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25 Cards in this Set
- Front
- Back
If a logical model meets 4NF what can we assume about the model |
Undesirable functional dependencies have been resolved |
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Super key |
Unique |
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Candiate key |
Unique and irreducible |
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Non-trivial join dependencies |
Exist when there are 3 primary keys (3 underlined attributes) |
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Which syntax includes all the tuples from the left table and only matching tuples from the right |
Left join |
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Which syntax includes all tuples matching the left and right table |
Inner join |
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Which syntax includes all the tuples from both left and right, plus the matching information |
Full outer join |
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To meet the requirements for minimal cover, we could transform A-> (B,C) into how many dependencies? |
2 A ->B A->C |
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Normalization |
Validates a database design |
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The bottom-up approach for determining the candidate keys of a relation by iteratively adding attributes together to evaluate which combinations of attributes and functional dependencies can fully recreate the original relation is referred to as |
Synthesis |
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To preserve information during decomposition the database should |
Use lossless joins retain all attributes retail all functional dependencies retail all business rules |
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(Ensures that the value in a column meets a specific condition) Semantic Integrity constraints that deal with attribute-level conditions that are retained through the logical model are generally enforced by |
Check constraints |
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combination of a NOT NULL and UNIQUE. Ensures that a column (or combination of two or more columns) have a unique identity which helps to find a particular record in a table more easily and quickly |
PRIMARY KEY constraint |
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Ensures that each row for a column must have a unique value |
UNIQUE constraint |
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Indicates that a column cannot store NULL value |
NOT NULL constraint |
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Normalization accomplished through decomposition does what? |
Changes undesirable functional dependencies into desirable ones |
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conceptual database design |
1. evaluates relationships between entities 2. mostly based on intuition and semantics 3. Uses symbols and diagrams similar to flowcharts 4. typically retains some undesirable redundancy which can cause anomalies 5. Technology dependent |
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logical database design |
1. Evaluates relationships between attributes 2. Rooted in relational algebra 3. symbols typically appear more like equations 4. normalization eliminates almost all undesirable redundancies 5. Influenced by the limitations of the DBMS |
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From a conceptual perspective, violating a normal form requirement means |
Two different relations have been mistakenly specified as a single relation |
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If a table has resolved all anomalies caused by undesirable functional dependencies what normal form is it in |
3NF/BCNF |
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What is required to describe the conceptual necessity of 4NF |
It is possible to have anomalies due to 2 independent relationships between attributes with the same determinant |
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A table with 4 attributes that are all part of the primary key is in at least what normal form? |
3NF/BCNF |
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The entity integrity constraint possessed by a primary key and not a by a superkey or candidate key is? |
Not null |
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Using a surrogate key does which of the following |
Provides a way to uniquely identify all tuples |
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A table in 3NF has.. |
1. no multi-value attributes 2. No undesirable partial attributes 3. No undesirable transitive dependencies 4. eliminantes redundancy caused by undesirable functional dependencies |