从数据库删除行有什么问题? [英] What's the problem with deleting a row from database?
问题描述
我想从数据库中删除一行，但这行不通.我有2个例外:-NumberFormatException:空(用于Servlet中的parseInt部分)-PSQLException:错误:关系患者"不存在...但是它确实存在！你能帮我解决我的问题吗?
I want to delete a row from my database, but it doesn't work. I've got 2 exception: - NumberFormatException: null (it's for the parseInt part in the Servlet) - PSQLException: ERROR: relation "patients" does not exist... but it does exist! Can u help me to solve my problem?
DB.java(只是方法)
DB.java (just the method)
public int deletePatient(int patID) {
try {
if (conn != null) {
String delete = "DELETE FROM \"Patients\" WHERE Patients.PatientID = ?";
PreparedStatement pstmt = conn.prepareStatement(delete);
pstmt.setInt(1, patID);
affectedRows = pstmt.executeUpdate();
} else {
System.out.println("Connection is not created! 5");
}
} catch (SQLException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
return affectedRows;
}
return affectedRows;
}
ServletP.java(只是方法)
ServletP.java (just the method)
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException, NumberFormatException {
try {
int patID = Integer.parseInt(request.getParameter("patID2"));
db.deletePatient(patID);
} catch (NumberFormatException n) {
n.printStackTrace();
}
PrintWriter writer = response.getWriter();
String htmlRespone = "<html>";
htmlRespone += "<h2>Action is done!</h2>";
htmlRespone += "<a href=\"/WebApp/patients\">Back</a>";
htmlRespone += "</html>";
writer.println(htmlRespone);
}
jsp:
<div>
<form method="POST" action="patients">
<table border="2" align="center">
<tr>
<td>ID:</td>
<td><input type="text" name="patID2"></td>
<td><input type="submit" value="Delete"></td>
</tr>
</table>
</form>
</div>
推荐答案
显然，您使用双引号创建了表(开始时这是一个非常糟糕的主意).完成此操作后，您必须始终 将表名和列名用双引号括起来-随处可见.
Apparently you created your table(s) using double quotes (which is a really bad idea to begin with). Once you do that, you have to always enclose your table and column names in double quotes - everywhere.
所以
"DELETE FROM \"Patients\" WHERE Patients.PatientID = ?"
应为:
"DELETE FROM \"Patients\" WHERE \"Patients\".\"PatientID\" = ?"
这篇关于从数据库删除行有什么问题?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
