try{
Connection conn = getConnection();
String strUpdateQuery = "update payment_table set CREDIT_CARD_NO = ? where PAYMENT_KEY= ?";
PreparedStatement ps =conn.prepareStatement(strUpdateQuery);
for(int i=0;i<nodes.getLength();i++){
ps.setString(1,"524364OQNBQQ4291");
ps.setString(2,"20130215123757533280168");
ps.executeUpdate();
conn.commit();
}
}catch(SQLException e){
e.printStackTrace();
}
Not updating even a single row even after I checked the primary key is correct.
Try with batch update:
void batchUpdate() {
String strUpdateQuery = "UPDATE payment_table " +
"SET CREDIT_CARD_NO = ? " +
"WHERE PAYMENT_KEY= ?";
try (Connection conn = getConnection();
PreparedStatement ps = conn.prepareStatement(strUpdateQuery)) {
for (int i = 0; i < nodes.getLength(); i++) {
ps.setString(1, "524364OQNBQQ4291");
ps.setString(2, "20130215123757533280168");
ps.addBatch();
}
int[] updated = ps.executeBatch();
// can log updated rows from "updated"
// conn.commit(); in case autocommit set to false or used conn.setAutoCommit(false) somewhere
}
catch (SQLException e) {
e.printStackTrace();
}
}
ps.setXxx(): You can check the order. The sequence must be the same as the column names in the result level returned by the resultSet!!
Related
I want to update about 10K records into MySQL DB in less than a second. I have written below code which takes about 6-8 seconds to update a list of records into DB.
public void updateResultList(List<?> list) {
String user = "root";
String pass = "root";
String jdbcUrl = "jdbc:mysql://12.1.1.1/db_1?useSSL=false";
String driver = "com.mysql.jdbc.Driver";
PreparedStatement pstm = null;
try {
Class.forName(driver);
Connection myConn = DriverManager.getConnection(jdbcUrl, user, pass);
myConn.setAutoCommit(false);
for(int i=0; i<list.size(); i++) {
Object[] row = (Object[]) list.get(i);
int candidateID = Integer.valueOf(String.valueOf(row[0]));
String result = String.valueOf(row[14]);
int score = Integer.valueOf(String.valueOf(row[19]));
String uploadState = (String) row[20];
String sql = "UPDATE personal_info SET result = ?, score = ?, uploadState = ? "
+ " WHERE CandidateID = ?";
pstm = (PreparedStatement) myConn.prepareStatement(sql);
pstm.setString(1, result);
pstm.setInt(2, score);
pstm.setString(3, uploadState);
pstm.setInt(4, candidateID);
pstm.addBatch();
pstm.executeBatch();
}
myConn.commit();
myConn.setAutoCommit(true);
pstm.close();
myConn.close();
}
catch (Exception exc) {
exc.printStackTrace();
try {
throw new ServletException(exc);
} catch (ServletException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Please let me know your inputs to optimize this code for performance improvement.
First, you need to init prepareStatement only once,you need to init it before the for loop
Second,you should avoid excute pstm.executeBatch(); for every loop it will cost much more resource,you need to execute it for a specified amount,such as 100,500 or more,also do not execute it outside the for loop for only once,due to it will cost more memory resource
Class.forName(driver);
Connection myConn = DriverManager.getConnection(jdbcUrl, user, pass);
myConn.setAutoCommit(false);
String sql = "UPDATE personal_info SET result = ?, score = ?, uploadState = ? "
+ " WHERE CandidateID = ?";
pstm = (PreparedStatement) myConn.prepareStatement(sql);
for(int i=0; i<list.size(); i++) {
Object[] row = (Object[]) list.get(i);
int candidateID = Integer.valueOf(String.valueOf(row[0]));
String result = String.valueOf(row[14]);
int score = Integer.valueOf(String.valueOf(row[19]));
String uploadState = (String) row[20];
pstm.setString(1, result);
pstm.setInt(2, score);
pstm.setString(3, uploadState);
pstm.setInt(4, candidateID);
pstm.addBatch();
if(i%500==0){//execute when it meet a specified amount
pstm.executeBatch();
}
}
pstm.executeBatch();
myConn.commit();
myConn.setAutoCommit(true);
Rather than batching the individual UPDATEs, you could batch INSERTs into a temporary table with rewriteBatchedStatements=true and then use a single UPDATE statement to update the main table. On my machine with a local MySQL instance, the following code takes about 2.5 seconds ...
