mybatis <if else

MyBatis provides a powerful feature called dynamic SQL, which allows you to conditionally include or exclude parts of a SQL statement using the `<if>` and `<choose>` tags. The `<if>` tag is used for conditional statements, including the usage of "if-else" logic.

Here's an example of how you can use `<if>` and `<choose>` tags in MyBatis:

<select id="getUserList" resultType="User">
  SELECT * FROM users
  <where>
    <if test="name != null">
      AND name = #{name}
    </if>
    <if test="age != null">
      AND age = #{age}
    </if>
    <choose>
      <when test="order == 'name'">
        ORDER BY name
      </when>
      <when test="order == 'age'">
        ORDER BY age
      </when>
      <otherwise>
        ORDER BY id
      </otherwise>
    </choose>
  </where>
</select>

In this example, the `<if>` tags are used to conditionally add the corresponding SQL clauses based on the provided parameters. The `<choose>` tag acts as an "if-else" statement, where the first matching `<when>` condition is executed, and if none of the conditions match, the `<otherwise>` block is executed.

So, depending on the values of the `name`, `age`, and `order` parameters, the generated SQL query will vary accordingly.