<sql:update> Tag

JSP 标准标签库 JSP Standard Tag Library

The <sql:update> tag is used to execute a SQL statement that returns no value, such as SQL INSERT, UPDATE, and DELETE statements.

Syntax Format

<sql:update var="<string>" scope="<string>" sql="<string>" dataSource="<string>"/>

Attributes

The <sql:update> tag has the following attributes:

Attribute	Description	Required	Default Value
sql	The SQL command to be executed (does not return a ResultSet object)	no	Body
dataSource	The database connection to use (overrides the default value)	no	Default database
var	The variable used to store the number of affected rows	no	None
scope	The scope of the var attribute	no	Page

Program Example

First, you need to create an Employees table in the TEST database, then add a few records to the table. The specific steps are as follows:

Step 1:

Open CMD, change the directory to the installation directory:

C:\>
C:\>cd Program Files\MySQL\bin
C:\Program Files\MySQL\bin>

Step 2:

C:\Program Files\MySQL\bin>mysql -u root -p
Enter password: ********
mysql>

Step 3:

Create the Employees table in the TEST database:

mysql> use TEST;
mysql> create table Employees
    (
     id int not null,
     age int not null,
     first varchar (255),
     last varchar (255)
    );
Query OK, 0 rows affected (0.08 sec)
mysql>

Create Data Records:

Finally, create a few records in the Employees table:

mysql> INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali');
Query OK, 1 row affected (0.05 sec)
 
mysql> INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma');
Query OK, 1 row affected (0.00 sec)
 
mysql> INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan');
Query OK, 1 row affected (0.00 sec)
 
mysql> INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal');
Query OK, 1 row affected (0.00 sec)
 
mysql>

Now, write a JSP file and use the <sql:update> tag to execute an SQL INSERT statement:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.io.*,java.util.*,java.sql.*"%>
<%@ page import="javax.servlet.http.*,javax.servlet.*" %>
<%@ 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:update 标签</title>
</head>
<body>
 
<sql:setDataSource var="snapshot" driver="com.mysql.jdbc.Driver"
     url="jdbc:mysql://localhost/TEST"
     user="root"  password="pass123"/>

<sql:update dataSource="${snapshot}" var="count">
   INSERT INTO Employees VALUES (104, 2, 'Nuha', 'Ali');
</sql:update>

<sql:query dataSource="${snapshot}" var="result">
   SELECT * from Employees;
</sql:query>
 
<table border="1" width="100%">
<tr>
<th>Emp ID</th>
<th>First Name</th>
<th>Last Name</th>
<th>Age</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.age}"/></td>
</tr>
</c:forEach>
</table>

</body>
</html>

The result is as follows:

sql-update

The usage of SQL UPDATE and DELETE statements is similar to the INSERT statement.

In sql:update, if you need to use variables, you can usesql:param。

<sql:update dataSource="${snapshot}" var="count">
  DELETE FROM Employees WHERE Id = ?
  <sql:param value="${empId}" />
</sql:update>