Java While loop database - java

I have two loops in the code shown below. The problem is that the first loop iterates only once. It doesn't display all the data.
st = conn.createStatement();
rs = st.executeQuery("SELECT * from geopools");
while(rs.next()){
System.out.println(rs.getInt("id"));
rs = st.executeQuery("SELECT * from Geofields where id_pool='"+rs.getInt("id")+"'");
while (rs.next()) {
System.out.println(rs.getString("name")+"//");
}
}


It is because you use the same ResultSet. Use a separate ResultSet for the second iteration:
st = conn.createStatement();
rs = st.executeQuery("SELECT * from geopools");
while(rs.next()){
System.out.println(rs.getInt("id"));
ResultSet rs2 = st.executeQuery("SELECT * from Geofields where id_pool='"+rs.getInt("id")+"'");
while (rs2.next()) {
System.out.println(rs2.getString("name")+"//");
}
}


Yes. Your second loop consumes the ResultSet.
Imagine you are looping from 1 to 10:
int i = 1;
for(; i <= 10; ++i) {
doStuff();
}
It should be obvious that doStuff() is executed 10 times. Now we change that to your loop:
int i = 1;
for(; i <= 10; ++i) {
doStuff();
for(; i <= 10; ++i) {
doOtherStuff();
}
}
Now doStuff is executed once, then we enter the inner loop. That executes 10 times and increments i. When the inner loop exits, i is 11 and the outer loop condition is met, it exits immediately.
You are doing (almost) exactly the same thing, instead of i you have a ResultSet which has a number of rows. The first loop takes one row, and prints the id from that row. Then the inner loop consumes the rest of the rows.


it works very well, but when I added a third loop I get the same problem and this is my source code:
st = conn.createStatement();
rs = st.executeQuery("SELECT * from geopools");
int idPool=0;
int idField =0;
while(rs.next()){
DefaultMutableTreeNode treeNode = new DefaultMutableTreeNode("Pool : "+rs.getString("name"));
poolNode.add(treeNode);
idPool = rs.getInt("id");
st2 = conn.createStatement();
rs2 = st2.executeQuery("SELECT * from Geofields where id_pool='"+idPool+"'");
while (rs2.next()) {
DefaultMutableTreeNode fieldsNode = new DefaultMutableTreeNode("Field : "+rs2.getString("name"));
treeNode.add(fieldsNode);
idField = rs2.getInt("id");
st3 = conn.createStatement();
rs3 = st3.executeQuery("SELECT * from geofieldsproject where id_pool='"+idPool+"'");
while (rs3.next()) {
DefaultMutableTreeNode projectsNode = new DefaultMutableTreeNode("Field : "+rs3.getString("name"));
treeNode.add(projectsNode);
}
}
}
st = null;
rs = null;
st2 = null;
rs2 = null;
st3 = null;
rs3 = null;

Related

execute query according to condition

PreparedStatement pstmt = null;
ResultSet rs = null;
List<SelectItemsDTO> listItem = new ArrayList<SelectItemsDTO>();
try {
StringBuilder query =new StringBuilder();
query = query.append(SLCMQueryConstant.GET_CollegeChid_LIST);
pstmt = conn.prepareStatement(query.toString());
pstmt.setInt(1,commonDto.getOrgID());
rs = pstmt.executeQuery();
int pid= 0;
while (rs.next()) {
pid= rs.getInt("organization_parent_id");
}
if(pid!= 0)
{
query = query.append(SLCMQueryConstant.GET_CollegeSub_LIST.toString());
pstmt = conn.prepareStatement(query.toString());
}
else
{
query = query.append(SLCMQueryConstant.GET_College_LIST.toString());
pstmt = conn.prepareStatement(query.toString());
}
pstmt.setInt(1,commonDto.getOrgID());
rs = pstmt.executeQuery();
while (rs.next()) {
SelectItemsDTO itemTo = new SelectItemsDTO();
itemTo.setItemCode(rs.getString("Organization_Name"));
itemTo.setItemIds(rs.getInt("Organization_ID"));
listItem.add(itemTo);
}
}
public static final String GET_College_LIST= " SELECT Organization_Name,Organization_ID FROM m_organization_master WHERE organization_parent_id = ? ";
public static final String GET_CollegeSub_LIST = " SELECT Organization_Name,Organization_ID FROM m_organization_master WHERE Organization_ID = ? ";
I want to execute query according to if condition .I am getting PID value from database and then used as if condition .This code seems an error no value specified for parameter 1 I have already initialized parameter for passing the values.

