How is the usage of “apply” in MyBatis?

In MyBatis, the and tags can be used to reuse and combine SQL fragments. The tag can be used to obtain the automatically generated primary key value when inserting data. The tag is used to apply a SQL fragment and pass parameters, similar to a function call.

Here is how to use the tag:

<apply id="applyExample" resultType="java.lang.Integer">
    SELECT *
    FROM users
    WHERE id = #{userId}
</apply>

In the example above, the tag defines an SQL statement that includes a parameter #{userId}. When using this SQL statement, the value of the userId parameter can be passed in, then the SQL statement will be executed and the results returned.