1. JDBC – Java Database Connectivity

2. Querying with PreparedStatement
String queryStr =
"SELECT * FROM employee " +
"WHERE superssn= ? and salary > ?";
PreparedStatement pstmt = con.prepareStatement(queryStr);
pstmt.setString(1, " ");
pstmt.setInt(2, 26000);
ResultSet rs = pstmt.executeQuery();

3. Statements vs. PreparedStatements: Be Careful!
Are these the same? What do they do?
String val = "abc";
PreparedStatement pstmt = con.prepareStatement("select * from R where A=?");
pstmt.setString(1, val);
ResultSet rs = pstmt.executeQuery();
String val = "abc";
Statement stmt = con.createStatement( );
ResultSet rs =
stmt.executeQuery("select * from R where A=" + val);

4. ResultSet
ResultSet objects provide access to the tables generated as results of executing a Statement queries
Only one ResultSet per Statement can be open at the same time!
The table rows are retrieved in sequence
A ResultSet maintains a cursor pointing to its current row
The next() method moves the cursor to the next row

5. executeQuery() no assumption is made on the validity of the query
ResultSet
executeQuery(String sql)
Executes the given SQL statement, which returns a single ResultSet object
no assumption is made on the validity of the query
if the SQL execute successfully it returns a ResultSet object containing rows from the database
if the SQL fails it will raise a SQLException

6. Executing a Statement - Example
ResultSet rs =
stmt.executeQuery(“select name from pets”);
ResultSet:
Initial cursor position
Fluffy
Claws
Buffy
Fang
Chirpy
Whistler
Slim
Puffball
next()
next()

7. ResultSet Object A table of data representing a database result set
maintains a cursor pointing to its current row of data
Initially the cursor is positioned before the first row
The next() method moves the cursor to the next row
next() returns false when there are no more rows in the ResultSet object
A default ResultSet object is not updatable and has a cursor that moves forward only
table of data representing a database result set, which is usually generated by executing a statement that queries the database.
A ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row. The next method moves the cursor to the next row, and because it returns false when there are no more rows in the ResultSet object, it can be used in a while loop to iterate through the result set.
A default ResultSet object is not updatable and has a cursor that moves forward only. Thus, you can iterate through it only once and only from the first row to the last row. It is possible to produce ResultSet objects that are scrollable and/or updatable.

8. Moving Through the ResultSet -Example
while (rs.next()) {
System.out.println(rs.getString((1))); }
Fluffy
Claws
Buffy
Fang
Chirpy
Whistler
Slim
Puffball

9. Basic Getter Methods int getInt(int columnIndex)
int getInt(String columnName)
String getString(int columnIndex)
String getString(String columnName)
Date getDate(int columnIndex)
Date getDate(String columnName)

10. ResultSet Methods boolean next() void close() activates the next row
the first call to next() activates the first row
returns false if there are no more rows
void close()
disposes of the ResultSet
allows you to re-use the Statement that created it
automatically called by most Statement methods

11. ResultSet Methods
Type getType(int columnIndex)
returns the given field as the given type
indices start at 1 and not 0!
Type getType(String columnName)
same, but uses name of field
less efficient
For example: getString(columnIndex), getInt(columnName), getTime, getBoolean, getType,...
int findColumn(String columnName)
looks up column index given column name

12. ResultSet Methods
JDBC 2.0 includes scrollable result sets. Additional methods included are : ‘first’, ‘last’, ‘previous’, and other methods.

13. ResultSet Example Statement stmt = con.createStatement();
ResultSet rs = stmt. executeQuery("select lname,salary from Employees");    
// Print the result
while(rs.next()) {  System.out.print(rs.getString(1) + ":");  System.out.println(rs.getDouble(“salary")); }

14. Mapping Java Types to SQL Types
SQL type Java Type
CHAR, VARCHAR, LONGVARCHAR String
NUMERIC, DECIMAL java.math.BigDecimal
BIT boolean
TINYINT byte
SMALLINT short
INTEGER int
BIGINT long
REAL float
FLOAT, DOUBLE double
BINARY, VARBINARY, LONGVARBINARY byte[]
DATE java.sql.Date
TIME java.sql.Time
TIMESTAMP java.sql.Timestamp

15. Cleaning Up After Yourself
Remember to close the Connections, Statements, Prepared Statements and Result Sets
con.close();
stmt.close();
pstmt.close();
rs.close()

16. DEMO