如何使用SQL查询结果作为Java中变量的值？

Question

I have a below query

SELECT CONVERT(VARCHAR(8),(select TOP 1 LBD=latest_date 
FROM some_table
WHERE latest_date < GETDATE() 
ORDER BY latest_date DESC), 112) AS [YYYYMMDD]

which will give me a value like 20150324 for example.

Now I have a variable var in Java.

I want var to equal the result of the query (so today, it would be var = 20150324, and tomorrow it could be something completely different).

How would I accomplish this?

Answer 1

I guess you are asking how to access the database from java. Java has an API to talk to any database you have a driver for. Its called JDBC.

For SQLServer get the driver from microsoft, or alternatively use jtds (open source). Add the driver into your project and follow a tutorial on JDBC how to use it (eg http://docs.oracle.com/javase/tutorial/jdbc/ ).

Answer 2

Your code would look something like this. You would need to get the appropriate jdbc driver and configure the url appropriately, but this is a small sample of how you would do it.

import java.sql.*;

class DoQuery {

    public static void main (String[] args) {
        try {
            String url = "jdbc:sqlserver://localhost;databaseName=AdventureWorks;integratedSecurity=true;";
            Connection conn = DriverManager.getConnection(url,"","");
            Statement stmt = conn.createStatement();
            ResultSet rs;

            rs = stmt.executeQuery("SELECT CONVERT(VARCHAR(8),(select TOP 1 LBD=latest_date FROM some_table WHERE latest_date < GETDATE() ORDER BY latest_date DESC), 112) AS [YYYYMMDD]");
            while ( rs.next() ) {
                String myDate = rs.getString("YYYYMMDD");
                System.out.println(myDate);
            }
            conn.close();
        } catch (Exception e) {
            System.err.println("Got an exception! ");
            System.err.println(e.getMessage());
        }
    }
}