I have a set of companies and for each of them, I need to generate a UUID in another table.
companies table
detail_id (currently NULL for all companies)
details table
id
uuid
date
...
I'd like to update all companies with newly created detail like this:
UPDATE companies
SET details_id =
(
INSERT INTO details
(uuid, date)
VALUES (uuid_generate_v1(), now()::date)
RETURNING id
)
But that gives me a syntax error since I can't use INSERT INTO inside UPDATE.
What is a proper way to create a row in the details table and immediately set the newly created id in the companies table?
(I am using Postgres)
You can use a data-modifying CTE:
with new_rows as (
INSERT INTO details ("uuid", "date")
VALUES (uuid_generate_v1(), current_date)
RETURNING id
)
update companies
set details_id = new_rows.id
from new_rows
Related
Hello i have problem i have table
CREATE TABLE doctor(
idDoc SERIAL PRIMARY KEY,
meds TEXT[]
);
I want to store only unique values if my user enter same meds inside
Table before user insert
id
meds
1
{Nalfon,Ocufen,Actron}
After user insert (insert is Actron,Soma,Robaxin) i want update and have in table old values and new values ( Actron is same)
if I UPDATE table with new values I will get
UPDATE doctor SET meds='{Actron,Soma,Robaxin}') WHERE id=1;
id
meds
1
{Actron,Soma,Robaxin}
But i want
id
meds
1
{Nalfon,Ocufen,Actron,Soma,Robaxin}
I don't know how to check if new value is same like value in table and only insert/update table to have unique values.
Given your data structure, you can unnest the existing meds, add in the new ones, and re-aggregate as a unique array:
UPDATE doctor d
SET meds = (select array_agg(distinct med)
from (select med
from unnest('{Actron,Soma,Robaxin}'::text[]) u(med)
union all
select med
from unnest(d.meds) u(med)
) m
)
WHERE idDoc = 1;
Here is a db<>fiddle.
That said, you might consider a junction table with one row per doctor and medicine. That is the more traditional SQL representation for a many-to-many relationship.
Consider the following table:
CREATE TABLE key_phrase(
id SERIAL PRIMARY KEY NOT NULL,
body TEXT UNIQUE
)
I'd like to do the following:
Create a record with the given body if it doesn't already exist.
Return the id of the newly created record, or the id of the existing record if a new record was not created.
Ensure the serial id is not incremented on conflicts.
I've tried a few methods, the most simple including basic usage of DO NOTHING:
INSERT INTO key_phrase(body) VALUES ('example') ON CONFLICT DO NOTHING RETURNING id
However, this will only return an id if a new record is created.
I've also tried the following:
WITH ins AS (
INSERT INTO key_phrase (body)
VALUES (:phrase)
ON CONFLICT (body) DO UPDATE
SET body = NULL
WHERE FALSE
RETURNING id
)
SELECT id FROM ins
UNION ALL
SELECT id FROM key_phrase
WHERE body = :phrase
LIMIT 1;
This will return the id of a newly created record or the id of the existing record. However, it causes the serial primary to be bumped, causing gaps whenever a new record is created.
So how can one perform a conditional insert (upsert) that fulfills the 3 requirements mentioned earlier?
I suspect that you are looking for something like:
with
data as (select :phrase as body),
ins as (
insert into key_phrase (body)
select body
from data d
where not exists (select 1 from key_phrase kp where kp.body = d.body)
returning id
)
select id from ins
union all
select kp.id
from key_phrase kp
inner join data d on d.body = kp.body
The main difference with your original code is that this uses not exists to skip already inserted phrases rather than on conflict. I moved the declaration of the parameter to a CTE to make things easier to follow, but it doesn't have to be that way, we could do:
with
ins as (
insert into key_phrase (body)
select body
from (values(:phrase)) d(body)
where not exists (select 1 from key_phrase where body = :phrase)
returning id
)
select id from ins
union all
select kp.id from key_phrase where body = :phrase
Not using on conflict will reduce the number of sequences that are burned. It should be highlighted, however, that there is no way to guarantee that serials will consistently be sequential. There could be gaps for other reasons. This is by design; the purpose of serials is to guarantee uniqueness, not "sequentiallity". If you really want an auto-increment with no holes, the consider row_number() and a view.
