# Running queries

When you don’t need a transaction or run single queries, you can run queries directly on the pool; the pool will use one of its connection to run the query and return the result to you.

Here is how to run simple queries:

    client
      .query("SELECT * FROM users WHERE id='julien'")
      .execute()
      .onComplete(ar -> {
      if (ar.succeeded()) {
        RowSet<Row> result = ar.result();
        System.out.println("Got " + result.size() + " rows ");
      } else {
        System.out.println("Failure: " + ar.cause().getMessage());
      }
    });

## Prepared queries

You can do the same with prepared queries.

The SQL string can refer to parameters by position, using the database syntax {PREPARED_PARAMS}

    client
      .preparedQuery("SELECT * FROM users WHERE id=?")
      .execute(Tuple.of("julien"))
      .onComplete(ar -> {
      if (ar.succeeded()) {
        RowSet<Row> rows = ar.result();
        System.out.println("Got " + rows.size() + " rows ");
      } else {
        System.out.println("Failure: " + ar.cause().getMessage());
      }
    });

Query methods provides an asynchronous `RowSet` instance that works for SELECT queries

    client
      .preparedQuery("SELECT first_name, last_name FROM users")
      .execute()
      .onComplete(ar -> {
      if (ar.succeeded()) {
        RowSet<Row> rows = ar.result();
        for (Row row : rows) {
          System.out.println("User " + row.getString(0) + " " + row.getString(1));
        }
      } else {
        System.out.println("Failure: " + ar.cause().getMessage());
      }
    });

or UPDATE/INSERT queries:

    client
      .preparedQuery("INSERT INTO users (first_name, last_name) VALUES (?, ?)")
      .execute(Tuple.of("Julien", "Viet"))
      .onComplete(ar -> {
      if (ar.succeeded()) {
        RowSet<Row> rows = ar.result();
        System.out.println(rows.rowCount());
      } else {
        System.out.println("Failure: " + ar.cause().getMessage());
      }
    });

The `Row` gives you access to your data by index

    System.out.println("User " + row.getString(0) + " " + row.getString(1));

Caution | Column indexes start at 0, not at 1.

Alternatively, data can be retrieved by name:

    System.out.println("User " + row.getString("first_name") + " " + row.getString("last_name"));

The client will not do any magic here and the column name is identified with the name in the table regardless of how your SQL text is.

You can access a wide variety of of types

    String firstName = row.getString("first_name");
    Boolean male = row.getBoolean("male");
    Integer age = row.getInteger("age");

You can use cached prepared statements to execute one-shot prepared queries:

    connectOptions.setCachePreparedStatements(true);
    client
      .preparedQuery("SELECT * FROM users WHERE id = ?")
      .execute(Tuple.of("julien"))
      .onComplete(ar -> {
        if (ar.succeeded()) {
          RowSet<Row> rows = ar.result();
          System.out.println("Got " + rows.size() + " rows ");
        } else {
          System.out.println("Failure: " + ar.cause().getMessage());
        }
      });

You can create a `PreparedStatement` and manage the lifecycle by yourself.

    sqlConnection
      .prepare("SELECT * FROM users WHERE id = ?")
      .onComplete(ar -> {
        if (ar.succeeded()) {
          PreparedStatement preparedStatement = ar.result();
          preparedStatement.query()
            .execute(Tuple.of("julien"))
            .onComplete(ar2 -> {
              if (ar2.succeeded()) {
                RowSet<Row> rows = ar2.result();
                System.out.println("Got " + rows.size() + " rows ");
                preparedStatement.close();
              } else {
                System.out.println("Failure: " + ar2.cause().getMessage());
              }
            });
        } else {
          System.out.println("Failure: " + ar.cause().getMessage());
        }
      });

## Batches

You can execute prepared batch

    List<Tuple> batch = new ArrayList<>();
    batch.add(Tuple.of("julien", "Julien Viet"));
    batch.add(Tuple.of("emad", "Emad Alblueshi"));

    // Execute the prepared batch
    client
      .preparedQuery("INSERT INTO USERS (id, name) VALUES (?, ?)")
      .executeBatch(batch)
      .onComplete(res -> {
      if (res.succeeded()) {

        // Process rows
        RowSet<Row> rows = res.result();
      } else {
        System.out.println("Batch failed " + res.cause());
      }
    });