# MyBatis - XML
## elements
1. cache
- 해당 네임스페이스 설정
2. cache-ref
- 다른 네임스페이스 설정 참조
3. resultMap
- DB Data를 Object에 로드하는 방법 정의
4. sql
- SQL 재사용
5. insert
6. update
7. delete
8. select
## select
<select id="selectPerson" parameterType="int" resultType="hashmap">
SELECT * FROM PERSON WHERE ID = #{id}
</select>
<select
id="selectPerson"
parameterType="int"
parameterMap="deprecated"
resultType="hashmap"
resultMap="personResultMap">
### parameter
#{PreparedStatement}
- JDBC 사용하면 PreparedStatement에는 "?" 형태로 파라미터 전달
## insert, update, delete
- id: PK
- useGeneratedKeys, keyProperty: Id 자동 생성
<insert id="insertAuthor" useGeneratedKeys="true" keyProperty="id">
insert into
Author (id,username,password,email,bio)
values
(#{id},#{username},#{password},#{email},#{bio})
</insert>
<update id="updateAuthor">
update Author set
username = #{username},
password = #{password},
email = #{email},
bio = #{bio}
where id = #{id}
</update>
<delete id="deleteAuthor">
delete from Author where id = #{id}
</delete>
<insert
id="insertAuthor"
parameterType="domain.blog.Author"
resultMap="someMap"
resultType="int">
<update
id="updateAuthor"
parameterType="domain.blog.Author"
resultMap="someMap"
resultType="int">
<delete
id="deleteAuthor"
parameterType="domain.blog.Author"
resultMap="someMap"
resultType="int">
## sql
<sql id="userColumns">
${alias}.id,
${alias}.username,
${alias}.password
</sql>
<select id="selectUsers" resultType="map">
select
<include refid="userColumns"><property name="alias" value="t1"/></include>,
<include refid="userColumns"><property name="alias" value="t2"/></include>
from some_table t1
cross join some_table t2
</select>
<sql id="sometable">
${prefix}Table
</sql>
<sql id="someinclude">
from
<include refid="${include_target}"/>
</sql>
<select id="select" resultType="map">
select
field1, field2, field3
<include refid="someinclude">
<property name="prefix" value="Some"/>
<property name="include_target" value="sometable"/>
</include>
</select>
## parameters
- null 값을 걸러내려면, #{parameters, JdbcType=string} 이런 식으로 설정 가능
<insert id="insertUser" parameterType="User">
insert into
users (id, username, password)
values
(#{id}, #{username}, #{password})
</insert>
- sql 구문에 별칭 지정
<select id="selectUsers" resultType="User">
select
user_id as "id",
user_name as "userName",
hashed_password as "hashedPassword"
from some_table
where id = #{id}
</select>
- resultMap에 별칭 지정
<select id="selectUsers" resultMap="userResultMap">
select user_id, user_name, hashed_password
from some_table
where id = #{id}
</select>
<resultMap id="userResultMap" type="User">
<id property="id" column="user_id" />
<result property="username" column="user_name"/>
<result property="password" column="hashed_password"/>
<association property="author" javaType="Author">
<id property="id" column="author_id"/>
<result property="username" column="author_username"/>
<result property="password" column="author_password"/>
<result property="email" column="author_email"/>
<result property="bio" column="author_bio"/>
<result property="favouriteSection" column="author_favourite_section"/>
</association>
<collection property="posts" ofType="Post">
<id property="id" column="post_id"/>
<result property="subject" column="post_subject"/>
<association property="author" javaType="Author"/>
<collection property="comments" ofType="Comment">
<id property="id" column="comment_id"/>
</collection>
</resultMap>
### association, collection
- association: has-one
- collection: has-many
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