Syntax Error when the column name contains underscore - sql

Question

I can compile but can't execute the following code
with the error (using Postgres):
Fatal database error
ERROR: syntax error at or near "as"
Position: 13
import java.sql.*;
public class JDBCExample
{
private static final String JDBC_DRIVER = "org.postgresql.Driver";
private static final String URL = "jdbc:postgresql://hostname/database";
private static final String USERNAME = "username";
private static final String PASSWORD = "password";
public static void main(String[] args) throws Exception
{
Connection dbConn = null;
Statement query = null;
ResultSet results = null;
Class.forName(JDBC_DRIVER);
try
{
dbConn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
}
catch (SQLException e)
{
System.out.println("Unable to connect to database\n"+e.getMessage());
System.exit(1);
}
try
{
query = dbConn.createStatement();
results = query.executeQuery("select 20_5 as name from flowshop_optimums");
while (results.next())
{
System.out.println(results.getString("name"));
}
dbConn.close();
}
catch (SQLException e)
{
System.out.println("Fatal database error\n"+e.getMessage());
try
{
dbConn.close();
}
catch (SQLException x) {}
System.exit(1);
}
} // main
} // Example

Answer 1

It's not the underscore, it's the fact that the column name starts with a number. You'd need to escape this.
For MySQL, use backticks.
select `20_5` as name from flowshop_optimums
For SQL Server, use square brackets.
select [20_5] as name from flowshop_optimums
For PostgreSQL, use double quotes.
select "20_5" as name from flowshop_optimums

Answer 2

results = query.executeQuery("select \"20_5\" as name from flowshop_optimums");
But you should really change that column name.

Answer 3

Try this: results = query.executeQuery("select '20_5' as name from flowshop_optimums");

Answer 4

You need to enclose 20_5 with backticks or brackets, depending on whether or not you're using MySQL or SQLServer, respectively.