# How to add a new relation to an existing join field **URL:** \ **Category:** Elasticsearch\ **Created:** [October 13, 2017, 6:06am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827 "2017-10-13T06:06:17Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 13, 2017, 6:06am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/1 "2017-10-13T06:06:17Z")
hi，guys I use Elasticsearch and the version is 6.0 ,I created a parent-child relationship field in accordance with the official document.The document said “It is possible to add a new relation to an existing join field.”,But did not tell how to do it specifically.I tried many ways without success,The elasticsearch return the same error “Field [\_parent\_join] is defined twice in [doc]”,I want to know how to do it. thanks! ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [October 13, 2017, 6:27am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/2 "2017-10-13T06:27:14Z")
What is it you are trying to achieve? ---
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 13, 2017, 6:43am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/3 "2017-10-13T06:43:05Z")
Just want to know how to update the join field. ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [October 13, 2017, 6:45am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/4 "2017-10-13T06:45:11Z")
Are you looking to move a child from one parent to another? ---
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 13, 2017, 6:51am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/5 "2017-10-13T06:51:48Z")
I created a join field in accordance with the official document，the question and the answer。Now，I want to add another field named “commet”，This field is the answer field’s son 。How to add existed join field。thanks The document said “It is possible to add a new relation to an existing join field.” ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [October 13, 2017, 7:00am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/6 "2017-10-13T07:00:48Z")
It sounds like you are looking for [this example](https://www.elastic.co/guide/en/elasticsearch/reference/6.0/parent-join.html#_multiple_levels_of_parent_join). ---
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 13, 2017, 7:28am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/7 "2017-10-13T07:28:02Z")
thanks！，But how to add a new relation to an existing join field？ ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [October 13, 2017, 8:00am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/8 "2017-10-13T08:00:46Z")
I am not sure I follow what you are trying to do. What does the structure you want to implement look like? ---
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 13, 2017, 11:30am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/9 "2017-10-13T11:30:33Z")
![image](https://us1.discourse-cdn.com/elastic/original/3X/9/0/90b8a7cedf12e6adcec143cbbfe5211260a39f92.jpg) ---
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 13, 2017, 11:36am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/10 "2017-10-13T11:36:42Z")
![image](https://us1.discourse-cdn.com/elastic/original/3X/6/b/6b8cec1ca0db9043d80edaaf0efd52328ec095e5.png) Specific details how to do it ---
**Author:** ![pancs\_li](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@pancs\_li](https://discuss.elastic.co/u/pancs_li)\ **Post date:** [October 16, 2017, 3:27am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/11 "2017-10-16T03:27:25Z")
how to update? ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [November 13, 2017, 3:27am UTC](https://discuss.elastic.co/t/how-to-add-a-new-relation-to-an-existing-join-field/103827/12 "2017-11-13T03:27:49Z")
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