mybatis <if> else

Mybatis provides a way to conditionally include SQL statements using the `<if>` and `<choose>` tags.

You can use the `<if>` tag to add a condition to your SQL query. Here's an example:

<select id="getUserById" resultType="User">
  SELECT * FROM users
  WHERE id = #{id}
  <if test="name != null">
    AND name = #{name}
  </if>
</select>

In this example, the SQL query will include the additional `AND name = #{name}` condition only if the `name` parameter is not null.

You can also use the `<choose>` tag along with `<when>` and `<otherwise>` tags to implement conditional logic with multiple options. Here's an example:

<select id="getUserByCriteria" resultType="User">
  SELECT * FROM users
  WHERE
  <choose>
    <when test="name != null">
      name = #{name}
    </when>
    <when test="email != null">
      email = #{email}
    </when>
    <otherwise>
      id = #{id}
    </otherwise>
  </choose>
</select>

In this example, the SQL query will check for different criteria based on the provided parameters. If `name` is not null, it will search by name. If `email` is not null, it will search by email. Otherwise, it will default to searching by ID.

These conditional tags provide flexibility in building dynamic SQL queries based on different conditions.