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Question:(a) The objective of query optimization is to choose the most efficient strategy for implementing a given relational query, thereby improving the system performance. One of the stages of query optimization is to convert the internal form into equivalent and more efficient canonical form, using well-defined transformation rules. Two rules of the transformation rules is given below:Rule 1 - Transform a sequence of restrictions against a given relation into a single (ANDed) restriction.Rule 2 - Transform a restriction of a projection into a projection of a restriction.(i) Explain what is meant by each of the above rules.(ii) Using the relational schema given in Appendix, provide example of each of the above rules.(b) Refer to the relational schema given in Appendix.Assuming that: The Employee relation contains 1000 records among which 300 employee are assigned to departments located in the United States.- The Department relation contains 30 records among which 20 departments are located in United States- The Location relation contains 20 records among which 5 are situated in the United States.(i) Express the following query in SQL:"find the employee Last names and the department names who are working in United States (Location.country_id = US)(ii) Choose two possible methods to evaluate the query, and use the relational algebra to formulate clearly all the steps required in the evaluation. For each method, calculate the number of tuples for all the intermediate relations (namely, size of the intermediate relations) required for each step.
Negation (NOT, ¬) - SQL There are three rows instead of just two. As you can see, ¬ p is defined as in two-valued logic (2VL) when p is either true or false, but ¬ (unknown) i
Using %ROWTYPE The %ROWTYPE attribute gives a record type which represents a row in a table (or view). The record can store the whole row of data selected from the table or fetc
Delimiters A delimiter is a simple or compound symbol which has a special meaning to PL/SQL. For example, you use delimiters to symbolize an arithmetic operation like additio
Use of Table Comparisons - SQL Table comparisons where it is noted that although table expressions cannot be compared, we have TABLE (t) to convert a table expression t into
Using Pragma RESTRICT_REFERENCES: The function called from the SQL statements should obey certain rules meant to control the side effects. To check for violation of the rules,
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Using FIRST and LAST FIRST and LAST return the first and last (minimum and maximum) index numbers in a collection. When the collection is empty, the FIRST and LAST return NULL
LOB Types The large object (LOB) datatypes like BFILE, BLOB, CLOB, and NCLOB store the blocks of unstructured data (like graphic images, text, video clips, and sound waveforms)
Substitution and Instantiation - SQL It shows how NULL might appear in substitution for a parameter of a predicate and how it might thus participate in instantiation of that p
Effects of NULL for union - SQL The treatment of NULL in invocations of EXCEPT is as for UNION. This is different from its treatment in those of NOT IN and quantified compari
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