如何从结果集中获取计数？

Question

ResultSet rs = statement.executeQuery("SELECT COUNT(DISTINCT `id`) FROM `users`");

在MySQL中，我有“ 5”的答案，如何从Java的结果集中获取这5？ 诠释

Answer 1

将其作为int列获取：

int count = -1;
if (rs.next()) {
    count = rs.getInt(1);
}

Answer 2

尝试给COUNT（DISTINCT ID ）加上别名，然后从ResultSet中检索别名。 如果您最终在以后向查询中添加了更多的逻辑，则这将更易读且易于维护。

ResultSet rs = statement.executeQuery("SELECT COUNT(DISTINCT `id`) as NUM_ROWS FROM `users`");

int count = -1;
if(rs.next())
{
    count = rs.getInt("NUM_ROWS");

}