im trying to update a column using jsp
here i want my count column value to be updated as zero
count = 0
how can i do that. through this code value is not updating
String code = request.getParameter("code");
Connection conn = null;
Statement st=null;
ResultSet rs = null;
PreparedStatement ps = null;
int count = 0;
try{
conn = DataBaseConnection.initializeDatabase();
String query1 = null;
conn.setAutoCommit(false);
query1 = "update employee set count = ? where code= ' +code+' ";
ps = conn.prepareStatement(query1);
ps.setInt(1, count);
ps.executeUpdate();
}
catch (Exception e) {
e.printStackTrace();
}
here is my record in db
employee table
CODE VARCHAR2(12)
COUNT NUMBER(3)
You can replace
"update employee set count = ? where code= ' +code+' ";
with
"update employee set count = ? where code= '" + code + "'";
e.g. if the value of code is xyz then after this change, the query will become:
"update employee set count = ? where code= 'xyz'";
However, I recommend you do it as follows to avoid the SQL Injection:
query1 = "update employee set count = ? where code= ?";
ps = conn.prepareStatement(query1);
ps.setInt(1, count);
ps.setString(2, code);
Related
I am trying to update a database using input from user and saving it in jtable, then using jtable I am updating the database, but I am not able to get fetch and update 2nd row in database.
please suggest a solution, Thanks in advance.
try {
Class.forName("com.mysql.jdbc.Driver");
con = myconnection.getConnection();
String name;
for (int i = 0; i < jTable2.getRowCount(); i++) {
name = (String) jTable2.getModel().getValueAt(i, 0);
String abcd = "select * from medicine where Name=? ";
stmt = conn.prepareStatement(abcd);
stmt.setString(1, name);
rs = stmt.executeQuery();
if (rs.next()) {
name = (String) jTable2.getModel().getValueAt(i, 0);
String stock = rs.getString("qty");
int nowstock = Integer.parseInt(stock);
int qty1 = Integer.parseInt(jTable2.getValueAt(i, 2).toString());
int newstock = nowstock - qty1;//Integer.parseInt(jTable2.getValueAt(i, 2).toString());
String sqlupdate = "UPDATE medicine SET qty='" + newstock + "'WHERE Name='" + name + "' "; //
stmt = conn.prepareStatement(sqlupdate);
stmt.executeUpdate();
}
}
} catch (ClassNotFoundException ex) {
Logger.getLogger(Bill.class.getName()).log(Level.SEVERE, null, ex);
} catch (SQLException ex) {
Logger.getLogger(Bill.class.getName()).log(Level.SEVERE, null, ex);
}
The select serves no purpose, and you can just iterate all names and update directly:
for (int i=0; i < jTable2.getRowCount(); i++) {
String name = (String) jTable2.getModel().getValueAt(i, 0);
int qty1 = Integer.parseInt(jTable2.getValueAt(i, 2).toString());
String update = "UPDATE medicine SET qty = qty - ? WHERE Name = ?";
PreparedStatement ps = conn.prepareStatement(update);
ps.setInt(1, qty1);
ps.setString(2, name);
ps.executeUpdate();
}
If your JTable happens to have more than say 10 or so names, then a more efficient way to do this would be to use a single update with a WHERE IN clause containing all names which appear in the table, i.e.
UPDATE medicine SET qty = qty - ? WHERE Name IN (...);
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 problem with SQL query in JAVA.
JAVA code:
public boolean zeKontrolaExistujiciZalohyTest(String datum) {
try {
connected();
boolean existujeZaloha = false;
int pocet;
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('"+datum+"', 'dd.mm.yyyy'), 'mm.yyyy')");
rs.next();
pocet = rs.getInt(1);
rs.close();
closed();
if (pocet >= 0) {
existujeZaloha = true;
} else {
existujeZaloha = false;
}
return existujeZaloha;
} catch (Exception e) {
e.printStackTrace();
Dialogs.create()
.title("Exception Dialog")
.showException(e);
return true;
}
}
SQL query in SQL Developer:
SELECT count(id) FROM pbtest.u_zalohy_energie
WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('15.09.2014', 'dd.mm.yyyy'), 'mm.yyyy');
When I run JAVA code, so result a variable is "pocet = 0". But, when I run SQL query in any the SQL Developer, so result column COUNT(id) is "1".
When I do change the SQL query, let me run JAVA code retuns a variable "pocet = 1".
