I just started learning about MySQL and I am now trying to learn prepared statements. When I uses them, I get this error java.sql.SQLSyntaxErrorException. Can someone tell me where am I getting the syntax wrong? Thanks. Here is my code:
public class DBConnector {
private Statement statement;
private ResultSet result;
private PreparedStatement preparedStatement;
public void createDB() {
try {
sql = "CREATE DATABASE IF NOT EXISTS ?";
tableName = "test_name";
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, tableName);
int myResult = preparedStatement.executeUpdate();
if(myResult == 1){
System.out.println("Database successfully created.");
}else{
System.out.println("Database with that name already exists. Please try again with different name.");
createDB();
}
}catch (SQLException e) {
System.out.println("Database creation failed.");
e.printStackTrace();
}
}
}
We can't bind Database names in Query parameters.
Statement stmt=con.createStatement();
int rs=stmt.executeUpdate("CREATE DATABASE dbname");
Try in this way, Database will create.
Related
I'm working on a project in whose database I need to initialize a session variable. If I work directly with sql, the initialization is done with SET statement
set local app.user_id to "0000";
I try to initialize it with Connection#setClientInfo() but failed
try(Connection connection = getDataSource().getConnection()) {
boolean isAutoCommit = connection.getAutoCommit();
try {
Properties properties = new Properties();
properties.put("app.user_id", "0000");
connection.setAutoCommit(false);
connection.setClientInfo(properties);
String query = "insert into positions (name, description) values (?, ?)";
try(PreparedStatement statement = connection.prepareStatement(query)) {
statement.setString(1, position.getName());
statement.setString(2, position.getDescription());
statement.executeUpdate();
}
connection.commit();
}
catch (SQLException e) {
e.printStackTrace();
connection.rollback();
}
finally {
connection.setAutoCommit(isAutoCommit);
}
}
I get PSQLException (insert query is dependent on parameter and it does not pass)
org.postgresql.util.PSQLException: ERROR: unrecognized configuration parameter "app.user_id"
If I use PreparedStatement I get PSQLException with message ERROR: syntax error at or near "$1"
try(Connection connection = getDataSource().getConnection()) {
boolean isAutoCommit = connection.getAutoCommit();
try {
connection.setAutoCommit(false);
try(PreparedStatement statement = connection.prepareStatement("set local app.user_id to ?")) {
statement.setString(1, "0000");
statement.execute();
}
String query = "insert into positions (name, description) values (?, ?)";
try(PreparedStatement statement = connection.prepareStatement(query)) {
statement.setString(1, position.getName());
statement.setString(2, position.getDescription());
statement.executeUpdate();
}
connection.commit();
}
catch (SQLException e) {
e.printStackTrace();
connection.rollback();
}
finally {
connection.setAutoCommit(isAutoCommit);
}
}
The only way to go through is by directly executing the query with fixed values. But in doing so, I am forced to use a concatenation to build the query. And I do not want to do it.
try(Connection connection = getDataSource().getConnection()) {
boolean isAutoCommit = connection.getAutoCommit();
try {
connection.setAutoCommit(false);
try(Statement statement = connection.createStatement()) {
statement.execute("set local app.user_id to 0000");
}
String query = "insert into positions (name, description) values (?, ?)";
try(PreparedStatement statement = connection.prepareStatement(query)) {
statement.setString(1, position.getName());
statement.setString(2, position.getDescription());
statement.executeUpdate();
}
connection.commit();
}
catch (SQLException e) {
e.printStackTrace();
connection.rollback();
}
finally {
connection.setAutoCommit(isAutoCommit);
}
}
What is the right way to initialize such parameters?
I use PostgreSQL 11, JDBC 4.2 (with driver 42.2.5) and DBCP 2.5
Edit
I did it by calling set_config.
try(PreparedStatement statement = connection.prepareStatement("select set_config(?, ?, true)")) {
statement.setString(1, "app.user_id");
statement.setString(2, "0000");
statement.execute();
}
But the question remains. How to call SET in JDBC
I think you need to do this on the DataSource not the Connection.
