Iterate over the ResultSet Create a new Object for each row, to store the fields you need Add this new object to ArrayList or Hashmap or whatever you fancy Close the ResultSet, Statement and the DB connection Done EDIT: now that you have posted code, I have made a few changes to it. public List … Read more
You can use foreach here just fine. foreach ($rows as $row) { echo $row[‘id’]; echo $row[‘firstname’]; echo $row[‘lastname’]; } I think you are used to accessing the data with numerical indices (such as $row[0]), but this is not necessary. We can use associative arrays to get the data we’re after.
cursor.rowcount will usually be set to 0. If, however, you are running a statement that would never return a result set (such as INSERT without RETURNING, or SELECT … INTO), then you do not need to call .fetchall(); there won’t be a result set for such statements. Calling .execute() is enough to run the statement. … Read more
Returning a Map result using JPA Query getResultStream Since the JPA 2.2 version, you can use the getResultStream Query method to transform the List<Tuple> result into a Map<Integer, Integer>: Map<Integer, Integer> postCountByYearMap = entityManager.createQuery(“”” select YEAR(p.createdOn) as year, count(p) as postCount from Post p group by YEAR(p.createdOn) “””, Tuple.class) .getResultStream() .collect( Collectors.toMap( tuple -> ((Number) … Read more
You might try removing the BufferedWriter and just using the FileWriter directly. On a modern system there’s a good chance you’re just writing to the drive’s cache memory anyway. It takes me in the range of 4-5 seconds to write 175MB (4 million strings) — this is on a dual-core 2.4GHz Dell running Windows XP … Read more
First, you should create Statement which can be move cursor by command: Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY); Then retrieve the ResultSet as below: ResultSet rs = stmt.executeQuery(…); Move cursor to the latest row and get it: if (rs.last()) { int rows = rs.getRow(); // Move to beginning rs.beforeFirst(); … } Then rows variable will contains … Read more
Use the ResultSetMetaData class. public static boolean hasColumn(ResultSet rs, String columnName) throws SQLException { ResultSetMetaData rsmd = rs.getMetaData(); int columns = rsmd.getColumnCount(); for (int x = 1; x <= columns; x++) { if (columnName.equals(rsmd.getColumnName(x))) { return true; } } return false; } The thing I don’t understand is why this function would ever be needed. … Read more
If you have access to the prepared statement that results in this resultset, you can use connection.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY); This prepares your statement in a way that you can rewind the cursor. This is also documented in the ResultSet Javadoc In general, however, forwarding and rewinding cursors may be quite inefficient for large result sets. … Read more
You can get columns number from ResultSetMetaData: Statement st = conn.createStatement(); ResultSet rs = st.executeQuery(query); ResultSetMetaData rsmd = rs.getMetaData(); int columnsNumber = rsmd.getColumnCount();
I think there’s a way to use less memory (a fixed and not linear amount depending on data cardinality) but this imply to change the method signature. In fact we may print the Json data directly on an output stream as soon as we fetch them from the ResultSet: the already written data will be … Read more