Storing array and accessing them

This is the coding which I have used to retrieve data from the "GeneID" column. Using this coding I can print all names under the "GeneID" column. But I want to store each and every names from the column to access those name separately. Can anyone help me with this?
String name1[] = new String[100];
int i = 0;
String query = "select distinct GeneID from gene1";
PreparedStatement pest = connection.prepareStatement(query);
ResultSet rs = pest.executeQuery();
while (rs.next()) {
name1[i] = rs.getString("GeneID");
System.out.println(name1[i]);
}
rs.close();
pest.close();

For using array you have to increment i inside the while (rs.next()) {
String name1[] = new String[100];
int i = 0;
String query = "select distinct GeneID from gene1";
PreparedStatement pest = connection.prepareStatement(query);
ResultSet rs = pest.executeQuery();
while (rs.next()) {
name1[i] = rs.getString("GeneID");
System.out.println(name1[i]);
i++;
}
rs.close();
pest.close();
}
For accessing you can iterate over the array
for(int i;i<name1.length-1;i++){
System.out.println("Id is "+name1[i]);
}
Or you can use
for (String id: name1) {
System.out.println("Id is "+name1[i]);
}
You can also use ArrayList to store variable like below
ArrayList ar=new ArrayList();
String query = "select distinct GeneID from gene1";
PreparedStatement pest = connection.prepareStatement(query);
ResultSet rs = pest.executeQuery();
while (rs.next()) {
String id = rs.getString("GeneID");
ar.add(id);
}
rs.close();
pest.close();
}
For iterating over ArrayList
for (int i = 0; i < ar.size(); i++) {
System.out.println("Id is "+ar.get(i));
}
or
for (String id : ar) {
System.out.println("Id is "+ar.get(i));
}

use arrayList, so that you can use a method of .add(), this proves much helpful
List ls=new ArrayList();
ResultSet rsp=pss.executeQuery("select * from student");
while(rsp.next()){
ls.add(rsp.getString("your_column_name"));
}
rsp.close();

