Abstract
The “UPDATE” is part of SQL’s data manipulation language (DML) and is used for changing one or more tuples in a table.
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References
J. Krüger, C. Kim, M. Grund, N. Satish, D. Schwalb, J. Chhugani, H. Plattner, P. Dubey, A. Zeier, Fast updates on read-optimized databases using multi-core cpus. PVLDB 5(1), 61–72 (2011)
H. Plattner, in A common database approach for OLTP and OLAP using an in-memory column database, ed. by U. Çetintemel, S. Zdonik, D. Kossmann. SIGMOD Conference (ACM, Newyork, 2009), pp. 1–2
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Self Test Questions
Self Test Questions
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1.
Status Update Realization
How do we want to realize status updates for binary status variables?
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(a)
Single status field: “false” means state 1, “true” means state 2
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(b)
Two status fields: “true/false” means state 1, “false/true” means state 2
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(c)
Single status field: “null” means state 1, a timestamp signifies transition to state 2
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(d)
Single status field: timestamp 1 means state 1, timestamp 2 means state 2.
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(a)
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2.
Value Updates
What is a “value update”?
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(a)
Changing the value of an attribute
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(b)
Changing the value of a materialized aggregate
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(c)
The addition of a new column
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(d)
Changing the value of a status variable.
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(a)
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3.
Attribute Vector Rewriting after Updates
Consider the world population table (first name, last name) that includes all people in the world: Angela Mueller marries Friedrich Schulze and becomes Angela Schulze. Should the complete attribute vector for the last name column be rewritten?
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(a)
No, because ‘Schulze’ is already in the dictionary and only the valueID in the respective row will be replaced
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(b)
Yes, because ‘Schulze’ is moved to a different position in the dictionary
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(c)
It depends on the position: All values after the updated row need to be rewritten
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(d)
Yes, because after each update, all attribute vectors affected by the update are rewritten.
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(a)
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© 2013 Springer-Verlag Berlin Heidelberg
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Plattner, H. (2013). Update. In: A Course in In-Memory Data Management. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-36524-9_12
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DOI: https://doi.org/10.1007/978-3-642-36524-9_12
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