In postgresql the only way I know of would be to downconvert. Something like:
DataSource myDS = getDataSource();
if (DataSource instanceof BaseDataSource.class) {
BaseDataSource pgDS = (BaseDataSource) myDS; // expose setProperty method
pgDS.setProperty("app.user_id", "0000");
}
where you place this in your application obviously depends upon many details not presented in your question.
I am trying to retrieve the value of a TEXT field from a table in a MySQL database.
MySQL version is 5.6.21
& I am using mysql-connector-java-5.1.18-bin.jar
My file is given below
import java.sql.*;
public class DatabaseConnection {
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/book";
// database credentials
static final String USER = "username";
static final String PASS = "password";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Creating statement...");
stmt = conn.createStatement();
String query;
query = "Select b_name, description columns from brands";
ResultSet rs = stmt.executeQuery(query);
while(rs.next()) {
String first_name = rs.getString("b_name");
String description = rs.getString("description");
System.out.println(first_name);
System.out.println(description);
}
rs.close();
stmt.close();
conn.close();
} catch(SQLException se) {
se.printStackTrace();
} catch(ClassNotFoundException cnfe) {
cnfe.printStackTrace();
}
finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
} catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
} catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}
}
This says that my column does not exist although I have tried this on another table, it works on VARCHAR columns but not on TEXT columns
This error shows up:
But the table has a column named description:
The problem is NOT about the column type being text.
You can get the value of a TEXT type using getString.
You can verify in the documentation.
The problem is in the query:
query = "Select b_name, description columns from brands";
"columns" there is a mistake.
Written this way, the description column is in fact renamed to columns in your result set.
If you did rs.getString("columns") you would get the value.
But that's not what you want to do. You want to fix the query by dropping that word:
query = "Select b_name, description from brands";
public static void main(String[] argv) {
try {
createTable();
insertRecordIntoTable("leo","123");
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
private static void createTable() throws SQLException {
Connection dbConnection = null;
PreparedStatement preparedStatement = null;
String sequence = "CREATE SEQUENCE ID_SEQ INCREMENT BY 1 MAXVALUE 99999999999999999999 MINVALUE 1 CACHE 20";
String createTableSQL = "CREATE TABLE DBUSER1("
+ "USER_ID NUMBER(5) NOT NULL, "
+ "USERNAME VARCHAR(20) NOT NULL, "
+ "PASSWORD VARCHAR(20) NOT NULL, "
+ "PRIMARY KEY (USER_ID) "
+ ")";
try {
dbConnection = getDBConnection();
preparedStatement = dbConnection.prepareStatement(createTableSQL);
System.out.println(createTableSQL);
// execute create SQL stetement
preparedStatement.executeUpdate(createTableSQL);
preparedStatement.executeUpdate(sequence);
System.out.println("Table \"dbuser\" is created!");
} catch (SQLException e) {
System.out.println(e.getMessage());
} finally {
if (preparedStatement != null) {
preparedStatement.close();
}
if (dbConnection != null) {
dbConnection.close();
}
}
}
private static Connection getDBConnection() {
Connection dbConnection = null;
try {
Class.forName(DB_DRIVER);
} catch (ClassNotFoundException e) {
System.out.println(e.getMessage());
}
try {
dbConnection = DriverManager.getConnection(
DB_CONNECTION, DB_USER,DB_PASSWORD);
return dbConnection;
} catch (SQLException e) {
System.out.println(e.getMessage());
}
return dbConnection;
}
private static void insertRecordIntoTable(String username, String password) throws SQLException {
Connection dbConnection = null;
PreparedStatement preparedStatement = null;
String insertTableSQL = "INSERT INTO DBUSER1"
+ "(USER_ID, USERNAME, PASSWORD) VALUES"
+ "(ID_SEQ.NEXTVAL,?,?)";
try {
dbConnection = getDBConnection();
preparedStatement = dbConnection.prepareStatement(insertTableSQL);
// execute insert SQL stetement
preparedStatement.setString(1, username);
preparedStatement.setString(2, password);
preparedStatement.executeUpdate();
System.out.println("Record is inserted into DBUSER table!");
} catch (SQLException e) {
System.out.println(e.getMessage());
} finally {
if (preparedStatement != null) {
preparedStatement.close();
}
if (dbConnection != null) {
dbConnection.close();
}
}
}
I cannot find the error when I try to create a sequence for my table.
