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Select is denoted by which symbol? |
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Project is denoted by which symbol? |
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σ cnum = 573 (customer)
What does the degree = ? |
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σ cnum = 573 (customer)
What does the cardinality = ? |
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What does Project select? |
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How do you find the degree of a Cross Product? |
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Definition
# of elements of 1st relation + # of elements of 2nd relation |
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How do you find the cardinality of a Cross Product? |
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Definition
# of elements of 1st relation x # of elements of 2nd relation |
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Do you include the common attribute in an equijoin or natural join? |
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To be Union Compatible, what two requirements must be satisfied? |
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Definition
They must have the same degree & the data types must match |
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Part_Plumb ← π (pnum)(σclass =“PL”(part))
All_Orders ← π(ordernum,pnum) (orderline)
What would the result be? |
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Definition
Result ← All_Orders ÷ part_plumb |
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Term
temp = ordernum
Part_Plumb ← π (pnum)(σclass = “PL”(part))
All_Orders ← π(ordernum,pnum)(orderline)
temp2 ← ordernum(Part_Plumb X T1) - All_Orders
What would the result be? |
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Term
| List all the publishers that are not in New York. |
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Definition
| project pname ← (city !=(New York)(Publisher)) |
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| A collection of data which is related |
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| A known fact about something |
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| A universe of discourse with varying complexity. |
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| What is a database management system? |
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Definition
| A collection of programs that allow you to define, create, & manipulate a database |
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| Structured Query Language |
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| What does data redundancy lead to? |
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Definition
| It leads to wasted space and data inconsistency |
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What are the advantages of the DBMS approach? |
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Definition
- Avoids unwanted data redundancy/controlled redundancy
- Data inconsistency is much less probable
- Represents complex relationships among data
- Enforce integrity constraint
- Sharing of data (concurrency controls)
- Provides data independence
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Term
| What are the advantages of the DBMS approach that is data related? |
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Definition
controlled redundancy
sharing of data
providing multiple user views
consistency
providing data independence
enforcing integrity constraints |
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Term
| What are the advantages of he DBMS approach that are system related? |
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Definition
security - restricting unauthorized access
concurrency controls
providing structures for efficient query processing
providing backup & recovery. |
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