PreparedStatement pstm = conn.prepareStatement(sql);
时间: 2024-06-05 16:09:05 浏览: 12
这行代码是在 Java 中使用 JDBC(Java Database Connectivity)连接数据库,并创建一个 PreparedStatement 对象。PreparedStatement 可以预编译 SQL 语句并将参数设置为 "?",然后在执行时再将具体的参数传入,可以防止 SQL 注入等安全问题。其中,conn 是一个已经建立好连接的 Connection 对象,而 sql 是一个字符串类型的 SQL 语句。这行代码的作用是将 sql 语句预编译为一个 PreparedStatement 对象,以便后续的操作。
相关问题
PreparedStatement pra = conn.prepareStatement(sql);
这是Java中使用JDBC进行数据库操作的语句,其中的`conn`是一个连接对象,`sql`是要执行的SQL语句。`prepareStatement`方法会返回一个`PreparedStatement`对象,它可以预编译SQL语句,提高执行效率,并且可以防止SQL注入攻击。接下来可以使用`setXXX()`方法设置SQL语句中的参数,然后调用`execute()`方法执行SQL语句。例如:
```
String sql = "SELECT * FROM users WHERE username = ? AND password = ?";
PreparedStatement pra = conn.prepareStatement(sql);
pra.setString(1, "admin");
pra.setString(2, "123456");
ResultSet rs = pra.executeQuery();
while (rs.next()) {
// 处理查询结果
}
pra.close();
conn.close();
```
以上代码中使用了`setString()`方法设置了两个参数,然后执行了一个查询语句并处理了查询结果。最后需要关闭连接和`PreparedStatement`对象,以释放资源。
rs=conn.preparestatement(sql).executeQuery
As an AI language model, I cannot determine the programming language you are using. However, the following code is a general example of how to create a prepared statement and execute a query:
```
// create a prepared statement
PreparedStatement pstmt = conn.prepareStatement("SELECT * FROM my_table WHERE id = ?");
// set parameter value
pstmt.setInt(1, 123);
// execute query and get result set
ResultSet rs = pstmt.executeQuery();
```
In this example, `conn` is a database connection object, `sql` is the SQL query string, and `rs` is the result set returned from executing the query. The `prepareStatement` method creates a prepared statement object, which can be used to execute the same query multiple times with different parameter values. The `setInt` method sets the value of the first parameter in the prepared statement to 123. Finally, the `executeQuery` method executes the query and returns the result set.