mybatis <sql>

The <sql> element in MyBatis is used to define reusable SQL fragments that can be included in other SQL statements. It allows you to define a piece of SQL logic that can be used in multiple places without having to repeat the code.

For example, you can define a <sql> element to generate a WHERE clause that can be used in multiple queries:

<sql id="whereClause">
<if test="name != null">
AND name = #{name}
</if>
<if test="age != null">
AND age = #{age}
</if>
</sql>

You can then include this fragment in your SQL statements like this:

<select id="getUser" resultType="User">
SELECT * FROM users
<where>
<include refid="whereClause"/>
</where>
</select>

The <include> element is used to include the SQL fragment defined by the <sql> element with the specified id.

Using <sql> and <include> elements can help simplify your SQL and make it easier to maintain.