Question

我正在使用JCBC API连接到mySQL服务器以执行一些SQL查询（创建表，删除行等）。

但是，我在以下函数中收到“类型不匹配：无法从int转换为ResultSet”错误：

private static void deleteUnpopularArtists(Statement statement, int min_rank) throws SQLException {

    String rank = Integer.toString(min_rank);
    ResultSet resultSet = statement.executeUpdate("DELETE FROM record_artist WHERE high_chart_pos < " + rank + ";");

}

我尝试使用String.valueOf(min_rank);和int rank = min_rank + "";

所以我的问题是，为什么我会收到此错误？我该怎么做才能解决它？

Answer 1

executeUpdate返回查询中受影响的行数。用于数据库写操作的ResultSet的概念没有意义

int rows = statement.executeUpdate
     ("DELETE FROM record_artist WHERE high_chart_pos < " + rank + ";");

Answer 2

1. ExecuteUpdate returns int - for update, insert and delete operations 
where the result is expected to be int ( Number of rows affected )

2. ExecuteQuery returns resultset - useful for query statements (eg. select * from table) 
where result type is resultset (data from the table)

3. execute returns boolean - when you do not know what function to use for your 
query or for unknown dynamic sql use this function.
It returns true if result is a resultSet and false if answer is an updateCount 
or no results founds

希望这有帮助!!!

“类型不匹配：无法从int转换为ResultSet”

2 个答案: