ER_DUP_FIELDNAME: Duplicate column name

It is very common for databases to stick with underscore style column names, especially for relationships like user_id, category_id, space_id…

By default TypeORM names all relation columns in camelCase spaceId, userId… You can override this behavior in TypeORM like so

@ManyToOne(type => Space, space => space.posts, { nullable: false })
@JoinColumn({ name: "space_id" }) // NOTICE I am telling TypeORM to use space_id
space: Space;

Now the database column is space_id instead of spaceId…good. All works well across the board until CRUD does a JOIN. I have only tested on a OneToMany. My basic setup is a POSTS entity that can have ONE space. So a basic OneToMany/ManyToOne relation is setup.

When your JOIN query runs it actually runs 2 queries. The first query errors with ER_DUP_FIELDNAME: Duplicate column name space_id because you assume you can call one of the columns as ‘space_id’ yourself, but its already taken. Here is your first JOIN query that errors

SELECT
	DISTINCT `distinctAlias`.`Post_id` as ids_Post_id
FROM (
	SELECT
		`Post`.`id` AS `Post_id`,
		`Post`.`slug` AS `Post_slug`,
		`Post`.`title` AS `Post_title`,
		`Post`.`body` AS `Post_body`,
		`Post`.`hidden` AS `Post_hidden`,
		`Post`.`deleted` AS `Post_deleted`,
		`Post`.`indexed_at` AS `Post_indexed_at`,
		`Post`.`created_at` AS `Post_created_at`,
		`Post`.`updated_at` AS `Post_updated_at`,
------------------
PROBLEM IS HERE
		`space`.`id` AS `space_id`,
		`space`.`name` AS `space_name`,
		`space`.`section` AS `space_section`,
		`space`.`slug` AS `space_slug`,
		`space`.`order` AS `space_order`,
------------------
		`Post`.`parent_id`,
		`Post`.`space_id`,
		`Post`.`format_id`,
		`Post`.`created_by`,
		`Post`.`updated_by`
	FROM
		`posts` `Post`
		INNER JOIN `spaces` `space` ON `space`.`id`=`Post`.`space_id`
) `distinctAlias`
ORDER BY `Post_id` ASC LIMIT 25

Notice you are adding all your AS statements to the space table and assuming you can just append the column name after an _ as space_id, as space_name etc…well space_id is already used. If you were to change your AS statement to something that couldn’t possibly clash like space_table_id for example… or double understoce space__id, space__name etc…

Because of this I cannot set any of my ids to use underscores now.

[mreschke]

I have some new information on this. If I comment out the maxLimit: 25, line in my controller the query changes to just a single proper JOIN without running 2 queries, the first of which crashes with the duplicate space_id column error. Just like in #280, not sure why adding maxLimit would later one JOIN into 2 queries with an IN statement. Either way, the first query still crashes with duplicate column.

[michaelyali]

@kop7 set an alias for test relation too