Re: JDBC - Need to declare variables for values in insert statement - Mailing list pgsql-general

I would recommend the reading of the excellent The Java Tutorial, that has a very well explained section about JDBC:
http://docs.oracle.com/javase/tutorial/jdbc/index.html


and the chapter about PreparedStatements:
http://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html


Regards,

Edson Richter


Em 28/01/2013 17:09, Bob Futrelle escreveu:

Thanks to Edson and Dave for lightning responses.

I'm confident that your answers will do the job.

I'll follow up on the advice AFTER I get my coffee ;-)

I'm really focused on the NLP content of my research,

but I need a DB infrastructure to do it right.

(Not a bunch of files as in ancient times.)

 --- Bob

On Mon, Jan 28, 2013 at 1:59 PM, Edson Richter <edsonrichter@hotmail.com> wrote:

You have two options:

st.execute("insert into hello values ('bKey', "+f1()+")");

or

PreparedStatement st = db.prepareStatement("insert into hello values ('bKey', ?)");
st.setInteger(1, f1());


where 1 is the first parameter, 2 is the second parameter, and so on.


Regards,

Edson Richter



Em 28/01/2013 16:50, Bob Futrelle escreveu:

Here's a small, but complete code example - Bob

package us.tsos.dbs.pg;

import java.sql.*;

/**

 * This is an effort to get a computed value from a Java function

 * (or data object) included properly in the VALUES entries.

 * So, how can I declare an SQL variable and set its value to some Java value?

 * Results viewed in pgAdmin3  with query 'select * from public.hello'.

 *

 * Jar in classpath is postgresql-9.2-1002.jdbc4.jar

 * 

 * @version 0.1  Mon Jan 28 EST 2013

 * @author Bob Futrelle

 */

public class JDBCVariableTest {

Connection db;

Statement st;

Boolean boo;

public static void main(String[] args) throws SQLException {

JDBCVariableTest testIt = new JDBCVariableTest();

testIt.helloVariables();

}

public int f1() { return 3;}

public void helloVariables() throws SQLException  {

int intVar = f1();  // OK in Java, but SQL/JDBC?

try {

db = DriverManager.getConnection("jdbc:postgresql:Articles", "robertfutrelle", "<my pw>");

st = db.createStatement();

boo  = st.execute("CREATE TABLE IF NOT EXISTS hello ( Name VARCHAR NOT NULL PRIMARY KEY, value int)");

// Declare ....  ??

// INSTEAD OF THE LITERAL 4 VALUE (which works)

// how do I declare a variable and assign the f1() return value to it

// and then include it so the value 3 appears in the inserted record?

//st.execute("insert into hello values('aKey',4)");

st.execute("insert into hello values('bKey',4)");

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

On Mon, Jan 28, 2013 at 8:39 AM, Dave Cramer <pg@fastcrypt.com> wrote:

Bob,

Can you provide a snippet of code so I can understand what you mean by declare ?

Dave Cramer

dave.cramer(at)credativ(dot)ca
http://www.credativ.ca

On Mon, Jan 28, 2013 at 7:11 AM, Bob Futrelle <bob.futrelle@gmail.com> wrote:

Do the declare statements and insert all have to be done in one statement execute()?

That is, what is the scope of variables I declare?

I see a variety of syntax examples, some for older versions?

I'm using pg 9.2.2, so what are the rules/syntax for declaring and using variables?

Use case: I collect metadata from XML articles such as title, journalName, volume, year.  For each article I need to create a pg table record and insert the values for the various metadata items in the article.

This is my first post to this list.

Thanks,

 - Bob