyday will make you ahead of a lot of people.
English
L59
db transactions preserve acid via read/write ops.
lifecycle:
active → partially committed → committed
(or → failed → aborted)
concurrency control uses:
• locking protocols (e.g., 2pl)
• timestamp ordering
to ensure serializable execution.
#DBMS #SQL #Databases
iddu@1drie5
L58 minimal cover (canonical cover) eliminates redundant functional dependencies. algorithm: 1. decompose rhs (singleton rule). 2. remove extraneous attributes from lhs determinants. 3. remove redundant fds (if y ∈ x+ without x->y, discard). #DBMS #SQL #Databases
English
L58
minimal cover (canonical cover) eliminates redundant functional dependencies.
algorithm:
1. decompose rhs (singleton rule).
2. remove extraneous attributes from lhs determinants.
3. remove redundant fds (if y ∈ x+ without x->y, discard).
#DBMS #SQL #Databases
iddu@1drie5
L57 functional dependency sets f and g are equivalent (f ≡ g) iff f+ = g+, meaning f covers g and g covers f. algorithm: 1. for every (x->y) in g, verify y exists in x+ under f. 2. for every (x->y) in f, verify y exists in x+ under g. #DBMS #SQL #Databases
English
L57
functional dependency sets f and g are equivalent (f ≡ g) iff f+ = g+, meaning f covers g and g covers f.
algorithm:
1. for every (x->y) in g, verify y exists in x+ under f.
2. for every (x->y) in f, verify y exists in x+ under g.
#DBMS #SQL #Databases
iddu@1drie5
L56 algorithm to normalize a database relation: 1. find candidate keys. 2. 1nf: atomic values. 3. 2nf: zero partial dependencies. 4. 3nf: for x->y, x is a superkey or y is prime. 5. bcnf: x must be a superkey. decompose on violations. #DBMS #SQL #Databases
English
L56
algorithm to normalize a database relation:
1. find candidate keys.
2. 1nf: atomic values.
3. 2nf: zero partial dependencies.
4. 3nf: for x->y, x is a superkey or y is prime.
5. bcnf: x must be a superkey.
decompose on violations.
#DBMS #SQL #Databases
iddu@1drie5
L55 find the highest normal form sequentially: 1. compute candidate keys. 2. classify prime vs non-prime attributes. 3. evaluate: • 2nf: zero partial dependencies • 3nf: for x->y, x is superkey or y is prime • bcnf: x must be a superkey #DBMS #SQL #Databases
English
L55
find the highest normal form sequentially:
1. compute candidate keys.
2. classify prime vs non-prime attributes.
3. evaluate:
• 2nf: zero partial dependencies
• 3nf: for x->y, x is superkey or y is prime
• bcnf: x must be a superkey
#DBMS #SQL #Databases
iddu@1drie5
L54 5nf (project-join normal form) requires a schema to be in 4nf where every join dependency is implied by candidate keys. it resolves anomalies where a relation must be losslessly decomposed into 3 or more tables, rather than 2. #DBMS #SQL #Databases
English
L54
5nf (project-join normal form) requires a schema to be in 4nf where every join dependency is implied by candidate keys.
it resolves anomalies where a relation must be losslessly decomposed into 3 or more tables, rather than 2.
#DBMS #SQL #Databases
iddu@1drie5
L53 4nf requires a schema to be in bcnf with zero multivalued dependencies (mvds). an mvd (x ->-> y) exists when one attribute determines multiple independent values. grouping them forces cartesian products. fix by decomposing. #DBMS #SQL #Databases
English
L53
4nf requires a schema to be in bcnf with zero multivalued dependencies (mvds).
an mvd (x ->-> y) exists when one attribute determines multiple independent values. grouping them forces cartesian products. fix by decomposing.
#DBMS #SQL #Databases
iddu@1drie5
L52 Dependency Preserving Decomposition ensures functional dependencies can be enforced locally in decomposed tables. Rule: (F1 ∪ F2)+ = F+ If verifying an FD requires joins between decomposed tables, it may not be dependency preserving. #DBMS #SQL #Databases
English
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L52
Dependency Preserving Decomposition ensures functional dependencies can be enforced locally in decomposed tables.
Rule: (F1 ∪ F2)+ = F+
If verifying an FD requires joins between decomposed tables, it may not be dependency preserving.
#DBMS #SQL #Databases
iddu@1drie5
L51 lossless decomposition reconstructs relation r via natural join (r1 ⨝ r2 = r). lossy creates spurious tuples. rule: the intersecting attributes (r1 ∩ r2) must form a candidate or superkey in r1 or r2. #DBMS #SQL #Databases
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