HAPPY INSURANCE Observe the HAPPY INSURANCE DATABASE: CLIENT ClientID ClientName
ID: 3777413 • Letter: H
Question
HAPPY INSURANCE
Observe the HAPPY INSURANCE DATABASE:
CLIENT
ClientID ClientName ClientAgent ClientSpouseName
C111 Tom A1 Jenny
C222 Karin A1 Bill
C333 Cole A2 Amy
C444 Dorothy A2
C555 Andy A3 Amy
C666 Tina A3 Matt
C777 Christina A4 Mike
AGENT
AgentID AgentName AgentArea AgentRating AgentYearOfHire SupervisedBy
A1 Kate 1 101 1990
A2 Amy 2 92 2009 A1
A3 Luke 3 100 1992
A4 James 3 90 2010 A3
AREA
AreaID AreaName AreaHQ
1 East Boston
2 West San Francisco
3 Central Chicago
This database will be used for the following question citing tables from the HAPPY INSURANCE database.
If a DBMS enforces a DELETE RESTRICT option on the referential integrity constraint between CLIENT and AGENT in the HAPPY INSURANCE database, what will be the outcome after a user tries to delete the last record (A4, James, 3, 90, 2010, A3) from AGENT?
CLIENT will have 7 records
AGENT will have 4 records
CLIENT will have 6 records
AGENT will have 3 records
CLIENT will have 7 records
AGENT will have 3 records
CLIENT will have 6 records
AGENT will have 4 records
CLIENT will have 7 records
AGENT will have 4 records
CLIENT will have 6 records
AGENT will have 3 records
CLIENT will have 7 records
AGENT will have 3 records
CLIENT will have 6 records
AGENT will have 4 records
Explanation / Answer
The DELETE RESTRICT command ensures that the parent is deleted but not the children. It means that a given parent row can’t be deleted if a child row exists that references the value for that parent row. If there exists a parent row that does not reference child rows, then parent row can be deleted.
In the HAPPY INSURANCE DATABASE, the parent table is AGENT (Because the primary key AgentID is unique in this table )and the referenced table(child) is CLIENT, then according to the question, the deleted record is (A4, James, 3, 90, 2010, A3) and the deletion takes place from the child table. The primary key is AgentID and the reference takes place in the CLIENT table, having the foreign key as ClientAgent.
In this case, the deletion is taking place from the parent table but not the child table. So, it will not affect the number of records. Neither the parent table, nor the child table will be affected.
So, the correct option is CLIENT will have 7 records
AGENT will have 4 records
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