I have recently started learning laravel 5.2. I have 2 tables in postgresql DB. Parent table is subscription_master having plan_id as primary key and child table is pricing having id as primary key and plan_id as foreign key. i want to fetch all the rows from parent table and matching foreign key rows from child table. how can i use Eloquent model to get the desired result.
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In SQL in general, but in SQLite for this case, can we establish a foreign key from one table say, table in db1.db to mainTable in db2.db. That is we can use a foreign key relationship in table by referencing the primary key in mainTable, the main idea being to use this relationship to trigger ON DELETE CASCADE. (Briefly in my case, mainTable happens to be a system maintained SQLITE database, which I'd like to avoid manual finding and analyzing. If I could somehow access establish this key, life would be a lot easier).
I have made a simple relation table. All consist of three tables:
Tables for storing personal data (Table_Person)
Table for storing address data (Table_Address)
Table to store the relationship between Table_Person and Table_Address (Table_PersonAddress).
What I want to ask is can I delete the primary key in Table_PersonAddress so that Table_PersonAddress doesn't have a primary key and all that's left is the personID and addressID?
Below is an example of a database relation that I made:
enter image description here
Assuming you don't have any foreign key constraints setup on the junction table (that is, the third table which just stores relationships between people and their addresses), you could delete a person from the first table, while leaving behind the relationships in the third table. However, just because you could do this, does not mean you would want to. Most of the time, if you remove a person from the first table, you would also want to remove all of his relationships from the third table. One way to do this in SQLite is by adding cascading delete constraints to the third table, when you create it:
CREATE TABLE Table_PersonAddress (
...
CONSTRAINT fk_person
FOREIGN KEY (personID)
REFERENCES Table_Person (ID)
ON DELETE CASCADE
)
You probably would also want to add a similar constraint for the address field in the third table, since removing an address also invalidates all relationships involving that address.
Note that SQLite does not allow a cascading delete constraint to be added to table which already exists. You will have to recreate your tables somehow in order to add these constrains.
You can delete it, but my advice is to set a composite PRIMARY KEY for the 2 columns personID and addressID so each row is guaranteed to be UNIQUE.
PRIMARY KEY (personID, addressID)
and remember that in SQLite you always have the rowid column to use it as an id of the row if needed.
So create the table with this statement:
DROP TABLE IF EXISTS PersonAddress;
CREATE TABLE PersonAddress (
personID INTEGER,
addressID INTEGER,
PRIMARY KEY(personID, addressID),
FOREIGN KEY (personID) REFERENCES Person (personID) ON DELETE CASCADE,
FOREIGN KEY (addressID) REFERENCES Address (addressID) ON DELETE CASCADE
);
One more thing: why did you define personID and addressID as TEXT?
Surely SQLite is not at all strict at data type definitions, but since the columns they reference are INTEGER they also should be INTEGER.
In the PostgreSQL 11 Release Notes I found the following improvements to partitioning functionality:
Add support for PRIMARY KEY, FOREIGN KEY, indexes, and triggers on partitioned tables
I need this feature and tested it.
Create table:
CREATE TABLE public.tbl_test
(
uuid character varying(32) NOT null,
registration_date timestamp without time zone NOT NULL
)
PARTITION BY RANGE (registration_date);
Try to create Primary key:
ALTER TABLE public.tbl_test ADD CONSTRAINT pk_test PRIMARY KEY (uuid);
I get an error SQL Error [0A000]. If use composite PK (uuid, registration_date) then it's work. Because PK contains partitioning column
Conclusion: create PK in partitioning tables work with restrictions (PK need contains partitioning column).
Try to create Foreign key
CREATE TABLE public.tbl_test2
(
uuid character varying(32) NOT null,
test_uuid character varying(32) NOT null
);
ALTER TABLE tbl_test2
ADD CONSTRAINT fk_test FOREIGN KEY (test_uuid)
REFERENCES tbl_test (uuid);
I get an error SQL Error [42809]. It means FOREIGN KEY on partitioning tables not work.
Maybe i'm doing something wrong. Maybe somebody tried this functionality and know how this work.
Maybe somebody know workaround except implement constraint in the application.
PostgreSQL v12.0 will probably support foreign keys that reference partitioned tables. But this is still not guaranteed as v12.0 is still in development.
For v11 and lower versions, you may use triggers as described by depesz in these posts: part1, part2, and part3.
Update: PostgreSQL v12.0 was released on Oct 3, 2019, with this feature included
Postgres 11 only supports foreign keys from a partitioned table to a (non-partitioned) table.
Previously not even that was possible, and that's what the release notes are about.
This limitation is documented in the chapter about partitioning in the manual
While primary keys are supported on partitioned tables, foreign keys referencing partitioned tables are not supported. (Foreign key references from a partitioned table to some other table are supported.
(emphasis mine)
We have two tables in the same database but in different schemas.
i.e. foo.Table1 and bar.Table1 both with an Id column as primary key.
foo.Table1 is from an existing model, cannot be modified and is already in the database.
We want to create an ef6 code first model of bar.Table1 that will have its primary key (bar.Table1.Id) set as a foreign key of foo.Table1.Id. We have already accomplished it in SMSS but we cannot figure out how to do it in code without affecting foo.Table1.
Thank you
Is there any way in SQLite3 to have a foreign key in the main database that references columns in an attached database (or vice-versa?)
I hope to share the attached (read-only) database between multiple processes, each of which has its own (read/write) main database.
I create the parent table like this (in database 'ParentDB'):
create table Parent (id integer primary key);
Now I try this in the main database:
attach 'parent.sqlite3' as ParentDB;
create table Child (id integer not null references Parent (id),
constraint PK_Child primary key (id));
insert into ParentDB.Parent (id) values (42);
When I try it it creates the foreign key with no errors. Now I try to insert a row into the child table:
insert into Child (id) values (42);
And I get this error:
Error: no such table: main.Parent
So it seems it always assumes the parent and child tables belong to the same database.
Also the foreign key syntax does not allow you to specify which database the parent table belongs to.
Is there a workaround?
This question is related, but here both the parent and child tables are in the same attached database, whereas I have them in separate databases.
SQLite's built-in foreign key constraints do not work across databases.
The only workaround would be to manually write check constraints and triggers that do the same checking.