long t0 = System.nanoTime();
conn.setAutoCommit(false);
String sql = null;
sql = "UPDATE personal_info SET result=?, score=?, uploadState=? WHERE CandidateID=?";
PreparedStatement ps = conn.prepareStatement(sql);
String tag = "X";
for (int i = 1; i <= 10000; i++) {
ps.setString(1, String.format("result_%s_%d", tag, i));
ps.setInt(2, 200000 + i);
ps.setString(3, String.format("state_%s_%d", tag, i));
ps.setInt(4, i);
ps.addBatch();
}
ps.executeBatch();
conn.commit();
System.out.printf("%d ms%n", (System.nanoTime() - t0) / 1000000);
... while this version takes about 1.3 seconds:
long t0 = System.nanoTime();
conn.setAutoCommit(false);
String sql = null;
Statement st = conn.createStatement();
st.execute("CREATE TEMPORARY TABLE tmp (CandidateID INT, result VARCHAR(255), score INT, uploadState VARCHAR(255))");
sql = "INSERT INTO tmp (result, score, uploadState, CandidateID) VALUES (?,?,?,?)";
PreparedStatement ps = conn.prepareStatement(sql);
String tag = "Y";
for (int i = 1; i <= 10000; i++) {
ps.setString(1, String.format("result_%s_%d", tag, i));
ps.setInt(2, 400000 + i);
ps.setString(3, String.format("state_%s_%d", tag, i));
ps.setInt(4, i);
ps.addBatch();
}
ps.executeBatch();
sql =
"UPDATE personal_info pi INNER JOIN tmp ON tmp.CandidateID=pi.CandidateID "
+ "SET pi.result=tmp.result, pi.score=tmp.score, pi.uploadState=tmp.uploadState";
st.execute(sql);
conn.commit();
System.out.printf("%d ms%n", (System.nanoTime() - t0) / 1000000);
your pstm.executeBatch() should be after forloop
refer How to insert List into database
I have a problem with line pstmt.setLong(1, id);. I get an error that the value is not set for the parameter number 1. If I use the String SQL without the question mark, it works. Also, when I use ARM the PreparedStatement and ResultSet are not automatically closed so I have to close them, and finally doesn't seem to work either
#Override
public Company getCompany(long id) {
Connection con = ConnectionPool.getInstance().getConnection();
String sql = "SELECT * FROM Company WHERE ID=?";
//String sql = "SELECT * FROM Company WHERE ID=" + id;
Company company = new Company();
try (
PreparedStatement pstmt = con.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();)
{
pstmt.setLong(1, id);
if (rs.next()) {
company.setId(rs.getLong(1));
company.setCompName(rs.getString(2));
company.setPassword(rs.getString(3));
company.setEmail(rs.getString(4));
} else {
System.out.println("Company with ID: " + id + " could not be found\n");
}
pstmt.close();
rs.close();
} catch (SQLException e) {
CouponSystemException ex = new CouponSystemException("Company with ID: " + id + " could not be retrieved\n", e);
System.out.println(ex.getMessage());
System.out.println(e);
}
ConnectionPool.getInstance().returnConnection(con);
return company;
}
Set the parameter before executing the query.
Also, You don't need to close Statement and result sets defined in try-with-resource statements as they'll be closed automatically when you leave the try scope.
try(PreparedStatement pstmt = con.prepareStatement(sql)) {
pstmt.setLong(1, id);
try(ResultSet rs = pstmt.executeQuery()) {
// do stuff
}
}
You need to set the PreparedStatement's parameters before executing it. Also note that this you're using the try-with-resource syntax you shouldn't close the resources yourself:
try (PreparedStatement pstmt = con.prepareStatement(sql)) {
pstmt.setLong(1, id);
try (ResultSet rs = pstmt.executeQuery()) {
if (rs.next()) {
company.setId(rs.getLong(1));
company.setCompName(rs.getString(2));
company.setPassword(rs.getString(3));
company.setEmail(rs.getString(4));
} else {
System.out.println("Company with ID: " + id + " could not be found\n");
}
}
} catch (SQLException e) {
CouponSystemException ex = new CouponSystemException("Company with ID: " + id + " could not be retrieved\n", e);
System.out.println(ex.getMessage());
System.out.println(e);
}
I am writing a program that will take in a student ID and verify if that ID exists in a mysql table. If it does exist, I would like to take the entire row that it exists in and copy that row to another table. Currently the program will just copy all rows in a table to the other. Any help appreciated. I have inserted a snippet of code below.
