找不到java.sql.sqlexception列 [英] java.sql.sqlexception column not found

问题描述

我正在尝试从事务表的tr_id(主键)中找到最大编号.
这是表格及其布局.

I am trying to find max no from tr_id (primary key) in transaction table.
Here is the table and it's layout.

这是我的线.

Here is my cord.

             try {
                ResultSet rs = db.getData("SELECT MAX(tr_id) FROM transaction");
                ResultSetMetaData meta = rs.getMetaData();
                for (int index = 1; index <= meta.getColumnCount(); index++) {
                    System.out.println("Column " + index + " is named " +    meta.getColumnName(index));
                }
                if (rs.first()) {
                    int tr_id = rs.getInt("tr_id");
               }

我正在使用JDBC连接.当我运行此电源线时，出现此错误.

I'm using JDBC connection. When I'm running this cord I'm getting this error.

        Column 1 is named MAX(tr_id)
        java.sql.SQLException: Column 'tr_id' not found.
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910)
    at com.mysql.jdbc.ResultSet.findColumn(ResultSet.java:955)
    at com.mysql.jdbc.ResultSet.getInt(ResultSet.java:2570)
    at Controler.InvoiceFinalising.saveInvoice(InvoiceFinalising.java:57)
  etc..

事情是当我搜索"tr_id"列名称转到Max(tr_id)

The thing is when I'm searching out as "tr_id" column name goes to Max(tr_id)

推荐答案

这是因为SQL查询中的列名是max(tr_id).您可以将其写为

This is because the column name in your sql query is max(tr_id). You can write it as

ResultSet rs = db.getData("SELECT MAX(tr_id) as tr_id FROM transaction");

现在您将能够获得它.

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