java - try catch block 不适用于 sql

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我有以下java代码:

ResultSet rs2 = stmt.executeQuery("select * from teacher");  

        try
        {rs2.getInt("fee");
          System.out.println("found");
          stmt.executeUpdate("alter table teacher drop fee  ");
        }catch(SQLException e){
            System.out.println("not found");
            System.err.print(e);
            stmt.executeUpdate("alter table teacher add fee int ");
        } 

尝试似乎从未被调用。

Answer 1

您需要执行 rs2.next() 来获取第一行(以及后续行)。如:

ResultSet rs2 = stmt.executeQuery("select * from teacher");  

//rs2.next(); // reads one row!
  rs2.first();


try {
  rs2.getInt("fee");
  System.out.println("found");
  stmt.executeUpdate("alter table teacher drop fee  ");
} catch(SQLException e) {
  System.out.println("not found");
  System.err.print(e);
  stmt.executeUpdate("alter table teacher add fee int ");
}