JDBC

Question 1

What is the purpose of the driver manager?

Answer 1

it works as a directory of JDBC drivers - it maintains a list of available data source and their drivers. The driver manager chooses an appropriate driver to communicate with the respective DBMS.

Question 2

What is the general format of the JDBC URL?

Answer 2

jdbc: :

ie. jdbc:mysql://localhost:3306

Question 3

What is the DriverManager used for?

Answer 3

helps establish the connection between the program (the user) and the JDBC drivers

Question 4

What is the difference between Statement, PreparedStatement and CallableStatement?

Answer 4

Statement: Sends a SQL statement to the database without any parameters. For typical uses, you need to use this interface. You can create an instance of Statement using the createStatement() method in the Connection interface

PreparedStatement: Represents a precompiled SQL statement that can be customized using IN parameters. You can get an instance of PreparedStatement by calling the preparedStatement() method in the Connection interface

CallableStatement: Executes stored procedures. CallableStatement instances can handle IN as well as OUT and INOUT parameters. You need to call the prepareCall() method in the Connection interface to get an instance of this class

Question 5

What does a executeQuery() method returns?

Answer 5

returns a ResultSet

Question 6

What does a executeUpdate() method returns?

Answer 6

returns an update count

Question 7

What does a execute() method returns?

Answer 7

multiple ResultResets or multiple update counts or a combination of both

Question 8

What is the column index that the resultSet starts from?

Answer 8

1

Question 9

What are the two ways of updating the database?

Answer 9

queries or you can fetch a resultset using SQL query and then change the database

Question 10

What are the key interfaces of JDBC?

Answer 10

• Driver ( knows how to get a connection from the database)
• Connection (knows how to communicate with the database)
• Statement (knows how to run the SQL)
• Result (knows what was returned by the select query)

Question 11

What are the two ways of getting a connection?

Answer 11

DriverManager or DataSource

DriverManager.getConnection(“jdbc:derby:zoo”)

Question 12

How to obtain a statement?

Answer 12

stmt = conn.createStatement()

or

stmt = conn.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY

Question 13

What are the ResultSet Type options?

Answer 13

ResultSetType : Can go backwards : See latest data

• ResultSet.TYPE_FORWARD_ONLY : no : no
• ResultSet.TYPE_SCROLL_INSENSITIVE: yes : no
• ResultSet_TYPE_SCROLL_SENSITIVE : yes : yes

Question 14

What are the ResultSet ConcurrencyMode?

Answer 14

ResultSetType : can read data : can update data

• ResultSet.CONCUR_READ_ONLY : yes : no
• ResultSet.CONCUR_UPDATABLE: yes : yes

Question 15

How can you execute a statement?

Answer 15

Statement stmt = conn.createStatement()

int result = stmt.executeUpdate( “insert/update/delete”

or

ResultSet rs = stmt.executeQuery(“select * from species”);

Question 16

True or false

execute() can only execute queries

Answer 16

False

execute() can run either a query or an update

Question 17

True or false

Closing a connection does not close the statement and ResultSet

Answer 17

false

Closing a connection also closes statement and resultSet

Question 18

True or false

closing a statement also closes the ResultSet

Answer 18

true

Question 19

True or false

JDBC automatically closes a ResultSet when you run another SqlStatement

Answer 19

true

Question 20

Which are the required parts of a jdbc url?

Answer 20

jdbc and database name

Question 21

What file is required inside a jdbc 4.0+ drier jar?

Answer 21

META-INF/service/java.sql.Driver

Question 22

Which ones return boolean and which ones return void?

absolute(int)
relative(int)
previous()

afterLast()
beforeFirst()

Answer 22

boolean:

absolute(int)
relative(int)
previous()

void:

afterLast()
beforeFirst()

Question 23

What is the difference between PreparedStatement and CallableStatement?

Answer 23

A PreparedStatement is used for SQL statements that are executed multiple times with different values.

A CallableStatement is meant for executing a stored procedure, which has already been created in the database.

Question 24

What SQL standard must a JDBC compliant driver implement?

Answer 24

SQL92