Comparison of different values from ResultSet to database SQL Query

I'm new to java.I have a SQL Query that gives the following output
logtime 2014-09-02 16:05:10.0
BL1_data_SS_ST 2
BL2_data_SS_ST 2
BL3_data_SS_ST 2
BL4_data_SS_ST 1
BL5_data_SS_ST 0
BL6_data_SS_ST 2
/* continues till BL27_data_SS_ST */
st1_prmt_status_p45 1
beam_current 110.58
beam_energy 2500.0635
I have only one row in my output and 31 columns. I'm using Java and JSP .
EDIT
The above result is retrieved by the following method
public String[][] beamline_Status() {
int i = 0;
try {
con = getConnection();
stmt = con.createStatement();
String sql = "SELECT TOP 1 c.logtime, a.BL1_data_SS_ST,a.BL2_data_SS_ST,a.BL3_data_SS_ST,a.BL4_data_SS_ST,a.BL5_data_SS_ST,a.BL6_data_SS_ST,a.BL7_data_SS_ST,a.BL8_data_SS_ST,a.BL9_data_SS_ST,a.BL10_data_SS_ST,a.BL11_data_SS_ST, a.BL12_data_SS_ST,a.BL13_data_SS_ST,a.BL14_data_SS_ST,a.BL15_data_SS_ST,a.BL16_data_SS_ST,a.BL17_data_SS_ST,a.BL18_data_SS_ST,a.BL19_data_SS_ST,a.BL20_data_SS_ST,a.BL21_data_SS_ST,a.BL22_data_SS_ST,a.BL23_data_SS_ST,a.BL24_data_SS_ST,a.BL25_data_SS_ST,a.BL26_data_SS_ST,a.BL27_data_SS_ST,b.st1_prmt_status_p45,c.beam_current,c.beam_energy from INDUS2_BLFE.dbo.main_BLFE_status a inner join INDUS2_MSIS.dbo.main_MSIS_status b on a.logtime=b.logtime inner join INDUS2_BDS.dbo.DCCT c on b.logtime=c.logtime ORDER BY c.logtime DESC ";
stmt.executeQuery(sql);
rs = stmt.getResultSet();
while (rs.next()) {
for (int j = 0; j < 31; j++) {
a[i][j] = rs.getString(j + 1);
}
}
} catch (Exception e) {
System.out.println("\nException (String code):" + e);
} finally {
closeConnection(stmt, rs, con);
}
return a;
}
Now I wan to define a method which retrieve values from the ResultSet where column values are either 0 or 1. How to do that.
EDIT 2
I'm trying to retrieve the column values from resultset where column value is 1 by following code:-
public String[][] beam_CurrentStatus() {
int i = 0;
try
{
con = getConnection();
stmt = con.createStatement();
String sql = "SELECT TOP 1 c.logtime, a.BL1_data_SS_ST,a.BL2_data_SS_ST,a.BL3_data_SS_ST,a.BL4_data_SS_ST,a.BL5_data_SS_ST,a.BL6_data_SS_ST,a.BL7_data_SS_ST,a.BL8_data_SS_ST,a.BL9_data_SS_ST,a.BL10_data_SS_ST,a.BL11_data_SS_ST, a.BL12_data_SS_ST,a.BL13_data_SS_ST,a.BL14_data_SS_ST,a.BL15_data_SS_ST,a.BL16_data_SS_ST,a.BL17_data_SS_ST,a.BL18_data_SS_ST,a.BL19_data_SS_ST,a.BL20_data_SS_ST,a.BL21_data_SS_ST,a.BL22_data_SS_ST,a.BL23_data_SS_ST,a.BL24_data_SS_ST,a.BL25_data_SS_ST,a.BL26_data_SS_ST,a.BL27_data_SS_ST,b.st1_prmt_status_p45,c.beam_current,c.beam_energy from INDUS2_BLFE.dbo.main_BLFE_status a inner join INDUS2_MSIS.dbo.main_MSIS_status b on a.logtime=b.logtime inner join INDUS2_BDS.dbo.DCCT c on b.logtime=c.logtime ORDER BY c.logtime DESC ";
stmt.executeQuery(sql);
rs = stmt.getResultSet();
while (rs.next()) {
for (int j = 1; j < 31; j++) {
if ((rs.getString(j)) == "1")
a[i][j] = rs.getString(j + 1);
}
}
} catch (Exception e) {
System.out.println("\nException in:" + e);
} finally {
closeConnection(stmt, rs, con);
}
return a;
}
But the result I'm getting of above code is
[[Ljava.lang.String;#ea25c1

If you want entire table in the ResultSet and then obtain only the first and second column out of it you can do like:
Statement stmt=conn.createStatement();
ResultSet rs= stmt.executeQuery("select * from tableName");
rs.getInt(1); //assuming your column is of compatible type
rs.getInt(2);
or the other way is that you retrieve only the first two columns from the DB into your ResultSet

