oracle 如何从java代码中的数据库表中获取Max id
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How to get Max id from table of database in java code
提问by Vinit Vikash
I want to write code which give max id from the table but it is throwing error.
我想编写从表中给出最大 id 的代码，但它抛出错误。
code:
代码：
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection con = DriverManager.getConnection("XXXXX", "XXXX", "XXX");
Statement st2 = con.createStatement();
ResultSet idMax = st2.executeQuery("select nvl(max(work_id),0) from workdetails");
int id2 = idMax.getInt(0); // throw error: Invalid column index
System.out.println(id2);
// ****************************
int id2 = idMax.getInt("work_id");
System.out.println(id2); // throw error: ResultSet.next was not called
回答by giorashc
A result set starts at a dummy record and should be advanced to the real first record by calling the nextmethod :
结果集从一个虚拟记录开始，应该通过调用以下next方法前进到真正的第一条记录：
ResultSet idMax = st2.executeQuery("select nvl(max(work_id),0) max_id from workdetails");
int id2 = -1;
if (idMax.next()) {
id2 = idMax.getInt("max_id");
}
回答by Rakesh Juyal
You missed
你错过了
idMax.next();
This will set the pointer to the first row. Then only you have to use
这会将指针设置为第一行。那么只有你必须使用
idMax.get ( 1 );
So, your code goes like this:
所以，你的代码是这样的：
ResultSet idMax = st2.executeQuery("select nvl(max(work_id),0) from workdetails");
int id2 = 0;
if ( idMax.next() ){
id2 = idMax.getInt(1);
}
System.out.println(id2);
