3i Infotech Papers: Sample Questions 995 - 996 of 1245
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Question number: 995
Question
Under which circumstance should you create an index on a table?
Choices
Choice (4) | Response | |
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a. | The table is small. |
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b. | The table is updated frequently. |
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c. | A columns values are static and contain a narrow range of values |
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d. | Two columns are consistently used in the WHERE clause join condition of SELECT statements. |
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Answer
d.Explanation
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Index on table is created when there are thousands of rows and user wants to search the record on some conditions.
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So indexes are created for where clauses- for columns used in the WHERE clauses or join conditions.
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Creating an index on an empty table has no performance implications at the time of creation but performance is affected when data is added to the table.
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Creating indexes on large tables should be planned to not affect database performance.
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Preferred way to create indexes on large tables is to start with the clustered index and then build no clustered indexes.
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Set the ONLINE option to ON when creating indexes on existing tables.
Question number: 996
Describe in Detail
How java can be connected to a database?
Explanation
There are steps to connect any java application with the database using JDBC.
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Register the driver class:
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The forName () method of class registers the driver class
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Method dynamically loads the driver class.
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Create the connection object:
- The getConnection () method of DriverManager class establishes connection with the database.
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Create the statement object:
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The createStatement () method of connection interface is used to create a SQL statement.
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Object of the statement executes queries with the database.
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Execute the query:
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The executeQuery () method of statement interface executes queries to the database.
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This method returns object of ResultSet which can get all the records of a table.
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Close the connection object:
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This is when statement and Result set will be closed automatically.
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The close () method of connection interface closes the connection.
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