sql parameters
时间: 2023-09-21 12:03:38 浏览: 48
SQL parameters are values that are used in SQL statements to filter, sort, or update data in a database. They are placeholders that are replaced with actual values at runtime, which helps to prevent SQL injection attacks and improve performance.
In SQL, parameters are typically defined using a question mark (?) or a named parameter syntax. For example, in a prepared statement, you might define a parameter like this:
```
SELECT * FROM customers WHERE last_name = ?
```
When you execute the statement, you would provide the actual value for the parameter, like this:
```
PreparedStatement stmt = conn.prepareStatement(query);
stmt.setString(1, "Smith");
ResultSet rs = stmt.executeQuery();
```
In this example, the parameter is a string value that is used to filter the results by last name. By using a parameter instead of embedding the value directly in the SQL statement, you can avoid SQL injection attacks and improve performance by allowing the database to optimize the query execution plan.