Why do spurious tuples occur in the result of joining the EMP_PROJ1 and EMPLOCS relations of Figure 15.5 (result shown in Figure 15.6)?
What will be an ideal response?
In EMP_LOCS, a tuple (e, l) signifies that employee with name e works on some project
located in location l. In EMP_PROJ1, a tuple (s, p, h, pn, l) signifies that employee with
social security number s works on project p that is located at location l. When we join
EMP_LOCS with EMP_PROJ1, a tuple (e, l) in EMP_LOCS can be joined with a tuple (s,
p, h, pn, l) in EMP_PROJ1 where e is the name of some employee and s is the social
security number of a different employee, resulting in spurious tuples. The lossless join
property (see Chapter 13) can determine whether or not spurious tuples may result
based on the FDs in the two relations being joined.
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