[英]How to dynamically select a resultMap and append an incrementing integer value to a “non-existent” column in MyBatis?
I have a certain resultset in MYSQL database using the sakila database on actors and its related tables: 我在MYSQL数据库中使用了关于actors及其相关表的sakila数据库的某个结果集:
actor_id first_name last_name title
1 PENELOPE GUINESS ANACONDA CONFESSIONS
1 PENELOPE GUINESS ANGELS LIFE
I have successfully map the following data in MyBatis Plus using the following result map: 我已使用以下结果映射在MyBatis Plus中成功映射了以下数据:
<resultMap id="actor" type="java.util.TreeMap">
<result property="id" column="id" />
<result property="firstname" column="first_name" />
<result property="lastname" column="last_name" />
<collection property="movies" javaType="ArrayList" resultMap="movies" />
</resultMap>
<resultMap id="movies" type="java.util.TreeMap">
<result property="title" column="title" />
</resultMap>
The SQL query looked like this: SQL查询看起来像这样:
<select id="getActors" parameterType="ActorDetailsDTO" resultMap="actor">
select
a.actor_id,
first_name,
last_name,
title
from actor a left join
film_actor fa on a.actor_id = fa.actor_id left join
film f on fa.film_id = f.film_id
where a.actor_id = #{id}
</select>
This, in turn achieve the following result: 这反过来又实现了以下结果:
result :{
"id" : 1,
"movies":[
{
title : "ANACONDA CONFESSIONS"
},
{
title : "ANGELS LIFE"
},
],
"firstname" : "PENELOPE",
"lastname" : "GUINESS"
}
But I find it difficult to add a "non-existent" column name "movielist" with a value of "blockbuster X" where X is an incrementing number from 1 to N. 但我发现很难添加一个“不存在的”列名“movielist”,其值为“blockbuster X”,其中X是从1到N的递增数字。
I hope to achieve this result: 我希望达到这个结果:
result :{
"id" : 1,
"movies":[
{
"movielist" : "blockbuster 1",
"title" : "ANACONDA CONFESSIONS"
},
{
"movielist" : "blockbuster 2",
"title" : "ANGELS LIFE"
},
],
"firstname" : "PENELOPE",
"lastname" : "GUINESS"
}
And, of course, if I have two or more actors, the "blockbuster X" will rest back to 1 to the second actor. 而且,当然,如果我有两个或更多的演员,“重磅炸弹X”将重新回到第二个演员的1。
What I've done in the SQL query is I add a variable counter, but the count just continues on counting, not resetting for a new actor. 我在SQL查询中所做的是添加一个变量计数器,但计数只是继续计数,而不是为新的actor重置。
Thank you for any help you could give. 感谢您提供任何帮助。
It should be possible with variables, but here is another approach using a subquery. 应该可以使用变量,但这是使用子查询的另一种方法。
<select id="getActors" resultMap="actor">
select
a.actor_id,
first_name,
last_name,
fa.film_id,
concat('blockbuster ', (select count(*) from film_actor fa2
where a.actor_id = fa2.actor_id and fa2.film_id <= fa.film_id)) movielist,
title
from actor a
left join film_actor fa on a.actor_id = fa.actor_id
left join film f on fa.film_id = f.film_id
order by a.actor_id, fa.film_id;
</select>
And here are the result maps. 这是结果图。
<id />
elements are added to improve efficiency. <id />
元素以提高效率。
<resultMap id="actor" type="java.util.TreeMap">
<id property="id" column="actor_id" />
<result property="firstname" column="first_name" />
<result property="lastname" column="last_name" />
<collection property="movies" javaType="list"
resultMap="movies" />
</resultMap>
<resultMap id="movies" type="java.util.TreeMap">
<id column="film_id" /><!-- not stored in map -->
<result property="movielist" column="movielist"
javaType="string" /><!-- CONCAT returns VARBINARY -->
<result property="title" column="title" />
</resultMap>
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