I didn't find a working solution for creating a "lookup column" in a Firebird database.
Here is an example:
Table1: Orders
[OrderID] [CustomerID] [CustomerName]
Table2: Customers
[ID] [Name]
When I run SELECT * FROM ORDERS I want to get OrderID, CustomerID and CustomerName....but CustomerName should automatically be computed by looking for the "CustomerID" in the "ID" column of "Customer" Table, returning the content of the "Name" column.
Firebird has calculated fields (generated always as/computed by), and these allow selecting from other tables (contrary to an earlier version of this answer, which stated that Firebird doesn't support this).
However, I suggest you use a view instead, as I think it performs better (haven't verified this, so I suggest you test this if performance is important).
Use a view
The common way would be to define a base table and an accompanying view that gathers the necessary data at query time. Instead of using the base table, people would query from the view.
create view order_with_customer
as
select orders.id, orders.customer_id, customer.name
from orders
inner join customer on customer.id = orders.customer_id;
Or you could just skip the view and use above join in your own queries.
Alternative: calculated fields
I label this as an alternative and not the main solution, as I think using a view would be the preferable solution.
To use calculated fields, you can use the following syntax (note the double parentheses around the query):
create table orders (
id integer generated by default as identity primary key,
customer_id integer not null references customer(id),
customer_name generated always as ((select name from customer where id = customer_id))
)
Updates to the customer table will be automatically reflected in the orders table.
As far as I'm aware, the performance of this option is less than when using a join (as used in the view example), but you might want to test that for yourself.
FB3+ with function
With Firebird 3, you can also create calculated fields using a trigger, this makes the expression itself shorter.
To do this, create a function that selects from the customer table:
create function lookup_customer_name(customer_id integer)
returns varchar(50)
as
begin
return (select name from customer where id = :customer_id);
end
And then create the table as:
create table orders (
id integer generated by default as identity primary key,
customer_id integer not null references customer(id),
customer_name generated always as (lookup_customer_name(customer_id))
);
Updates to the customer table will be automatically reflected in the orders table. This solution can be relatively slow when selecting a lot of records, as the function will be executed for each row individually, which is a lot less efficient than performing a join.
Alternative: use a trigger
However if you want to update the table at insert (or update) time with information from another table, you could use a trigger.
I'll be using Firebird 3 for my answer, but it should translate - with some minor differences - to earlier versions as well.
So assuming a table customer:
create table customer (
id integer generated by default as identity primary key,
name varchar(50) not null
);
with sample data:
insert into customer(name) values ('name1');
insert into customer(name) values ('name2');
And a table orders:
create table orders (
id integer generated by default as identity primary key,
customer_id integer not null references customer(id),
customer_name varchar(50) not null
)
You then define a trigger:
create trigger orders_bi_bu
active before insert or update
on orders
as
begin
new.customer_name = (select name from customer where id = new.customer_id);
end
Now when we use:
insert into orders(customer_id) values (1);
the result is:
id customer_id customer_name
1 1 name1
Update:
update orders set customer_id = 2 where id = 1;
Result:
id customer_id customer_name
1 2 name2
The downside of a trigger is that updating the name in the customer table will not automatically be reflected in the orders table. You would need to keep track of these dependencies yourself, and create an after update trigger on customer that updates the dependent records, which can lead to update/lock conflicts.
No need here a complex lookup field.
No need to add a persistant Field [CustomerName] on Table1.
