I have 2 tables in Postgres
main
entity
id
id
name
name
main_id
I need to generate id for entity, get name and id from main and insert into entity table
INSERT INTO entity (select uuid_generate_v4(), name, main_id)
SELECT name, id FROM main
But I get this error
ERROR: syntax error at or near "SELECT"
I know that the point is that I am inserting more arguments than I receive, but I do not know how to proceed further
The first pair of parentheses define the target columns of the INSERT statement. You need to move the UUID generation to the SELECT part:
INSERT INTO entity (id, name, main_id)
SELECT uuid_generate_v4(), name, id
FROM main
Related
So I've been going through SQL migrations to insert data in a SEQUENTIAL manner specifically from parent to child.
I've inserted data in the parent table. Now I've to store the primary key value of that
specific row (WHERE condition is defined in query for reference " where description = '1234'") in a variable.
And while inserting data to the child table I've to use that primary key value stored in a variable in place of a foreign key column("country_code_id") of the child table.
I'm using Postgresql
CREATE TABLE Countries
(
id SERIAL,
description VARCHAR(100),
CONSTRAINT coutry_pkey PRIMARY KEY (id)
);
CREATE TABLE Cities
(
country_code_id int ,
city_id int,
description VARCHAR(100),
CONSTRAINT cities_pkey PRIMARY KEY (city_id),
CONSTRAINT fk_cities_countries FOREIGN KEY (country_code_id) REFERENCES Countries (id)
);
INSERT INTO COUNTRIES (description) VALUES('asdf');
#countrid = SELECT id FROM COUNTRIES WHERE description = 'asdf';
INSERT INTO cities VALUES (countrid, 1 , 'abc');
SQL does not have variables. The normal way to do this is to use INSERT ... RETURNING:
INSERT INTO countries (description) VALUES ('1234')
RETURNING id;
This will return the automatically generated primary key. You store that in a variable on the client side and run a second statement:
INSERT INTO cities (country_code_id, city_id, description)
VALUES (4711, 1, 'abc');
where 4711 is the value returned from the first statement. To avoid hard-coding the value, you can use a prepared statement, which also will boost performance.
An alternative, more complicated, solution is to run both statements in a single statement using a common table expression:
WITH country_ids AS (
INSERT INTO countries (description) VALUES ('1234')
RETURNING id
INSERT INTO (country_code_id, city_id, description)
SELECT id, 1, 'abc'
FROM country_ids;
Consider the following schema:
CREATE TABLE IF NOT EXISTS snippet_types (
id INTEGER NOT NULL PRIMARY KEY,
name TEXT NOT NULL UNIQUE
);
CREATE TABLE IF NOT EXISTS snippets (
id INTEGER NOT NULL PRIMARY KEY,
title TEXT,
content TEXT,
type INTEGER NOT NULL,
FOREIGN KEY(type) REFERENCES snippet_types(id)
);
This schema assumes a one-to-many relationship between tables and allows efficiently maintaining a set of ENUMs in the snippet_types table. Efficiency comes from the fact that we don't need to store the whole string describing snippet type in the snippets table, but this decision also leads us to some inconvenience: upon inserting we need to retrieve snippet id from snippet_types and this leads to one more select and check before inserting:
SELECT id FROM snippet_types WHERE name = "foo";
-- ...check that > 0 rows returned...
INSERT INTO snippets (title, content, type) values ("bar", "buz", id);
We could also combine this insert and select into one select like that:
INSERT INTO snippets (title, content, type)
SELECT ("bar", "buz", id) FROM snippet_types WHERE name = "foo"
However, if "foo" type is missing in snippet_types then 0 rows would have been inserted and no error returned and I don't see a possibility to get a number of rows sqlite actually inserted.
How can I insert ENUM-containing tuple in one query?
I'm running the following SQLite workaround to add a primary key to a table that did not have one. I am getting a datatype mismatch on
INSERT INTO cities
SELECT id, name FROM old_cities;
However, the fields have exactly the same type. Is it possible that his happens due to running the queries from DbBrowser for SQLite?
