如何使用查询从 MySQL 数据库中检索单个单元格并将其分配给 Java Netbeans Apache 中的变量

Question

首先，我将尝试使用查询来检索使用项目描述的 int min_stock 单个单元格。然后将该值放入变量中。我希望能够使变量 minStock 等于一个数字。我想用它在我的程序中进行操作。

PreparedStatement cm = con.prepareStatement(checkMinimumStock);
ResultSet minS = cm.executeQuery("SELECT min_stock FROM items WHERE item_description = '"+item+"'"); 
            int minStock = minS.getInt("min_stock");```

Answer 1

String checkMinimumStock = "SELECT min_stock FROM items WHERE item_description = ? ";

忘记在代码开头添加这个了！

Answer 2

您选择了错误的使用方式PrepareStatment。
你有两个选择：

1:
String sql = "SELECT min_stock FROM items WHERE item_description = ?";
PreparedStatement cm = con.prepareStatement(sql);
cm.setString(1, item);
ResultSet rs = cm.executeQuery();

2：
String sql = "SELECT min_stock FROM items WHERE item_description = '" + item + "'";
ResultSet rs = con.createStatement().executeQuery(sql);

然后是

if (rs.next())
int minStock = rs.getInt("min_stock");
else
//not found any match row in DB table

Answer 3

试试这个

String checkMinimumStock = "SELECT min_stock FROM items WHERE item_description = ? ";
PreparedStatement cm = con.prepareStatement(checkMinimumStock);
cm.setString(1,item);
ResultSet minS = cm.executeQuery();
if(minS.next()){
  int minStock = rs.getInt("min_stock");
}

如何使用查询从 MySQL 数据库中检索单个单元格并将其分配给 Java Netbeans Apache 中的变量

How do I retrieve a single cell from MySQL database using query and assigned it to a variable in Java Netbeans Apache

java

mysql

netbeans