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    <p>The H2 in-memory database stores data in memory inside the JVM. When the JVM exits, this data is lost. </p> <p>I suspect that what you are doing is similar to the two Java classes below. One of these classes creates a table and the other tries to insert into it:</p> <pre><code>import java.sql.*; public class CreateTable { public static void main(String[] args) throws Exception { DriverManager.registerDriver(new org.h2.Driver()); Connection c = DriverManager.getConnection("jdbc:h2:mem:test"); PreparedStatement stmt = c.prepareStatement("CREATE TABLE PERSON (ID INT PRIMARY KEY, FIRSTNAME VARCHAR(64), LASTNAME VARCHAR(64))"); stmt.execute(); stmt.close(); c.close(); } } </code></pre> <p>and</p> <pre><code>import java.sql.*; public class InsertIntoTable { public static void main(String[] args) throws Exception { DriverManager.registerDriver(new org.h2.Driver()); Connection c = DriverManager.getConnection("jdbc:h2:mem:test"); PreparedStatement stmt = c.prepareStatement("INSERT INTO PERSON (ID, FIRSTNAME, LASTNAME) VALUES (1, 'John', 'Doe')"); stmt.execute(); stmt.close(); c.close(); } } </code></pre> <p>When I ran these classes one after the other, I got the following output:</p> <pre> C:\Users\Luke\stuff>java CreateTable C:\Users\Luke\stuff>java InsertIntoTable Exception in thread "main" org.h2.jdbc.JdbcSQLException: Table "PERSON" not found; SQL statement: INSERT INTO PERSON (ID, FIRSTNAME, LASTNAME) VALUES (1, 'John', 'Doe') [42102-154] at org.h2.message.DbException.getJdbcSQLException(DbException.java:327) at org.h2.message.DbException.get(DbException.java:167) at org.h2.message.DbException.get(DbException.java:144) ... </pre> <p>As soon as the first <code>java</code> process exits, the table created by <code>CreateTable</code> no longer exists. So, when the InsertIntoTable class comes along, there's no table for it to insert into.</p> <p>When I changed the connection strings to <code>jdbc:h2:test</code>, I found that there was no such error. I also found that a file <code>test.h2.db</code> had appeared. This was where H2 had put the table, and since it had been stored on disk, the table was still there for the InsertIntoTable class to find.</p>
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    1. POH2 in-memory database. Table not found
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    1. USLuke Woodward
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    1. COPlease note that the `registerDriver()` call is unnecessary: First of: a simple Class.forName() does the same for most JDBC drivers **and** (more importantly) it's completely unnecessary for Java 6 und up, which auto-detects (compatible) JDBC drivers on the classpath.
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      1. USJoachim Sauer
    2. COAn in memory db exists only as long as the program that owns the memory is running? Wow, I had no idea >_< But really, I know what I'm trying to do. Reading your answer, I'm not sure you do.
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    3. CO@Jorn: I might not know what you're trying to do, I'm guessing based on what information you provided. It may have been more helpful to provide an SSCCE (http://sscce.org/) demonstrating your problem - I wouldn't call your question 'complete' in that respect. I provided the above answer because there are people on SO (newcomers to programming, mainly) that might think that an 'in-memory' database stores the data in the computer's memory somewhere where it could survive between program invocations. Your question wasn't complete enough to convince me you weren't one of these people.
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