try {
String compareText = IDField.getText().trim();
if(compareText.length() > 0){
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/simlab","root","password");
System.out.println("Connected to database");
Statement stmt1 = conn.createStatement();
ResultSet rs1 = stmt1.executeQuery("select * from students where LUID='"+IDField.getText()+"' ");
boolean isPresent = rs1.next();
if (isPresent)
{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/simlab","root","password");
System.out.println("Connected to database");
int rows = stmt1.executeUpdate("INSERT INTO skills(ID_Student,LUID_Student)SELECT ID, LUID FROM students");
if (rows == 0)
{
System.out.println("Don't add any row!");
}
else
{
System.out.println(rows + " row(s)affected.");
conn.close();
}
//System.out.println("Already exists!!");
}
You could all do that in a single SQL statement:
INSERT INTO <Dest-Table>
(SELECT * FROM <Src-Table> WHERE ID=?);
It will only copy rows that exist.
I suspect it's due to this line:
int rows = stmt1.executeUpdate("INSERT INTO skills(ID_Student,LUID_Student)SELECT ID, LUID FROM students");
As, if that line is parsed, the SELECT statement has no WHERE clause, and will therefore get every row, and therefore insert everything.
With Prepared statements
String sql = "INSERT INTO abc"
+ "(SELECT id1,id2 FROM pqr)";
ps1 = con.prepareStatement(sql);
int rs = ps1.executeUpdate();
if (rs > 0) {
update = true;
} else {
update = false;
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
if (ps1 != null) {
ps1.close();
ps1 = null;
}
if (con != null) {
con.close();
con = null;
}
} catch (Exception e) {
}
}
return update;
Can we use two queries in one method while using prepared statement, I have tried using this but invalid column name exception is coming.
My code snippets is as follows.
public double getPayroll(){
ResultSet rs = null;
ResultSet rs2 = null;
Connection conn = null;
PreparedStatement pstmt = null;
try {
conn = getDBConnection();
int employeeId;
String q1 = "select e_salary,e_house_rent,e_conv_allow,e_id
from employee";
pstmt = conn.prepareStatement(q1);
rs = pstmt.executeQuery();
double dailyPay=0,basicPay=0,payroll2=0;
int houseRent=0,convAllow=0;
while (rs.next()) {
dailyPay = rs.getInt(1)*.03;
houseRent=rs.getInt(2);
convAllow=rs.getInt(3);
employeeId=rs.getInt(4);
}
String q2="select att_status from attendance where
e_id=employeeId";
pstmt = conn.prepareStatement(q2);
rs2 = pstmt.executeQuery();
int noOfPresents = 0;
while(rs2.next()){
noOfPresents+=1;
}
basicPay=dailyPay*noOfPresents;
payroll2+=basicPay+houseRent+convAllow;
return payroll2;
} catch (Exception e) {
e.printStackTrace();
return 0.0;
} finally {
try {
rs.close();
pstmt.close();
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
Your problem is that the sql in q2 assumes that there is a column named employeeId, but I suspect you want to insert the value of the variable employeeId.
Change it to
select att_status from attendance where e_id=?
Then execute
pstmt.setString(1, employeeId);
before executing pstmt.executeQuery();
With java.sql.ResultSet is there a way to get a column's name as a String by using the column's index? I had a look through the API doc but I can't find anything.
You can get this info from the ResultSet metadata. See ResultSetMetaData
e.g.
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
String name = rsmd.getColumnName(1);
and you can get the column name from there. If you do
select x as y from table
then rsmd.getColumnLabel() will get you the retrieved label name too.
In addition to the above answers, if you're working with a dynamic query and you want the column names but do not know how many columns there are, you can use the ResultSetMetaData object to get the number of columns first and then cycle through them.