CREATE table cities (
id INTEGER NOT NULL,
name TEXT NOT NULL
);
INSERT INTO cities (id, name)
VALUES ('pan', 'doul');
END TRANSACTION;
PRAGMA foreign_keys=off;
BEGIN TRANSACTION;
ALTER TABLE cities RENAME TO old_cities;
--CREATE TABLE cities (
-- id INTEGER NOT NULL PRIMARY KEY,
-- name TEXT NOT NULL
--);
CREATE TABLE cities (
id INTEGER NOT NULL,
name TEXT NOT NULL,
PRIMARY KEY (id)
);
SELECT * FROM old_cities;
INSERT INTO cities
SELECT id, name FROM old_cities;
DROP TABLE old_cities;
COMMIT;
You have defined the column id of the table cities to be INTEGER, but with this:
INSERT INTO cities (id, name) VALUES ('pan', 'doul');
you insert the string 'pan' as id.
SQLite does not do any type checking in this case and allows it.
Did you mean to insert 2 rows each having the names 'pan' and 'doul'?
If so, you should do something like:
INSERT INTO cities (id, name) VALUES (1, 'pan'), (2, 'doul');
Later you rename the table cities to old_cities and you recreate cities but you do something different: you define id as INTEGER and PRIMARY KEY.
This definition is the only one that forces type checking in SQLite.
So, when you try to insert the rows from old_cities to cities you get an error because 'pan' is not allowed in the column id as it is defined now.
In Postgres, is there a way to atomically insert a row into a table, where one column references another table, and we look up to see if the desired row exists in the referenced table and inserts it as well if it is not?
For example, say we have a US states table and a cities table which references the states table:
CREATE TABLE states (
state_id serial primary key,
name text
);
CREATE TABLE cities (
city_id serial,
name text,
state_id int references states(state_id)
);
When I want to add the city of Austin, Texas, I want to be able to see whether Texas exists in the states table, and if so use its state_id in the new row I'm inserting in the cities table. If Texas doesn't exist in the states table, I want to create it and then use its id in the cities table.
I tried this query, but I got an error saying
ERROR: WITH clause containing a data-modifying statement must be at the top level
LINE 2: WITH inserted AS (
^
WITH state_id AS (
WITH inserted AS (
INSERT INTO states(name)
VALUES ('Texas')
ON CONFLICT DO NOTHING
RETURNING state_id),
already_there AS (
SELECT state_id FROM states
WHERE name='Texas')
SELECT * FROM inserted
UNION
SELECT * FROM already_there)
INSERT INTO cities(name, state_id)
VALUES
('Austin', (SELECT state_id FROM state_id));
Am I overlooking a simple solution?
Here is one option:
with inserted as (
insert into states(name) values ('Texas')
on conflict do nothing
returning state_id
)
insert into cities(name, state_id)
values (
'Dallas',
coalesce(
(select state_id from inserted),
(select state_id from states where name = 'Texas')
)
);
The idea is to attempt to insert in a CTE, and then, in the main insert, check if a value was inserted, else select it.
For this to work properly, you need a unique constraint on states(name):
create table states (
state_id serial primary key,
name text unique
);
Demo on DB Fiddlde
You can force the insert statement to return a value:
WITH inserted AS (
INSERT INTO states (name)
VALUES ('Texas')
ON CONFLICT (name) DO UPDATE SET name = EXCLUDED.NAME
RETURNING state_id
)
. . .
The DO UPDATE SET forces the INSERT to return something.
I notice that you don't have a unique constraint, so you also need that:
ALTER TABLE states ADD CONSTRAINT unq_state_name
UNIQUE (name);
Otherwise the ON CONFLICT doesn't have anything to work with.
I have the following table:
CREATE TABLE group_members(id integer primary key AUTOINCREMENT, group_id integer, member_id integer, FOREIGN KEY (member_id) REFERENCES users(id));
I'm trying to insert a record into the group_members table by selecting the value for group_id from the user table, and then passing in a value for the member_id.
insert into group_members (group_id, member_id)
values (select id from users where code ='12345' and location='multiple', 281);
Where 281 is the member id I'm trying to pass in.
But I'm getting the following error message:
Error: near "select": syntax error
Can you point me in the right direction?
Subqueries must be written in parentheses. The parentheses in your queries already belong to the VALUES clause, so you need another pair:
INSERT INTO group_members (group_id, member_id)
VALUES ((SELECT id FROM users WHERE code ='12345' AND location='multiple'), 281);
Alternatively, use the other form of the INSERT statement that uses a query instead of the VALUES clause:
INSERT INTO group_members (group_id, member_id)
SELECT id, 281 FROM users WHERE code ='12345' AND location='multiple';