当我尝试运行下面的代码时,我得到:
You have an error in your sql Syntax; check the manual that corresponds to your MySQL server version for the right Syntax to use near ‘?’ at line 1`
String query="Select * from DB.Admin where username = ?";
PreparedStatement st=connection.prepareStatement(query);
st.setString(1,request.getParameter("loginid"));
ResultSet rst= st.executeQuery(query);
int count=0;
while(rst.next()){
count++;
}
请帮帮我.
解决方法:
您必须从executeQuery调用中删除query参数.如果提供参数,则将执行查询而不绑定任何值(有关详细信息,请参阅Statement) – 这就是语法(即?)无效的原因.
像这样执行查询:
ResultSet rst = st.executeQuery();
作为旁注:您应始终使用try-with-resources块包装Connection,PreparedStatement和ResultSet,例如:
try (ResultSet rst = st.executeQuery()) {
// read the results
}
这样,无论发生什么,您都可以确保ResultSet将被关闭.