What does @ in sql mean?

The @ symbol in SQL is used to specify variable parameters in a query, which is helpful to improve code readability, prevent SQL injection attacks, and improve performance. Syntax: @parameter_name, where parameter_name is the name of the parameter.

The meaning of the @ symbol in SQL

In SQL, the @ symbol is used to specify a parameter. Parameters are the mutable part of the query and can be replaced by different values ​​while the query is executed.

Purpose

Using the @ symbol has several benefits:

• Improve code readability: Enable query Easier to read and understand because the parameters are separated from the actual values.
• Prevent SQL injection attacks: By passing user input as parameters, you can prevent malicious users from modifying the query and performing unauthorized operations.
• Improve performance: By using parameterized queries, the database can precompile the query and store it in the cache, thus improving performance.

Syntax

The syntax for specifying parameters using the @ symbol is as follows:

<code>@parameter_name</code>

where parameter_name is the name of the parameter .

Example

The following is an example query that uses the @ symbol to specify a parameter named @age:

<code class="sql">SELECT * FROM users WHERE age > @age;</code>

When executing this query, different @age values ​​can be provided to find users of different age groups. For example:

<code class="sql">-- 查找年龄大于 30 岁的人
SELECT * FROM users WHERE age > 30;

-- 查找年龄大于 25 岁的人
SELECT * FROM users WHERE age > 25;</code>

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