Question

我正在使用预准备语句对我的数据库执行某些操作。我的表格如下：

+--------------------------------------------------------+
|Field  |    Type  |    Size |   Key  |  Text            |
+--------------------------------------------------------+           
|X1DEL  |  Char    |     1   |     2  | Status           |  
|X1CMP  |  Zoned   |     3   |     1  | Company No.      | 
|X1ORD  |  Zoned   |     9   |     2  | Order Number     | 
|X1TYPE |  Char    |     1   |     1  | Transaction Type |
|X1ORDT |  Zoned   |     8   |     0  | Order Date       |
|X1CUST |  Char    |    10   |     0  | Customer Number  |
|X1PO   |  Char    |    20   |     0  | PO Number        |
|X1OTOT |  Zoned   |    11   |     2  | Order Total      |
+--------------------------------------------------------+

我正在为单个参数执行一个删除查询delete from my_table where field=?。我创建了2个参数的查询delete from my_table where field=? and type=? 现在我再次想要执行4到5个参数的查询。我正在编写一个delete from my_table where field=?,type=?,size=? and key=?的查询我试过这个查询但没有得到结果。

Answer 1

按照设计，use prepared statements使用任意数量的参数构建查询。

final String sql = "delete from my_table where field=? and type=? and size=? and key=?";

如果您的参数位于collection，则可以使用链接教程和"make coding easier by using a for loop or a while loop to set values for input parameters"的建议。根据您提供的type和参数数量，您需要为每个参数调用相应的.set方法。

 //assuming con (DB connection) is properly setup
 final PreparedStatment statement = con.prepareStatement(sql); 
 statement.setString(1, "X1DEL");
 statement.setString(2, "CHAR");
 statement.setInt(3,1);
 statement.setInt(4, 2);

 //... etc

您必须记住准备好的语句是1-based索引。

Answer 2

为什么在2参数示例显示正确的事情时，您是这样做的？

delete from my_table where field = ? and type = ? and size = ? and key = ?

使用包含2个以上参数的预准备语句删除记录

2 个答案: