在 Java 中检查 ResultSet 是否为空
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Check if ResultSet is empty in Java
提问by Max Pain
I am using HSQLDB in my program. I want to check if my Result Set is empty or not.
我在我的程序中使用 HSQLDB。我想检查我的结果集是否为空。
//check if empty first
if(results.next() == false){
System.out.println("empty");
}
//display results
while (results.next()) {
String data = results.getString("first_name");
//name.setText(data);
System.out.println(data);
}
The above method is not working properly. According to this postI have to call .first()or .beforeFirst()to rest the cursor to the first row, but .first()and .beforFirst()are not supported in HSQL. I also tried to add connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);but I still get the same outcome (I get the message empty and the data from the DB!!!)
What am I doing wrong here?
上述方法无法正常工作。根据这个帖子我要打电话.first()或.beforeFirst()将光标停留在第一行，但.first()和.beforFirst()在HSQL不支持。我也尝试添加connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);但我仍然得到相同的结果（我得到的消息是空的，数据来自数据库！！！）我在这里做错了什么？
采纳答案by Elliott Frisch
If I understand your objective, you could use do whileloop
如果我理解你的目标，你可以使用do while循环
if (!results.next()) {
System.out.println("empty");
} else {
//display results
do {
String data = results.getString("first_name");
//name.setText(data);
System.out.println(data);
} while (results.next());
}
Or, you could just keep a countlike so,
或者，你可以保持count这样，
int count = 0;
//display results
while (results.next()) {
String data = results.getString("first_name");
//name.setText(data);
System.out.println(data);
count++;
}
if (count < 1) {
// Didn't even read one row
}