Change sql code:
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE datum = TO_DATE('"+datum+"', 'dd.mm.yyyy')");
Does anyone know where is the problem?
For information: I use an Oracle database.
Thank you.
datum is string
SELECT count(id)
FROM pbtest.u_zalohy_energie
WHERE TO_DATE(datum, 'dd.mm.yyyy') = TO_DATE('15.09.2014', 'dd.mm.yyyy');
datum is date
SELECT count(id)
FROM pbtest.u_zalohy_energie
WHERE TRUNC(datum) = TO_DATE('15.09.2014', 'dd.mm.yyyy');
If datum is date, it might contain time component too. So remove it. using TRUNC()
TRUNC(datum) = TO_DATE('15.09.2014', 'dd.mm.yyyy');
Java code:
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE TRUNC(datum) = TO_DATE('"+datum+"', 'dd.mm.yyyy')");
As a side note, use PreparedStatement and bind variables to avoid SQL*Injection
Your statement has a syntax error
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('"+datum+"', 'dd.mm.yyyy'), 'mm.yyyy')");
the executed query would be
SELECT count(id) FROM pbtest.u_zalohy_energie\nWHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('15.09.2014'', 'dd.mm.yyyy'), 'mm.yyyy')")
You should remove the "\n" as this will not lead in a line break.
Try it as
ResultSet rs = statement.executeQuery("SELECT count(id) FROM " + table_ze
+ " WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('"+datum+"', 'dd.mm.yyyy'), 'mm.yyyy')");
Take also into consideration the comment from Maheswaran Ravisankar about: "... PreparedStatement and bind variables to avoid SQL*Injection"
Thank you for your advice, I solved the problem as follows:
public boolean zeKontrolaExistujiciZalohy(String datum, String typZalohy, String zalohaNaMesic) {
connected();
boolean existujeZaloha = false;
int pocet = 0;
ResultSet rs;
PreparedStatement pstmt = null;
try{
statement = connection.createStatement();
String SQL = "SELECT count(id) AS pocet FROM " + table_ze + " WHERE (EXTRACT(MONTH FROM datum)) = (EXTRACT(MONTH FROM to_date(?, 'dd.mm.yyyy'))) "
+ "AND (EXTRACT(YEAR FROM datum)) = (EXTRACT(YEAR FROM to_date(?, 'dd.mm.yyyy')))"
+ "AND typ_zalohy = ? "
+ "AND zaloha_na_mesic = ? ";
pstmt = connection.prepareStatement(SQL);
pstmt.setString(1, datum);
pstmt.setString(2, datum);
pstmt.setString(3, typZalohy);
pstmt.setString(4, zalohaNaMesic);
rs = pstmt.executeQuery();
while(rs.next()){
pocet = rs.getInt("pocet");
}
rs.close();
if (pocet > 0) {
existujeZaloha = true;
} else {
existujeZaloha = false;
}
return existujeZaloha;
}
catch(SQLException ex){
Dialogs.create()
.title("Exception Dialog")
.showException(ex);
return true;
}
}
I am trying to get the number of the affected records of this query SELECT mac, stop_name from behaviour where mac = ? with the use of the executeQuery. How can I get the number of the affected rows?
Code:
if (behaviourExist.next()) {
PreparedStatement prepared = con
.prepareStatement("SELECT mac, stop_name from behaviour where mac = ?");
prepared.setString(1, macD);
ResultSet rsBehav = prepared.executeQuery();
ArrayList<String> stopNameList = new ArrayList<String>();
while (rsBehav.next()) {
//int numberOfRows = rsBehav.getInt(1);
String stNa = rsBehav.getString("stop_name");
if (stNa.equals(nameShortestDistance)) {
stopNameList.add(stNa);
}
}
}
This is a read operation so it will not affect any row. If you want to get the number of row returned then you could do one of the below
Use a counter variable and increment it in the loop while (rsBehav.next())
Use a scrollable resultset
PreparedStatement prepared = con.prepareStatement(
"SELECT mac, stop_name from behaviour where mac = ?",
ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet rsBehav = prepared.executeQuery();
rsBehav.afterLast();
int numRow = rsBehav.getRow();
rsBehav.beforeFirst();
Here numRow will give you number or row returned,
PreparedStatement prepared = con
.prepareStatement(
"SELECT (SELECT count(*) from where mac = ?),"
" mac, stop_name from behaviour where mac = ?");
prepared.setString(1, macD);
prepared.setString(2, macD);
ResultSet rsBehav = prepared.executeQuery();
ArrayList<String> stopNameList = new ArrayList<String>();
while (rsBehav.next()) {
int numberOfRows = rsBehav.getInt(1);
String stNa = rsBehav.getString("stop_name");
// ....
if (behaviourExist.next()) {
PreparedStatement prepared = con
.prepareStatement("SELECT mac, stop_name from behaviour where mac = ?");
prepared.setString(1, macD);
ResultSet rsBehav = prepared.executeQuery();
ArrayList<String> stopNameList = new ArrayList<String>();
int numberOfRows = 0;
while (rsBehav.next()) {
++numberOfRows;
String stNa = rsBehav.getString("stop_name");
if (stNa.equals(nameShortestDistance)) {
stopNameList.add(stNa);
}
}
}
Here the variable numberOfRows will increment each time the loop runs which will give you the total number of rows in the resultSet.
I'm a MySQL user and I have been using following statements in MySQL Workbench :
(these statements are based on Select column names whose entries are not null)
SET group_concat_max_len = 4294967295;
SELECT GROUP_CONCAT(
' SELECT ',QUOTE(COLUMN_NAME),
' FROM ( select * from table_name where s3_01 = ', coloumn1,' ) abc',
' WHERE `',REPLACE(COLUMN_NAME, '`', '``'),'` IS NOT NULL',
' HAVING COUNT(*)'
SEPARATOR ' UNION ALL ')
INTO #sql
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = DATABASE()
AND TABLE_NAME = 'table_name';
PREPARE stmt FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
Although it work in my workbench, I do not know how to make it work in java.
for example, I made following code:
String sql1 = "SET group_concat_max_len = 4294967295;";
String sql2 = " SELECT GROUP_CONCAT(' SELECT ',QUOTE(COLUMN_NAME), ' FROM ( select * from ptc_weight where s3_01 = ',column1,' ) abc', ' WHERE `',REPLACE(COLUMN_NAME, '`', '``'),'` IS NOT NULL', ' HAVING COUNT(*)' SEPARATOR ' UNION ALL ') INTO #sql FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'ptc_weight'; ";
String sql3 = " PREPARE stmt FROM #sql; ";
String sql4 = " EXECUTE stmt;";
String sql5 = " DEALLOCATE PREPARE stmt;";
String[] result = getResult(sql1+sql2+sql3+sql4+sql5);
public static String[][] getResult(String sql) {
System.out.println(sql);
Connection con = null;
PreparedStatement ps = null;
ResultSet rs = null;
String[][] resultTable = null;
try {
con = getCon();
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
ResultSetMetaData result = rs.getMetaData();
int rowNum=0;
// Go to the last row
rs.last();
rowNum = rs.getRow();
// Reset row before iterating to get data
rs.beforeFirst();
int colNum = result.getColumnCount();
resultTable = new String[rowNum][colNum];
for(int itr1=0; itr1<rowNum; itr1++){
rs.next();
for(int itr2=0; itr2<colNum; itr2++){
resultTable[itr1][itr2] = rs.getObject(itr2+1).toString();
}
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
dbclose(con, ps, rs);
}// finally
return resultTable;
}
However, it does not work. I guess I made a wrong code for utilizing stored procedure, but I don't have any idea to deal with this problem.
CallableStatement callableStatement = null;
String getDBUSERByUserIdSql = "{call getDBUSERByUserId(?,?,?,?)}";
callableStatement.setInt(1, 10);
callableStatement.registerOutParameter(2, java.sql.Types.VARCHAR);
callableStatement.registerOutParameter(3, java.sql.Types.VARCHAR);
callableStatement.registerOutParameter(4, java.sql.Types.DATE);
// execute getDBUSERByUserId store procedure
callableStatement.executeUpdate();
String userName = callableStatement.getString(2);
String createdBy = callableStatement.getString(3);
Date createdDate = callableStatement.getDate(4);
System.out.println("UserName : " + userName);
System.out.println("CreatedBy : " + createdBy);
System.out.println("CreatedDate : " + createdDate);
Here Is Full Example. You can modify your code as you need.
Simple one with less argument and with resultset :
CallableStatement cstmt = con.prepareCall("{call getEmployeeDetails(?, ?)}");
cstmt.setInt("employeeId", 123);
cstmt.setInt("companyId", 456);
ResultSet rs = cstmt.executeQuery();