Copying Resultset content to arraylist and comparing both the values

In the below code I am copying resultset content to arraylist. First part of the wile loop i.e while(RS.next()) is returing the results but when cursor moves to
Next while loop i.e while(SR.next()) I am getting "result set is closed". Please help me where I am doing mistake.
String SSQ = "select DISTINCT S_NUMBER from OTG.S_R_VAL" +
" WHERE R_TS = (SELECT MAX(R_TS) FROM OTG.S_R_VAL) order by S_NUMBER";
String SDS = "SELECT DISTINCT S_NUMBER FROM OTG.S_R_VAL AS STG WHERE S_NUMBER NOT IN" +
"(SELECT S_NO FROM OTG.R_VAL AS REV WHERE STG.S_NUMBER = REV.S_NO )";
String SSR = "SELECT DISTINCT S_NO FROM OTG.R_VAL where S_NO != 'NULL' order by S_NO";
String SSO = "Select O_UID from OTG.OPTY where C_S_NO IN" +
"( SELECT DISTINCT S_NUMBER FROM OTG.S_R_VAL AS STG WHERE S_NUMBER NOT IN(SELECT S_NO FROM OTG.R_VAL AS REV WHERE STG.S_NUMBER = REV.S_NO ))";
//Statement statement;
try {
connection = DatabaseConnection.getCon();
statement = connection.createStatement();
statement1 = connection.createStatement();
statement2 = connection.createStatement();
statement3 = connection.createStatement();
statement4 = connection.createStatement();
ResultSet RS = statement1.executeQuery(selectQuery);
ResultSet DS = statement2.executeQuery(Distinct_SiebelNo);
ResultSet SR = statement3.executeQuery(SiebelNo_Rev);
ResultSet SO = statement4.executeQuery(selected_OppId);
ArrayList<String> RSList = new ArrayList<String>();
ArrayList<String> SRList = new ArrayList<String>();
/* ResultSetMetaData resultSetMetaData = RS.getMetaData();
int count = resultSetMetaData.getColumnCount();*/
int count=1;
System.out.println("******count********"+count);
while(RS.next()) {
int i = 1;
count=1;
while(i < count)
{
RSList.add(RS.getString(i++));
}
System.out.println(RS.getString("SIEBEL_NUMBER"));
RSList.add( RS.getString("SIEBEL_NUMBER"));
}
/* ResultSetMetaData resultSetMetaData1 = SR.getMetaData();
int count1 = resultSetMetaData1.getColumnCount();*/
int count1=1;
while(SR.next()) {
int i = 1;
while(i < count1)
{
SRList.add(SR.getString(i++));
}
System.out.println(SR.getString("SIEBEL_NO"));
SRList.add( SR.getString("SIEBEL_NO"));
}SR.close();
connection.commit();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}

The logic of each loop is flawed.
int count=1;//Count is being set to one
while(RS.next()) {
int i = 1;//i is being set to one
count=1;//count again set to one
while(i < count) //condition will always fail as one is never less than one
{
RSList.add(RS.getString(i++));//Code is never Reached
}
System.out.println(RS.getString("SIEBEL_NUMBER"));
RSList.add( RS.getString("SIEBEL_NUMBER"));
}
The second while is not needed. Just use this:
int count = 1;
while(RS.next()) {
RSList.add(RS.getString(count++));
System.out.println(RS.getString("SIEBEL_NUMBER"));
RSList.add( RS.getString("SIEBEL_NUMBER"));
}
EDIT
int count1=1;
while(SR.next()) {
SRList.add(SR.getString(count1++));
System.out.println(SR.getString("SIEBEL_NO"));
SRList.add( SR.getString("SIEBEL_NO"));
}
EDIT 2:
for (String s : RSList)
for(String s1 : SRList)
if (s.equals(s1))
//Do what you need

You are using the first resultset (RS) in the second loop (System.out.println line)

viewing results of mysql query in java

In java, when executing a query like :
statement stm = stm.executeQuery("select * from table1");
How can I view the results of this query on the command prompt ?
Thanks for any help

ResultSet rs = stmt.executeQuery("select * from table1");
int columns = rs.getMetaData().getColumnCount();
StringBuilder message = new StringBuilder();
while (rs.next()) {
for (int i = 1; i <= columns; i++) {
message.append(rs.getString(i) + " ");
}
message.append("\n");
}
System.out.println(message); // print table contents

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