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Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. However, I'm having a heck of a time getting my relationships correct. There are no foreign key and primary key constraints defined in the tables. However, in the users table the userhash will be unique. I didn't design it this way, but I have to use it like this.
It prints out the correct firstname, but when I try to display the logs, it is null or empty. Am I requesting the data incorrectly for child tables or am I missing something somewhere in the domain class design? I figured the above would let me manually define the primary key and foreign key via code since it didn't exist int he tables.
No luck though. It looks like you may have to do something with in Users for the logs association to force the foreign key to be in the Logs table, as it is.
Perhaps something like:. Learn more. Asked 5 years, 10 months ago. Active 5 years, 10 months ago.Ematic tablet hard reset
Viewed times. Here is my database schema setup 2 tables : Table - Users userhash varchar firstname varchar lastname varchar Table - Logs userhash varchar accessdate date There are no foreign key and primary key constraints defined in the tables.
Any help would be appreciated. Nic Raboy Nic Raboy 3, 21 21 silver badges 24 24 bronze badges. Active Oldest Votes. Are you sure that your data are consistent? Are all the 'userhash' values in the logs table valid? Are the no null values?
The data does match up. No null values. Could there be a problem with my id field?
My tables do not have id columns so I had to map the id property to userhash in Users. Not sure what to map it to in Logs since it's more composite neither userhash and accessdate are unique on their own.
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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. Could you give me more details about this? Don't really understand about your question, Thank you.
Siesta is asking to have foreign key constraints added when you have a relation. In the example above you have a user and the user has one shipping address. In addition to data integrity, it also helps with tooling that reflects on foreign keys constraints to model the database. Hey guys, sorry i forgot to reply, and thanks pmorton this is exactly what i wanted to state in this issue.
Seems it is hard to make it database agnostic especially for postgres, it may break create table flow because of postgres is really strictly about this. Hey jinzhu.
Because the struct is little wrong i think. You should only add embed referenced struct into parent instead of this one. Id With this approach it is easy to provide this feature. So, adding UserId and User into same struct -imo- is not a good approach.
On the other hand this approach will help you on sql. NullInt64 problem. Thanks for your efforts. I means postgres is really strictly, and would throw error if the reference table doesn't exist. So you need to adjust the migration order carefully based on relations to avoid issue, and this would be tricky if two tables referenced each other. I think it is hard to know the foreign key based on above definition?
So we have to use tag to declare it if don't have UserId field, like this:. Id is not a good implementation because of it is quite confusion. Idwhat about name? Then gorm need to find out related user when query myStruct, this would be unnecessary cost if you don't require any user information. For above two structs, they relied each other, and for postgres, you can't create any references if the referred table doesn't exist.Rv surplus salvage
Similar to: db. Therefore, if we want to define the foreign key, we can have it in a function which uses the schema from struct and adds constraints via statements like below before it is imported : db. This is a pretty serious problem, as anyone using an ORM would expect proper abstraction of foreign keys with constraint. Has there been any progress at all since the last update? The following works for me with gorm v1.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. I'm trying to build a simple many2many relation between two structs, but I can't seem to get gorm to add foreign keys on the join table, which leaves orphan rows on the table when I delete a record from either one of the structs. Not sure if this is related to this issue.Oppo a7 next update
I'm experiencing the same issue using mysql. The join tables gets created but remain empty for a many2many relationship. I have tried many things from gorm documentation but I am also facing the same issue, no foreign key anywhere in my DB schema. It seems like all the associations are created only at the model level but not on DB schema.
And it is not a good way to go ahead without proper DB schema for the associations. Yogi abdusco Yeah this kind of sucks, if you use gormigrate you can get around this.
First, explicitly create the join table and migrate it before adding the many2many on the two models you want to be assiciated through the join table. Then migrate the many2many table which won't modify the created foreign key constraints on the existing explicit join table. There's another hacky solution if you don't want to use gormigrate that works okay and generates fks on the join table.
If you are automigrating to get the tables migrated initially like in an initilization script is to automigrate all the models first and then drop the join tables and re-automigrate them. I think it's a good idea to explicitly definite the join tables, but it sucks that the many2many struct tags generate the join table before explicitly creating the join table if you try to automigrate everything and add additional fields to your join table but the primary key annotation isn't added to the field.Golang ORM - Part 5 - Associations
After this initialization script is ran you can automigrate all models with the jointable Model at the end of the automigrate args. Another workaround to add the foreign keys would be to use gorm's AddForeignKey on a temporary model representing the join table. It plays well with the auto migration too.
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Open " sqlite3 "filename if err! LogMode true db. SingularTable true db. Println result if result.Dky2701 61×h 610ソリッド型 カムシェルビングセット 61× 61×h 61×h
This comment has been minimized. Sign in to view.Think twice — in two cases of very large databases I have inherited at relatively large companies, this was exactly the implementation. Aside from the 9x cost in size 36 vs. Things got really bad in one company where they had originally decided to use Latin-1 character set. When we converted to UTF-8 several of the compound-key indexes were not big enough to contain the larger strings.
