小编ech*_*aze的帖子

我一直试图弄清楚为什么下面的代码没有在我的ResultSet中生成任何数据:

String sql = "SELECT STUDENT FROM SCHOOL WHERE SCHOOL = ? ";
PreparedStatement prepStmt = conn.prepareStatement(sql);
prepStmt.setString(1, "Waterloo");
ResultSet rs = prepStmt.executeQuery();

另一方面,以下运行正常:

String sql = "SELECT STUDENT FROM SCHOOL WHERE SCHOOL = 'Waterloo' ";
PreparedStatement prepStmt = conn.prepareStatement(sql);
ResultSet rs = prepStmt.executeQuery();

SCHOOL的数据类型为CHAR(9字节).我也尝试过:而不是setString:

String sql = "SELECT STUDENT FROM SCHOOL WHERE SCHOOL = ? ";
PreparedStatement prepStmt = conn.prepareStatement(sql);
String school = "Waterloo";
Reader reader = new CharArrayReader(school.toCharArray());
prepStmt.setCharacterStream(1, reader, 9);
prepStmt.setString(1, "Waterloo");
ResultSet rs = prepStmt.executeQuery();

我完全坚持接下来要调查的内容; …

有没有办法约束一个列(比如说"ID")来跟随一个创建的序列(比如"ID_SEQ")？

如果没有自动约束,手动插入可能会使整个序列失控.可以做些什么来解决这个问题？只需拨打NextVal两次？

...最好是用Java.这是我有的:

//x choose y
public static double choose(int x, int y) {
    if (y < 0 || y > x) return 0;
    if (y == 0 || y == x) return 1;

    double answer = 1;
    for (int i = x-y+1; i <= x; i++) {
        answer = answer * i;
    }
    for (int j = y; j > 1; j--) {
        answer = answer / j;
    }
    return answer;
}

我想知道是否有更好的方法来做到这一点？

有没有办法指定一个ANT文件只运行其中的一个/部分/全部？