JDBC

Question 1

relational database

Answer 1

a database that is organized into tables, which consist of rows and columns

Question 2

What do you have to know about SQL for the exam?

Answer 2

Pretty much nothing.

Just assume any SQL code that you see is valid.

Question 3

Driver interface

Answer 3

Knows how to get a connection to the database

Question 4

Connection interface

Answer 4

Knows how to communicate with the database

Question 5

Statement interface

Answer 5

Knows how to run the SQL

Question 6

ResultSet interface

Answer 6

Knows what was returned by a SELECT query

Question 7

JDBC URL format

Answer 7

jdbc:database_name:connection_details

The first part is jdbc. The second part is the name of the vendor/ product. The third part varies by database, but it includes the location and name of the database. The location is either localhost or an IP address followed by an optional port.

Question 8

How to create a Connection using DriverManager

Answer 8

DriverManager.getConnection(jdbc_url)

DriverManager.getConnection(
jdbc_url, “username”,
“password”);

Question 9

How to create a Statement from a Connection called conn

Answer 9

conn. createStatement()

conn. (ResultSet, ResultSet)

Question 10

What modes is a ResultSet in by default?

Answer 10

TYPE_FORWARD_ONLY and CONCUR_READ_ONLY

Question 11

ResultSet.TYPE_FORWARD_ONLY

Answer 11

You can go through the data once in the order in which it was retrieved.

Question 12

ResultSet.TYPE_SCROLL_INSENSITIVE

Answer 12

Allows you to go through the data in any order. You can go both forward and backward. You can even go to a specific spot in the data.

Note: there is another value TYPE_SCROLL_SENSITIVE that most databases don’t support.

Question 13

ResultSet.CONCUR_READ_ONLY

Answer 13

It means that you can’t update the result set.

Question 14

ResultSet.CONCUR_UPDATABLE

Answer 14

lets you modify the database through the ResultSet

Question 15

What method do you use to execute a SQL statement given Statement stmt?

Answer 15

For UPDATE, DELETE, and INSERT:

stmt.executeUpdate(sql_statement);

Returns the number of rows that were inserted, deleted, or changed.

For SELECT:

stmt.executeQuery(sql_statement);

Returns a ResultSet

For general use:

stmt.execute(sql_statement)

Returns a boolean that indicates whether or not it is a ResultSet

Question 16

How to loop through a ResultSet

Answer 16

while(rs.next())

Question 17

When talking about row/column numbers in JDBC, we start with 1, NOT 0

Answer 17

Just remember that

When talking about row/column numbers in JDBC, we start with 1, NOT 0

Question 18

Given type scroll insensitive ResultSet rs

rs.absolute(n)

Answer 18

Moves to the row number n. Returns a boolean saying if there is data in this row.

**Remember that rows start counting with 1

Note: A negative number means to start counting from the end of the ResultSet rather than from the beginning.

Question 19

Given type scroll insensitive ResultSet rs

rs.relative(n)

Answer 19

Moves n rows from the current row.

Question 20

What should you do once you are done with your Connections and Statements and ResultSets?

Answer 20

Close em, dude!

Or open them up in a try-with-resources statement to make them close automatically.

Question 21

JDBC automatically closes a ResultSet when…

Answer 21

you run another SQL statement from the same Statement.

Question 22

Order to close the JDBC components

Answer 22

ResultSet
Statement
Connection

Question 23

SQLException methods

getMessage()

getSQLState()

getErrorCode()

Answer 23

• returns a human-readable message as to what went wrong
• returns a code as to what went wrong
• returns a database-specific code