QUESTION 17 HAPPY INSURANCE Observe the HAPPY INSURANCE DATABASE: CLIENT Clienti

Question

QUESTION 17 HAPPY INSURANCE Observe the HAPPY INSURANCE DATABASE: CLIENT ClientiD ClientName ClientAgent C111 C222 C333 C444 C555 C666 C777 ClientSpouseName Tom Karin Cole Dorothy Andy Tina Christina A1 A1 A2 A3 ?? Matt AGENT AgentName AgentArea AgentRating AgentYearofHire supervisedBy Agentip A1 A2 ?? A4 1990 2009 1992 2010 Kate 101 A1 100 Luke James ?? ArealD AreaName AreaHQ West Central Boston San Francisco Chicago This database will be used for the following questions citing tables from the HAPPy INSURANCE database How many records will the following query in the HAPPY INSURANCE database return? SELECT DISTINCT table name FROM user tab columns 10

Explanation / Answer

Let's begin with answer,

The query above is used to count number of tables. ANSWER = 3.

Explaination:

'table_name' indicates names of tables inside a database: CLIENT, AGENT, AREA.

'user_tab_columns' represents all the columns of the tables which are owned by user user executing query.

On executing query without DISTINCT keywords output would be:

table_name
------------------
CLIENT /*corresponding to ClientID*/
CLIENT /*corresponding to ClientName*/
CLIENT /*corresponding to ClientAgent*/
CLIENT /*corresponding to ClientSpouseName*/
AGENT /*corresponding to AgentID*/
AGENT /*corresponding to AgentName*/
AGENT /*corresponding to AgentArea*/
AGENT /*corresponding to AgentRating*/
AGENT /*corresponding to AgentYearOfHire*/
AGENT /*corresponding to SupervisedBy*/
AREA /*corresponding to AreaID*/
AREA /*corresponding to AreaName*/
AREA /*corresponding to AreaHQ*/

But using DISTINCT only table_name of certain table will only be in output once.

Output with DISTINCT:

table_name
----------------------
CLIENT
AGENT
AREA

Hence,

QUERY: SELECT DISTINCT table_name FROM user_tab_columns outputs 3 records.

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