使用Java程序中的JDBC执行多个sql SELECT查询

Question

I am trying to execute multiple SQL Queries that SELECT different columns from different tables of the same Database. The results will be pasted to an XML. Is there a way were I can merge the queries and produce a single execute statement?

Below you can find the code I use to execute a single query.

String SQLquery1="SELECT * FROM TABLE1";
String SQLquery2="SELECT P.TITLE, P.LASTNAME, P.FIRSTNAME, P.ADDRESS, PO.POSTCODE, P.SEX FROM TABLE2 P LEFT OUTER JOIN TABLE3 PO ON P.VALUE2= PO.VALUE2";
//Code that exececutes a single query
Statement stmt=null;
Connection db = null; 
ResultSet rs=null;
db = DriverManager.getConnection(url);
stmt=db.createStatement();
rs=stmt.executeQuery(SQLquery1);

I was wondering if I can use the executeQuery to execute both of these queries as a single statement or if there is another way to execute them separately. I mean do I have to execute different statements for each query?

Answer 1

I mean do I have to execute different statements for each query?

You do. If you were selecting the same columns in both queries (or at least the same # and type of columns), you could combine the queries with a UNION ALL . Since the columns differ, you must use different statements (and connections - if you want to run both queries simultaneously). If you run the queries sequentially, one connection is sufficient.