When I try to insert some data in my table with the sequence it says it doesn't exist, but I did create it. Also I am not sure if i need a preparedStatement.setInt(1, seq_id.nextval); it gives an error but im not quite sure how I would do this
The solution might be adding the schema name (owner) before the name of sequence:
CREATE SEQUENCE some_nameOf_schema.ID_SEQ INCREMENT BY 1 MAXVALUE 99999999999999999999 MINVALUE 1 CACHE 20
You're preparing a statement with one SQL text, and executing the statement with two different SQL texts;
preparedStatement = dbConnection.prepareStatement(createTableSQL);
preparedStatement.executeUpdate(createTableSQL);
preparedStatement.executeUpdate(sequence);
...which is actually invalid according to the docs;
int executeUpdate(String sql)
throws SQLException
Executes the given SQL statement, which may be an INSERT, UPDATE, or DELETE statement or an SQL statement that returns nothing, such as an SQL DDL statement.
Note:This method cannot be called on a PreparedStatement or CallableStatement.
What you need to do is to prepare and execute two different statements;
preparedStatement = dbConnection.prepareStatement(createTableSQL);
preparedStatement.executeUpdate();
preparedStatement = dbConnection.prepareStatement(sequence);
preparedStatement.executeUpdate();
In general, it doesn't make much sense to CREATE database objects every time your application starts up, because this is something that's usually done only once, when you install/upgrade the database/schema the application uses.
However, if you really have to do it this way, the current solution could be improved so that the following points are considered:
Only execute the CREATE statements when the objects do not yet exist in the DB. This can be done by first inspecting the USER_OBJECTS data dictionary view.
Use a plain Statement instead of PreparedStatement for executing the DDL (prepared statements are only useful for DML operations that use input variables)
Handle JDBC resources (Connection / Statement / ResultSet) concisely and safely through the try-with-resources construct
Here's how the code could look like:
// query constants
private static final String CHECK_DB_OBJECT =
"SELECT 1 FROM user_objects WHERE object_name = ?";
private static final String CREATE_SEQUENCE =
"CREATE SEQUENCE ID_SEQ INCREMENT BY 1 MAXVALUE 99999999999999999999" +
" MINVALUE 1 CACHE 20";
private static final String CREATE_TABLE = "CREATE TABLE DBUSER1("
+ "USER_ID NUMBER(5) NOT NULL, "
+ "USERNAME VARCHAR(20) NOT NULL, "
+ "PASSWORD VARCHAR(20) NOT NULL, "
+ "PRIMARY KEY (USER_ID) "
+ ")";
/* clip the main method etc. */
/**
* Creates the table and sequence only if they do not already exist.