We have way more than 2 billion transactions in each of several databases. So bigint is needed in some cases and that uses 8 bytes. If you have a well normalized database, as we do at my current company, each use of the key as an FK starts adding up.
Not just on disk but during joins and sorts these keys need to live in memory. And neither is free. Our database has plenty of intermediate tables that are mainly containers for the foreign keys of others, especially in 1-to-many relations.
Accounts have multiple card numbers, addresses, phone numbers, usernames, and all that. For each of these columns in a set of table with billions of accounts, the extra size of foreign keys adds up fast. Another problem is fragmentation — because UUIDs are random, they have no natural ordering so cannot be used for clustering.
A primary key is, by definition unique within its scope. It is, therefore, an obvious thing to use as a customer number, or in a URL to identify a unique page or row. I would argue that using a PK in any public context is a bad idea. The original issue with simple auto-incrementing values is that they are easily guessable as I noted above.
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Items and Manufacturers using a foreign key.
I'm following the steps at jinzhu. I get no errors nor warnings. Inspecting my tables I noticed no correlation was created. Item does not have Manufacturer field. Leads to the same result.
No foreign key is created and I'm able to insert new items with a non-existent Manufacturer. Here's what worked for me:. I would've preferred to use the mechanics outlined in gorm's documentation, but at the end of the day I just needed something that worked. Learn more. Unable to set foreign key using gorm Postgresql Ask Question.
Asked 2 years, 6 months ago. Active 7 months ago. Viewed 3k times. Model "items". Related "manufacturers". They get created with this name on Postgresql even though their model's name is singular.
So the correct way based on what I have read is to create an intersection table to represent the relationship, for example:. But what are the disadvantages of using a nullable foreign key instead of creating an intersection table? The disadvantage of a nullable foreign key is being unable to model the relationship as many-to-many, if that is what you are trying to accomplish.
Based on your edit to the question, you are effectively splitting the student table into two tables with the same key. I generally see this on tables that have way too many fields, so someone splits them into two to be more manageable I call it putting lipstick on a pig. By splitting the student table, you are making the second table optional because a record need not exist in the second table.
Which is very similar to a field not needing to be set because it can be null. If you want a one-to-many relationship, you are far better off using a single table and allowing the school ID to be null in the student table. There is no reason to avoid nulls in fields, even for a foreign key. That signifies that the foreign relationship is optional: developers and DBAs understand that clearly, and the underlying database engine certainly should work fine. If you are concerned about joins, do not worry.
There are well-define semantics for how joins work with null fields. By using a single table, you can join two tables instead of three. When there are a lot of NULL values in the foreign key column, your programs will have to deal with this mostly empty column for each and every record they process. Using an intersection table avoids this, there will be only link records necessary where the equivalent foreign key would not be NULL otherwise.
So using an intersection table is just a form of optimization, only sensible for a specific case, and especially nowadays, where disk space and memory became cheaper, much less frequently needed.
Note that "Fundamentals of Database Systems" was originally written more than 20 years ago I found a reference to the second edition fromand I guess that recommendation was already in there at that time. Beforespace optimization was probably much more important than today, since mass storage was still more expensive and computers and networks were much slower than today.Ships
As a side note to a picky comment: the above statement is just trying to anticipate what the author of "Fundamentals of Database Systems" had in mind with his recommendation, I guess he was making a rough, general statement, valid for most systems. In some databases there are other possible optimizations like "sparse columns" which make the use of an intersection table even more obsolete.
Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. After a very long time and reading lots of documentatin, SO questions and code samples I tried to do the following:. This "worked" in the sense that it really got the result filled up with AgentMetadata.
However, it was not the correct metadata. GetGlobalDefault defaultAgent. OS instead of getting the 1. Another thing that bothers me is that I had to explicitly specify the foreign key names, whereas according to the documentation it seems that specifiying them is not needed or at least can be achieved by adding a tag:.
Here I only added a tag for the OS column, however, I tried concatenating the foreign key names and neither option seemed to have an effect on the result.
Without explicitly specifying the foreign key names in the API, the related data would just not be read. Having the pass the names to the query means that my DB mapping is not consolidated in a single place and I don't like that. Can my scenario be solved? Can I have a composite foreign key? Can I specify all ORM properties in a single place?
Learn more. Foreign keys and related data with gorm Ask Question.
Asked 2 years, 9 months ago. Active 1 year, 10 months ago. Viewed 1k times. I'm using golang and gorm to talk to a MySQL database. Indeed, when I turned on the gorm logs I saw that it ran the query: [ ] [ Flimzy Dina Dina 1, 10 10 silver badges 24 24 bronze badges. Active Oldest Votes. Sign up or log in Sign up using Google.
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