As Gordon said, a simple Join is enough :
Select T1.OrderID, T2.ID, T2.Name
From Customers T2
Join Orders T1 On T1.IDOrder = T2.ID
That said, if you want to use lookup Fields (as we do it on a Dataset) with SQL you can use some thing like :
Select T1.OrderID, T2.ID,
( Select T3.YourLookupField From T3 where (T3.ID = T2.ID) )
From Customers T2 Join Orders T1 On T1.IDOrder = T2.ID
Regards.
I have a 2 databases that I want to merge with some similiar tables. The source tables have id as bigint and my destination table has int as ID. There aren't that many records in my source table (< 20k) so I want to assign new ids to all records so the ids can fit in an int. How can I do this with sql?
First Option
You can Use Sequence object as follow:
First Create a Sequence object and assign it's Start With value to max Id value in destination table plus 1. For example if max Id in destination table is 100, you need to assign 101 as Start With. You can also obtain the max Id value from destination table using a Max(Id) aggregate function and store it in a variable:
CREATE SEQUENCE SeqId
START WITH [Max value of Id in destination table]
INCREMENT BY 1 ;
GO
Then insert to destination table using following query:
Insert Into tblXXX (Id, ...) Values (NEXT VALUE FOR SeqId, ...)
Read more about Sequence Object
Second Option
You can make the destination table's Id column as Identity column with seed equal to destination table's Id column max value and Increment equal to 1.
Here is detailed example also Here
You did not provide much details so I can only provide a general guideline:
Note: Example assumes that you want to merge tables A and B into C and you want to generate new IDs. I also assume that these IDs are not referenced by other tables (foreign keys).
First you get record counts from tables A and B:
DECLARE #countA INT
DECLARE #countB INT
SET #countA = ( SELECT COUNT(*) FROM A )
SET #countB = ( SELECT COUNT(*) FROM B )
Next you use a window function to generate new IDs and insert records into table C.
INSERT INTO C
SELECT #countA + ROW_NUMBER() OVER( ORDER BY ID ) AS ID, ....
FROM A
INSERT INTO C
SELECT #countA + #countB + ROW_NUMBER() OVER( ORDER BY ID ) AS ID, ....
FROM B
I am trying to make stored procedure that:
- Get list of int rows
select ItemId from Items -- this returns: 1,2,3,4,5,6
In the second part of procedure I have to add row in another table for each of selected number. Something like:
foreach ItemId in previous result
insert into table (ItemIdInAnotherTable) values (ItemId)
UPDATE
I miss one important part from question.
In another part of procedure when I am inserting selected items in another table need to insert a few more columns. Something like this:
insert into dbo.ItemsNotificator
(UserId,ItemId)
(13879, (select ItemId from Items))
So it's not one column. Sorry for confusion :(
Edit :
Assuming that the table [table] already exists, and if User is a constant, then do like so:
INSERT INTO [table](UserId, ItemIdInAnotherTable)
SELECT 13879, ItemId
FROM Items;
If UserId comes from another table entirely, you'll need to figure out what relationship you need between UserId and ItemId. For instance, if all users are linked to all items, then it is:
INSERT INTO [table](UserId, ItemIdInAnotherTable)
SELECT u.UserId, i.ItemId
FROM Items i CROSS JOIN Users u;
If table [table] does NOT already exist, then you can use SELECT INTO, and specify a new table name (e.g. a #temp table stored in tempdb)
SELECT u.UserId, i.ItemId
INTO #tmpNewTable
FROM Items i CROSS JOIN Users u;
The columns in the newly created table will have the names UserId and ItemId and have the same types.
Looks simple to me:
INSERT INTO ItemIdInAnotherTable (ItemId)
SELECT ItemId from Items
That is exactly what a normal insert command does. Just do something like this:
insert into Table (ItemID)
select ItemID from Items;
use INSERT INTO..SELECT statement
INSERT INTO ItemIdInAnotherTable (ItemId)
SELECT ItemId
FROM Items