Amending Brian's code:
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int columnCount = rsmd.getColumnCount();
// The column count starts from 1
for (int i = 1; i <= columnCount; i++ ) {
String name = rsmd.getColumnName(i);
// Do stuff with name
}
You can use the the ResultSetMetaData (http://java.sun.com/javase/6/docs/api/java/sql/ResultSetMetaData.html) object for that, like this:
ResultSet rs = stmt.executeQuery("SELECT * FROM table");
ResultSetMetaData rsmd = rs.getMetaData();
String firstColumnName = rsmd.getColumnName(1);
This question is old and so are the correct previous answers. But what I was looking for when I found this topic was something like this solution. Hopefully it helps someone.
// Loading required libraries
import java.util.*;
import java.sql.*;
public class MySQLExample {
public void run(String sql) {
// JDBC driver name and database URL
String JDBC_DRIVER = "com.mysql.jdbc.Driver";
String DB_URL = "jdbc:mysql://localhost/demo";
// Database credentials
String USER = "someuser"; // Fake of course.
String PASS = "somepass"; // This too!
Statement stmt = null;
ResultSet rs = null;
Connection conn = null;
Vector<String> columnNames = new Vector<String>();
try {
// Register JDBC driver
Class.forName(JDBC_DRIVER);
// Open a connection
conn = DriverManager.getConnection(DB_URL, USER, PASS);
// Execute SQL query
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
if (rs != null) {
ResultSetMetaData columns = rs.getMetaData();
int i = 0;
while (i < columns.getColumnCount()) {
i++;
System.out.print(columns.getColumnName(i) + "\t");
columnNames.add(columns.getColumnName(i));
}
System.out.print("\n");
while (rs.next()) {
for (i = 0; i < columnNames.size(); i++) {
System.out.print(rs.getString(columnNames.get(i))
+ "\t");
}
System.out.print("\n");
}
}
} catch (Exception e) {
System.out.println("Exception: " + e.toString());
}
finally {
try {
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (conn != null) {
conn.close();
}
} catch (Exception mysqlEx) {
System.out.println(mysqlEx.toString());
}
}
}
}
SQLite 3
Using getMetaData();
DatabaseMetaData md = conn.getMetaData();
ResultSet rset = md.getColumns(null, null, "your_table_name", null);
System.out.println("your_table_name");
while (rset.next())
{
System.out.println("\t" + rset.getString(4));
}
EDIT: This works with PostgreSQL as well
import java.sql.*;
public class JdbcGetColumnNames {
public static void main(String args[]) {
Connection con = null;
Statement st = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/komal", "root", "root");
st = con.createStatement();
String sql = "select * from person";
rs = st.executeQuery(sql);
ResultSetMetaData metaData = rs.getMetaData();
int rowCount = metaData.getColumnCount();
System.out.println("Table Name : " + metaData.getTableName(2));
System.out.println("Field \tDataType");
for (int i = 0; i < rowCount; i++) {
System.out.print(metaData.getColumnName(i + 1) + " \t");
System.out.println(metaData.getColumnTypeName(i + 1));
}
} catch (Exception e) {
System.out.println(e);
}
}
}
Table Name : person
Field DataType
id VARCHAR
cname VARCHAR
dob DATE
while (rs.next()) {
for (int j = 1; j < columncount; j++) {
System.out.println( rsd.getColumnName(j) + "::" + rs.getString(j));
}
}
When you need the column names, but do not want to grab entries:
PreparedStatement stmt = connection.prepareStatement("SHOW COLUMNS FROM `yourTable`");
ResultSet set = stmt.executeQuery();
//store all of the columns names
List<String> names = new ArrayList<>();
while (set.next()) { names.add(set.getString("Field")); }
NOTE: Only works with MySQL
The SQL statements that read data from a database query return the data in a result set. The SELECT statement is the standard way to select rows from a database and view them in a result set. The **java.sql.ResultSet** interface represents the result set of a database query.
Get methods: used to view the data in the columns of the current row
being pointed to by the cursor.
