The first join
CityBook Libraries wants to display book categories alongside search results. Only books with assigned categories should appear in the results.
Join the categories table to enrich the book data. The HikariSetup class is already configured for you.
本练习是课程的一部分
Querying a PostgreSQL Database in Java
练习说明
- Complete the query to join with the
categoriestable usingcategory_id. - Select the proper join type to show only books that have a category.
交互式实操练习
通过完成这段示例代码来试试这个练习。
public class Main {
public static void main(String[] args) throws SQLException {
HikariDataSource ds = HikariSetup.createDataSource();
// Join with the categories table using category_id
String query = """
SELECT b.*, c.name, c.description
FROM books b
____ JOIN ____ c on b.____ = c.____
WHERE b.publication_year >= ?
AND b.status = 'available'
ORDER BY publication_year ASC
""";
try (Connection conn = ds.getConnection();
PreparedStatement pstmt = conn.prepareStatement(query)) {
pstmt.setInt(1, 2000);
try (ResultSet rs = pstmt.executeQuery()) {
while (rs.next()) {
System.out.printf("ID: %d, Title: %s (%d), Category: %s - %s%n",
rs.getInt("book_id"), rs.getString("title"), rs.getInt("publication_year"),
rs.getString("name"), rs.getString("description"));
}
}
}
}
}