Two of three SQL stmts execute: third results in table does not exist exception

[GGP]

I attempt to collect data from a database three times in one method,
all using one connection. The first two queries execute without any
problem. However, the third fires an sql exception:

java.sql.SQLSyntaxErrorException: Table/View 'TABLENAME' does not
exist.

I connect to the database using a connection class, as follows:

public class MyDBConnection {

public static final String DRIVER_NAME =
"org.apache.derby.jdbc.ClientDriver";
public static final String DATABASE_URL = "jdbc:derby://localhost:
1527/cfdb";
public Connection myConnection;

public MyDBConnection() {}

public void init() {
Class.forName(DRIVER_NAME);
myConnection =
DriverManager.getConnection(DATABASE_URL,"usnm","pswd");
}
.... [getters and setters deleted]

I then query the database from within a UI constructor like this:

public class MainUCInterface extends javax.swing.JFrame {

MyDBConnection myConnection = new MyDBConnection();
Connection con = null;
Statement stmt = null;
ResultSet rs = null;

public MainUCInterface() throws SQLException {
initComponents();

myConnection.init();
con = myConnection.getMyConnection();

stmt = con.createStatement();
rs = stmt.executeQuery("select CONTYPEID, CONTYPENAME from
CONTYPES order by CONTYPENAME"); //This query executes fine

Statement stmt2 = null;
ResultSet rs2 = null;
stmt2 = con.createStatement();
rs2 = stmt2.executeQuery("select CONTYPEID, CONTYPENAME from
CONTYPES where CONTYPEID = " + iConvTyp); //iConvTyp is an integer,
and this query also executes fine.

ResultSet rs3 = null;
Statement stmt3 = null;
stmt3 = con.createStatement();

String tableName = strConvTyp + "CF";
String unitName = strConvTyp + "Name";
String unitID = strConvTyp + "ID";

String sqlListData = "select " + unitID + ", " + unitName + "
from " + tableName;
rs3 = stmt3.executeQuery(sqlListData); //This is where the
error occurs. All the strings in stmt3 are fine (correct spelling,
etc.)

A couple of additional notes:

1. The first two queries are on the same table. I tried
reconstructing the third table, and I just finished rebuilding the
whole database from scratch--it didn't help.

2. There is no relational structure to the database. It's just a
group of tables that hold data I need to retrieve to provide
functionality to the app. I don't know if this is a relevant point or
not.

3. Metadata on the database indicates that there are no tables present
(which would account for the error, but not the successful queries).
I'm not sure why con.getMetaData isn't seeing my tables.

Any ideas? I really appreciate the help.

Greg.

 

[Daniel Pitts]

I attempt to collect data from a database three times in one method,
all using one connection. The first two queries execute without any
problem. However, the third fires an sql exception:

java.sql.SQLSyntaxErrorException: Table/View 'TABLENAME' does not
exist.

I connect to the database using a connection class, as follows:

public class MyDBConnection {

public static final String DRIVER_NAME =
"org.apache.derby.jdbc.ClientDriver";
public static final String DATABASE_URL = "jdbc:derby://localhost:
1527/cfdb";
public Connection myConnection;

public MyDBConnection() {}

public void init() {
Class.forName(DRIVER_NAME);
myConnection =
DriverManager.getConnection(DATABASE_URL,"usnm","pswd");
}
... [getters and setters deleted]

I then query the database from within a UI constructor like this:

public class MainUCInterface extends javax.swing.JFrame {

MyDBConnection myConnection = new MyDBConnection();
Connection con = null;
Statement stmt = null;
ResultSet rs = null;

public MainUCInterface() throws SQLException {
initComponents();

myConnection.init();
con = myConnection.getMyConnection();

stmt = con.createStatement();
rs = stmt.executeQuery("select CONTYPEID, CONTYPENAME from
CONTYPES order by CONTYPENAME"); //This query executes fine

Statement stmt2 = null;
ResultSet rs2 = null;
stmt2 = con.createStatement();
rs2 = stmt2.executeQuery("select CONTYPEID, CONTYPENAME from
CONTYPES where CONTYPEID = " + iConvTyp); //iConvTyp is an integer,
and this query also executes fine.

ResultSet rs3 = null;
Statement stmt3 = null;
stmt3 = con.createStatement();

String tableName = strConvTyp + "CF";
String unitName = strConvTyp + "Name";
String unitID = strConvTyp + "ID";

String sqlListData = "select " + unitID + ", " + unitName + "
from " + tableName;
rs3 = stmt3.executeQuery(sqlListData); //This is where the
error occurs. All the strings in stmt3 are fine (correct spelling,
etc.)

My guess is that strConType + "CF" isn't producing a valid table
name... Have you verified that by debugging?

A couple of additional notes:

1. The first two queries are on the same table. I tried
reconstructing the third table, and I just finished rebuilding the
whole database from scratch--it didn't help.

2. There is no relational structure to the database. It's just a
group of tables that hold data I need to retrieve to provide
functionality to the app. I don't know if this is a relevant point or
not.

Its not necessarily relevant to your question, but it may explain the
difficulty you have working it...
It appears to me you have the following concepts:
you have a "Con" (what ever that is), which is an abstract concept...
You are expecting all "Cons" to have a type, and a name.
Also, Cons have an associated "Unit". Its not clear from your code
what kind of relationship (1->1, many->1, many->many) that Units have
to Con...
In any case, I might suggest altering your schema a little bit to
include relational data... That IS the main purpose of a database (if
not, use files for god sakes).

Table Contype should have a primary key, contypeId (maybe is the
primary key), and contypeName
Table Unit should have a primary key (possible unitId), a conTypeId
(may be a foreign key to Contype, might not be), and Name.

you're query could then be simplified: SELECT Contype.*, Unit.* FROM
Contype, Unit WHERE Unit.conTypeId = Contype.conTypeId.

From that, you should be able to get all the information you need.

Hope this helps,
Daniel.

 

[Paul Tomblin]

String sqlListData = "select " + unitID + ", " + unitName + "
from " + tableName;
rs3 = stmt3.executeQuery(sqlListData); //This is where the
error occurs. All the strings in stmt3 are fine (correct spelling,
etc.)

Print out the sqlListData string, and paste it into an interactive SQL
client to verify that it's correct. 99% of the time, you've forgotten a
space or a comma or something.