Using MetaData of a result set to fetch the exact column count
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int numberOfColumns = rsmd.getColumnCount();
boolean b = rsmd.isSearchable(1);
http://docs.oracle.com/javase/7/docs/api/java/sql/ResultSetMetaData.html
and further more to bind it to data model table
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Connected database successfully...");
//STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
String sql = "SELECT id, first, last, age FROM Registration";
ResultSet rs = stmt.executeQuery(sql);
//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
rs.close();
} catch(SQLException se) {
//Handle errors for JDBC
se.printStackTrace();
} catch(Exception e) {
//Handle errors for Class.forName
e.printStackTrace();
} finally {
//finally block used to close resources
try {
if(stmt!=null)
conn.close();
} catch(SQLException se) {
} // do nothing
try {
if(conn!=null)
conn.close();
} catch(SQLException se) {
se.printStackTrace();
} //end finally try
}//end try
System.out.println("Goodbye!");
}//end main
//end JDBCExample
very nice tutorial here : http://www.tutorialspoint.com/jdbc/
ResultSetMetaData meta = resultset.getMetaData(); // for a valid resultset object after executing query
Integer columncount = meta.getColumnCount();
int count = 1 ; // start counting from 1 always
String[] columnNames = null;
while(columncount <=count) {
columnNames [i] = meta.getColumnName(i);
}
System.out.println (columnNames.size() ); //see the list and bind it to TableModel object. the to your jtbale.setModel(your_table_model);
#Cyntech is right.
Incase your table is empty and you still need to get table column names you can get your column as type Vector,see the following:
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int columnCount = rsmd.getColumnCount();
Vector<Vector<String>>tableVector = new Vector<Vector<String>>();
boolean isTableEmpty = true;
int col = 0;
while(rs.next())
{
isTableEmpty = false; //set to false since rs.next has data: this means the table is not empty
if(col != columnCount)
{
for(int x = 1;x <= columnCount;x++){
Vector<String> tFields = new Vector<String>();
tFields.add(rsmd.getColumnName(x).toString());
tableVector.add(tFields);
}
col = columnCount;
}
}
//if table is empty then get column names only
if(isTableEmpty){
for(int x=1;x<=colCount;x++){
Vector<String> tFields = new Vector<String>();
tFields.add(rsmd.getColumnName(x).toString());
tableVector.add(tFields);
}
}
rs.close();
stmt.close();
return tableVector;
ResultSet rsTst = hiSession.connection().prepareStatement(queryStr).executeQuery();
ResultSetMetaData meta = rsTst.getMetaData();
int columnCount = meta.getColumnCount();
// The column count starts from 1
String nameValuePair = "";
while (rsTst.next()) {
for (int i = 1; i < columnCount + 1; i++ ) {
String name = meta.getColumnName(i);
// Do stuff with name
String value = rsTst.getString(i); //.getObject(1);
nameValuePair = nameValuePair + name + "=" +value + ",";
//nameValuePair = nameValuePair + ", ";
}
nameValuePair = nameValuePair+"||" + "\t";
}
If you want to use spring jdbctemplate and don't want to deal with connection staff, you can use following:
jdbcTemplate.query("select * from books", new RowCallbackHandler() {
public void processRow(ResultSet resultSet) throws SQLException {
ResultSetMetaData rsmd = resultSet.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); i++ ) {
String name = rsmd.getColumnName(i);
// Do stuff with name
}
}
});
U can get column name and value from resultSet.getMetaData();
This code work for me:
Connection conn = null;
PreparedStatement preparedStatement = null;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
conn = MySQLJDBCUtil.getConnection();
preparedStatement = conn.prepareStatement(sql);
if (params != null) {
for (int i = 0; i < params.size(); i++) {
preparedStatement.setObject(i + 1, params.get(i).getSqlValue());
}
ResultSet resultSet = preparedStatement.executeQuery();
ResultSetMetaData md = resultSet.getMetaData();
while (resultSet.next()) {
int counter = md.getColumnCount();
String colName[] = new String[counter];
Map<String, Object> field = new HashMap<>();
for (int loop = 1; loop <= counter; loop++) {
int index = loop - 1;
colName[index] = md.getColumnLabel(loop);
field.put(colName[index], resultSet.getObject(colName[index]));
}
rows.add(field);
}
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (preparedStatement != null) {
try {
preparedStatement.close();
}catch (Exception e1) {
e1.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
return rows;
I know, this question is already answered but probably somebody like me needs to access a column name from DatabaseMetaData by label instead of index:
ResultSet resultSet = null;
DatabaseMetaData metaData = null;
try {
metaData = connection.getMetaData();
resultSet = metaData.getColumns(null, null, tableName, null);
while (resultSet.next()){
String name = resultSet.getString("COLUMN_NAME");
}
}