使用JDBC编写查询

Question

I am working with JDBC and PostgreSQL and I have to do the following:

/*
 * Return list of film titles whose length is equal to or greater
 * than the minimum length, and less than or equal to the maximum
 * length.
 */
public List<String> getFilmTitlesBasedOnLengthRange(Connection connection,
                int minLength, int maxLength) {
        List<String> result = new LinkedList<String>();

        return result;
}

I tried to first solve this problem by writing a query in PostgreSQL (not sure if it's even correct):

SELECT title
FROM dv_film A, dv_film B
WHERE (A.length >= (COUNT(length) ASC LIMIT 1)) AND (B.length >= (COUNT(length) DESC LIMIT 1));

The dv_film relation is:

CREATE TABLE dv_film (
    film_id      integer, 
    title        varchar(50), 
    description  text, 
    length       smallint, 
    rating       mpaa_rating
);

My attempt at trying to solve the problem is:

public List<String> getFilmTitlesBasedOnLengthRange(Connection connection,
                        int minLength, int maxLength) {
                List<String> result = new LinkedList<String>();

                PreparedStatement st = conn.prepareStatement("SELECT title FROM dv_film A, dv_film B WHERE (? >= (COUNT(length) ASC LIMIT 1)) AND (? >= (COUNT(length) DESC LIMIT 1));");

                return result;
        }

Answer 1

your statement:

PreparedStatement st = conn.prepareStatement("SELECT title FROM dv_film A, dv_film B WHERE (? >= (COUNT(length) ASC LIMIT 1)) AND (? >= (COUNT(length) DESC LIMIT 1));");

Here you are trying to pass column names to PreparedStatement and you cannot set column names as PreparedStatement values. You can only set column values as PreparedStatement values