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OCPJP709.3
Cert Obj Submit Queries and Read Results from DB
[9.3.1] What are the steps? | a) Get Connection b) Create statement c) Execute query d) Process results |
[9.3.2] Which ones return an int? | SQL INSERT, UPDATE,DELETE commands, or any of the SQL Data Definition Language (DDL) statements, like CREATE TABLE, return either the number of rows affected by the query or 0 //executeUpdate(),and execute() |
[9.3.3] Which ones return a ResultSet? | ResultSet rs = stmt.executeQuery("SELECT * from Customer");// executeQuery() |
[9.3.4] When Statement? | when you need to send a SQL statement to the database without any parameter. In normal cases, you need to use this interface only. You can create an instance of Statement using the createStatement() method in the Connection interface. |
[9.3.5] When PreparedStatement (subclass of Statement)? | represents precompiled SQL statement that can be customized using IN parameters. Used to improve performance, if SQL statement is executed multiple times.can get an instance of PreparedStatement by calling preparedStatement() method in Connection. |
[9.3.6] When CallableStatement (extends PreparedStatement) ? | used to execute 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. |
[9.3.7] Statement interface | The Statement interface provides three execute methods: executeQuery(), executeUpdate(),and execute() |
[9.3.8] ResultSet | call next() to read the first row, and so on |
[9.3.9]Closure | when execute() is executed or Statement is closed, all opem ResultSets are also closed. when connection is closed, all Statement and ResultSet are closed |
[9.3.10]ResultSet | numbered from 1, read-only, forward only, fetch size can be controlled |