<sql:dateParam>
《sql:dateParam》标记用作《sql:query》和《sql:update》标记的嵌套操作,以提供值占位符的日期和时间值。 如果提供了null值,则占位符的值设置为SQL NULL 。
属性 (Attribute)
《sql:dateParam》标记具有以下属性 -
属性 | 描述 | 需要 | 默认 |
---|---|---|---|
Value | 要设置的date参数的值(java.util.Date) | No | Body |
type | DATE(仅限日期),TIME(仅限时间)或TIMESTAMP(日期和时间) | No | TIMESTAMP |
例子 (Example)
首先从基本概念开始,让我们在TEST数据库中创建一个简单的表Students表,并在该表中创建一些记录,如下所示 -
Step 1
打开Command Prompt并切换到安装目录,如下所示 -
C:\>
C:\>cd Program Files\MySQL\bin
C:\Program Files\MySQL\bin>
Step 2
登录数据库如下 -
C:\Program Files\MySQL\bin>mysql -u root -p
Enter password: ********
mysql>
Step 3
在TEST数据库中创建Employee表,如下所示 -
mysql> use TEST;
mysql> create table Students
(
id int not null,
first varchar (255),
last varchar (255),
dob date
);
Query OK, 0 rows affected (0.08 sec)
mysql>
创建数据记录 (Create Data Records)
我们现在将在Employee表中创建一些记录,如下所示 -
mysql> INSERT INTO Students
VALUES (100, 'Zara', 'Ali', '2002/05/16');
Query OK, 1 row affected (0.05 sec)
mysql> INSERT INTO Students
VALUES (101, 'Mahnaz', 'Fatma', '1978/11/28');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Students
VALUES (102, 'Zaid', 'Khan', '1980/10/10');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Students
VALUES (103, 'Sumit', 'Mittal', '1971/05/08');
Query OK, 1 row affected (0.00 sec)
mysql>
现在让我们编写一个JSP,它将使用《sql:update》标记以及《sql:param》标记和《sql:dataParam》标记来执行SQL UPDATE语句来更新Zara的出生日期 -
<%@ page import = "java.io.*,java.util.*,java.sql.*"%>
<%@ page import = "javax.servlet.http.*,javax.servlet.*" %>
<%@ page import = "java.util.Date,java.text.*" %>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/sql" prefix = "sql"%>
<html>
<head>
<title>JSTL sql:dataParam Tag</title>
</head>
<body>
<sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost/TEST" user = "root" password = "pass123"/>
<%
Date DoB = new Date("2001/12/16");
int studentId = 100;
%>
<sql:update dataSource = "${snapshot}" var = "count">
UPDATE Students SET dob = ? WHERE Id = ?
<sql:dateParam value = "<%=DoB%>" type = "DATE" />
<sql:param value = "<%=studentId%>" />
</sql:update>
<sql:query dataSource = "${snapshot}" var = "result">
SELECT * from Students;
</sql:query>
<table border = "1" width="100%">
<tr>
<th>Emp ID</th>
<th>First Name</th>
<th>Last Name</th>
<th>DoB</th>
</tr>
<c:forEach var = "row" items = "${result.rows}">
<tr>
<td> <c:out value = "${row.id}"/></td>
<td> <c:out value = "${row.first}"/></td>
<td> <c:out value = "${row.last}"/></td>
<td> <c:out value = "${row.dob}"/></td>
</tr>
</c:forEach>
</table>
</body>
</html>
访问上面的JSP,将显示以下结果。 从2002/05/16到2001/12/16的dob为ID = 100的记录 -
+-------------+----------------+-----------------+-----------------+
| Emp ID | First Name | Last Name | DoB |
+-------------+----------------+-----------------+-----------------+
| 100 | Zara | Ali | 2001-12-16 |
| 101 | Mahnaz | Fatma | 1978-11-28 |
| 102 | Zaid | Khan | 1980-10-10 |
| 103 | Sumit | Mittal | 1971-05-08 |
+-------------+----------------+-----------------+-----------------+