Question

输入的电影成功保存到moviesTbl表，但是当我尝试显示自动编号字段'MovieID'时，我检索到错误。

public void updateMovies(String update, String title, java.sql.Date releaseDate, String genre) throws SQLException {
    Connection connection = dc.DatabaseConnection();
    PreparedStatement statement = connection.prepareStatement(update); //the insert statement is prepared 
    statement.setString(1, title); //each attribute is set individually
    statement.setDate(2, releaseDate);
    statement.setString(3, genre);
    statement.executeUpdate();
    statement.close();
    ResultSet ID = dc.query("Select * from moviesTbl where title = " + title + " and genre = " + genre + " and releaseDate = " + releaseDate); //a ResultSet is prepared for the ID of the movie 
    while(ID.next()) { //the ResultSet is prepared for display
        int movieID = ID.getInt("MovieID");
        JOptionPane.showMessageDialog(null, "The movie's ID is " + movieID + ". Please record it on the DVD for future reference.");
    }
}

错误：

Exception in thread "main" net.ucanaccess.jdbc.UcanaccessSQLException: user lacks privilege or object not found: HARRY
at net.ucanaccess.jdbc.UcanaccessConnection.prepareStatement(UcanaccessConnection.java:462)
at movierentalstore.DatabaseConnection.query(DatabaseConnection.java:63)
at movierentalstore.QueryingTheDatabase.updateMovies(QueryingTheDatabase.java:181)
at movierentalstore.MovieRentalStore1.<init>(MovieRentalStore1.java:77)
at movierentalstore.MovieRentalStore1.main(MovieRentalStore1.java:25)
Caused by: java.sql.SQLSyntaxErrorException: user lacks privilege or object not found: HARRY
at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
at org.hsqldb.jdbc.JDBCPreparedStatement.<init>(Unknown Source)
at org.hsqldb.jdbc.JDBCConnection.prepareStatement(Unknown Source)
at net.ucanaccess.jdbc.UcanaccessConnection.prepareStatement(UcanaccessConnection.java:460)
      ... 4 more
      Caused by: org.hsqldb.HsqlException: user lacks privilege or object not found: HARRY
at org.hsqldb.error.Error.error(Unknown Source)
at org.hsqldb.error.Error.error(Unknown Source)
at org.hsqldb.ExpressionColumn.checkColumnsResolved(Unknown Source)
at org.hsqldb.QueryExpression.resolve(Unknown Source)
at org.hsqldb.ParserDQL.compileCursorSpecification(Unknown Source)
at org.hsqldb.ParserCommand.compilePart(Unknown Source)
at org.hsqldb.ParserCommand.compileStatement(Unknown Source)
at org.hsqldb.Session.compileStatement(Unknown Source)
at org.hsqldb.StatementManager.compile(Unknown Source)
at org.hsqldb.Session.execute(Unknown Source)
... 7 more

Java结果：1

Answer 1

JDBC使用数据库引擎的功能返回生成的密钥。这可以防止需要对数据库供应商进行特定的，最重要的是：即使两个人同时执行相同的数据库插入，您也会获得正确的ID。

try (PreparedStatement stm = conn.prepareStatement(
        "INSERT INTO moviesTbl  (title, ...) VALUES(?, ? ...)")) {
    stm.setString(1, title);
    stm.setString(2, ...);
    ...
    int updateCount = stm.executeUpdate();
    if (updateCount != 0) {
        try (ResultSet genKeys = stm.getGeneratedKeys()) {
            if (genKeys.next()) { // At most 1 record inserted
                // Normally only one key generated per record.
                int id = genKeys.getInt(0);
                ...
            }
        } // Close result set.
    }
} // Closes stm

它有点冗长，但理论上你可以有一些带有几条记录的声明，并且每条记录有多条生成密钥。

错误可能源于SELECT，其中字符串常量不在撇号（'）之间。也应该是PreparedStatement。

从ResultSet显示自动编号字段时出错

1 个答案: