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Return value of multi-table union query resultType General data returned by parameter type select id from t_car_car SELECT deptname FROM t_car_run where deptid = #{deptid} GROUP BY deptname Query according to a field

The returned type is entity class, because the query result data is the data of fields in entity class.

select number from t_car_car where id = #{carid} Query result is multiple records, stored in list Return

The returned type is entity class, because the query result data is the data of fields in entity class.

select * from t_car_car multi-table union query

t_car_car

t_car_driver

t_car_cardriver

The two fields stored in t_car_cardriver are the primary key id of t_car_car and t_car_driver respectively.

solutions

The return type of resultType is java.util.Map.

All the data stored in the List is returned.

select driverid from t_car_cardriver where carid = #{id}

2. Create a new entity class

It stores the field names required in the query results.

// TCarCarDriverprivate Long carid;private Long driverid;

The return type is the entity class

select driver id from t_car_cardriver where carid = #{id} multi-table query, return nested list of results

Multi-level nesting of collections returns results using resultMap,collection using resultMap again

select tc.id as tid, tci.id as iid, tciw.id as wid, tmq.id as qid, access_key, secret_key, outer_chain_name, outer_chain_document, intention_name, question, word_slot, word_slot_miss_question, entity_type_ids from t_chain tc left join t_chain_intention tci on tc.id = tci.chain_id left join t_chain_intention_word tciw on tci.id = tciw.intention_id left join t_multi_question tmq on tci.id = tmq.parent_id where tc.id = #{id} and tc.deleted = 0 above is about the content of this article "how MyBatis realizes the return value of multi-table joint query resultType". I believe everyone has a certain understanding. I hope the content shared by Xiaobian will be helpful to everyone. If you want to know more relevant knowledge content, please pay attention to the industry information channel.

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