*/
private static void createTableAndSequenceIfAbsent() {
try (Connection dbConnection = DriverManager.getConnection(
DB_CONNECTION, DB_USER, DB_PASSWORD);
PreparedStatement ps = dbConnection
.prepareStatement(CHECK_DB_OBJECT)) {
if (!dbObjectExists(ps, "ID_SEQ")) {
executeDDL(dbConnection, CREATE_SEQUENCE);
}
if (!dbObjectExists(ps, "DBUSER1")) {
executeDDL(dbConnection, CREATE_TABLE);
}
} catch (SQLException e) {
e.printStackTrace();
}
}
private static boolean dbObjectExists(PreparedStatement ps,
String objectName) throws SQLException {
ps.setString(1, objectName);
ResultSet rs = ps.executeQuery();
// if the #CHECK_DB_OBJECT query returned a row, the object exists
return rs.next();
}
private static void executeDDL(Connection c, String sql)
throws SQLException {
try (Statement st = c.createStatement()) {
st.execute(sql);
}
}
I have a problem inserting data into MYSQL database. Using code below I get an error:
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?,?)' at line 1
CODE:
public void signUpUser(Connection conn, String userName, String password) {
String queryString = "INSERT INTO USERS (USER_ALIAS, USER_PASS) VALUES (?,?)";
try {
preparedStatement = (PreparedStatement) conn.prepareStatement(queryString);
preparedStatement.setString(1, userName);
preparedStatement.setString(2, password);
preparedStatement.executeUpdate(queryString);
} catch (SQLException e) {
e.printStackTrace();
}
}
But with this code the insert works normally:
public void signUpUser(Connection conn, String userName, String password) {
String queryString = "INSERT INTO USERS (USER_ALIAS, USER_PASS) VALUES ('"+userName+"', '"+password+"')";
try {
preparedStatement = (PreparedStatement) conn.prepareStatement(queryString);
preparedStatement.executeUpdate(queryString);
} catch (SQLException e) {
e.printStackTrace();
}
}
I want to know why does it throws error while using first part of code
Thank you in advance!
You are trying to execute update with the string although you have already created the statement.
You have to use:
preparedStatement.executeUpdate();
I have a problem trying to execute more than one query into my Java Application code.
I have a procedure that is called in main and is in the class "Fant":
public void XXX(){
Connectivity con=new Connectivity(); // this class set up the data for the connection to db; if ( !con.connect() ) {
System.out.println("Error during connection.");
System.out.println( con.getError() );
System.exit(0);
}
ArrayList<User> blabla=new ArrayList<User>();
blabla=this.getAllUsers(con);
for (User u:blabla)
{
try {
Connectivity coni=new Connectivity();//start a new connection each time that i perform a query
Statement t;
t = coni.getDb().createStatement();
String query = "Select count(*) as rowcount from berebe.baraba";
ResultSet rs = t.executeQuery(query);
int numPrenotazioni=rs.getInt("rowcount");
rs.close(); //close resultset
t.close(); //close statement
coni.getDb().close(); //close connection
}
}
catch (SQLException e)
{
System.err.println("SQLState: " +
((SQLException)e).getSQLState());
System.err.println("Error Code: " +
((SQLException)e).getErrorCode());
}
}
}
The called function is defined as:
ArrayList<User> getAllUsers(Connectivity con) {
try{
ArrayList<User> userArrayList=new ArrayList<User>();
String query = "Select idUser,bubu,lala,sisi,gogo,gg from berebe.sasasa";
Statement t;
t = con.getDb().createStatement();
ResultSet rs = t.executeQuery(query);
while (rs.next())
{
User utente=new User(....); //user fields got from query
userArrayList.add(utente);
}
rs.close();
t.close();
con.disconnect(); //disconnect the connection
return userArrayList;
} catch (SQLException e) {
}
return null;
}
The main is:
public static void main(String[] argv) {
ArrayList<User> users=new ArrayList<User>();
System.out.println("-------- MySQL JDBC Connection Testing ------------");
Fant style = new Fant();
style.XXX();
}
The query performed into "getAllusers" is executed and into the arraylist "blabla" there are several users; the problem is that the second query that needs the count is never executed.
The MYSQlState given when running is= "S1000" and the SQLERROR is "0".
Probably i'm mistaking on connections issues but i'm not familiar with statements,connections,resultsets.
Thank you.
You might forget to call rs.next() before getting the result form it in XXX()methods as shown below:
ResultSet rs = t.executeQuery(query);
// call rs.next() first here
int numPrenotazioni=rs.getInt("rowcount");