I want to insert a data from parent table to child table if it isn't already in the child table.
create table parents(
c1 varchar (100) primary key,
c2 varchar (100),
);
CREATE TABLE child
(
c1 varchar (100) PRIMARY KEY,
c3 varchar (100),
FOREIGN KEY (c1) REFERENCES parents(c1)
);
Assuming, by data, you mean column c1 only, you can insert into child using a select from parent where you can filter the row to those which aren't present in the child table.
insert into child (c1, c3)
select c1, c2
from parents
where c1 not in (
select c1 from child
);
Related
I have a situation with two tables where one has a foreign key pointing to the other table (simplified) schema:
CREATE TABLE table1 (
name VARCHAR(64) NOT NULL,
PRIMARY KEY(name)
);
CREATE TABLE table2 (
id SERIAL PRIMARY KEY,
table1_name VARCHAR(64) NOT NULL REFERENCES table1(name)
);
Now I regret using the name column as primary key in table1 - and would like to add integer serial key instead. Since I already have data in the database I guess I need to do this carefully. My current plan is as follows:
Drop the foreign key constraint: table2(name) with ALTER TABLE table2 DROP CONSTRAINT table2_table1_name_fkey;
Drop the primary key constraint on table1(name) with ALTER TABLE table1 DROP CONSTRAINT name_pkey;.
Add a unique constraint on table1(name) with ALTER TABLE table1 ADD UNIQUE(name);
Add a automatic primary key to table1 with ALTER TABLE table1 ADD COLUMN ID SERIAL PRIMARY KEY;.
Add a new column table1_id to table2 with ALTER TABLE table2 ADD COLUMN table1_id INT;
Update all rows in table2 - so that the new column (which will be promoted to a foreign key) gets the correct value - as inferred by the previous (still present) foreign key table1_name.
I have completed steps up to an including step 5, but the UPDATE (with JOIN?) required to complete 6 is beyond my SQL paygrade. My current (google based ...) attempt looks like:
UPDATE
table2
SET
table2.table1_id = t1.id
FROM
table1 t1
LEFT JOIN table2 t2
ON t2.table1_name = t1.name;
You do not need JOIN in UPDATE.
UPDATE
table2 t2
SET
table1_id = t1.id
FROM
table1 t1
WHERE
t2.table1_name = t1.name;
I have some numbers of tables with foreign key between them. Structure of table is not important. For example, table A is a top level table. Table B and C have foreign key on table A and tables D, E and F and G have foreign key on table B and C resp.
The question is: is there a way for clone one of row from table A
with all depeddencies (row in tables B - G) using SQL?
You didn't provide structure nor data, so you will have to work with my example. The basic idea is just selecting the appropriate FK columns to the respective PK columns as you progress from parent to child.
-- create base tables
create table a (a_id integer, a_col1 text, constraint a_pk primary key (a_id));
create table b (b_id integer, a_id integer, b_col1 text
, constraint b_pk primary key (b_id)
, constraint b_fk_a foreign key (a_id)
references a(a_id)
);
create table g (g_id integer, b_id integer, g_col1 text
, constraint g_pk primary key (g_id)
, constraint g_fk_b foreign key (b_id)
references b(b_id)
);
-------------------------------------------------------------------------------------------------------
-- populate
insert into a (a_id,a_col1) values (11,'ta1'), (12,'ta2');
insert into b (b_id,a_id,b_col1) values (21,11,'tb1'), (22,11,'tb2'), (23,12,'tb3'), (24,12,'tb4');
insert into g (g_id,b_id,g_col1) values (71,21,'tg1'), (72,21,'tg2'), (73,22,'tg3'), (74,22,'tg4')
, (75,23,'tg5'), (76,23,'tg6'), (77,24,'tg7'), (78,24,'tg8');
-------------------------------------------------------------------------------------------------------
-- Soution: clone a_id 12
create table a_clone as
select *
from a
where a_id = 12;
create table b_clone as
select *
from b
where a_id = 12;
create table g_clone as
select *
from g
where b_id in
(select b_id
from b
where a_id = 12
);
-- done
The 'comes to mind' suggestion from Sticky Bit is doable, but it's not straight forward. I believe the above it straight forward.
I'm trying to use the performance of COPY FROM command in PostgreSQL to get all data of 1 table of a CSV file (CSV -> table1) and I need to insert other data, but, in a new table. I will need of a primary key of first table to put as a foreign key in second table.
Example:
I need to insert 1,000,000 of names in table1 and 500,000 of names in table2, but, all names in table2 reference to 1 tuple in table1.
CREATE TABLE table1 (
table1Id bigserial NOT NULL,
Name varchar(100) NULL,
CONSTRAINT table1Id PRIMARY KEY (table1Id)
);
CREATE TABLE table2 (
table2Id bigserial NOT NULL,
Other_name varchar(100) NOT NULL
table1_table1Id int8 NOT NULL,
CONSTRAINT table2_pk PRIMARY KEY (table2Id)
);
Command COPY does not allow table manipulations while copying data (such as look up to other table for fetching proper foreign keys to insert). To insert into table2 ids for corresponding rows from table1 you need to drop NOT NULL constraint for that field, COPY data and then UPDATE that fields separately.
Assuming table1 and table2 tables can be joined by table1.Name = table2.Other_name, the code is:
Before COPY:
ALTER TABLE table2 ALTER COLUMN table1_table1Id DROP NOT NULL;
After COPY:
UPDATE table2 SET table2.table1_table1Id = table1.table1Id
FROM table1
WHERE table1.Name = table2.Other_name;
ALTER TABLE table2 ALTER COLUMN table1_table1Id SET NOT NULL;
There is this field in a table:
room_id INT NOT NULL CONSTRAINT room_id_ref_room REFERENCES room
I have three 2 tables for two kinds of rooms: standard_room and family_room
How to do something like this:
room_id INT NOT NULL CONSTRAINT room_id_ref_room REFERENCES standard_room or family_room
I mean, room_id should reference either standard_room or family_room.
Is it possible to do so?
Here is the pattern I've been using.
CREATE TABLE room (
room_id serial primary key,
room_type VARCHAR not null,
CHECK CONSTRAINT room_type in ("standard_room","family_room"),
UNIQUE (room_id, room_type)
);
CREATE_TABLE standard_room (
room_id integer primary key,
room_type VARCHAR not null default "standard_room",
FOREIGN KEY (room_id, room_type) REFERENCES room (room_id, room_type),
CHECK CONSTRAINT room_type = "standard_room"
);
CREATE_TABLE family_room (
room_id integer primary key,
room_type VARCHAR not null default "family_room",
FOREIGN KEY (room_id, room_type) REFERENCES room (room_id, room_type),
CHECK CONSTRAINT room_type = "family_room"
);
That is, the 'subclasses' point at the super-class, by way of a type descriminator column (such that the pointed to base class is of the correct type, and that primary key of the super class is the same as the child classes.
Here's the same SQL from the accepted answer that works for PostGres 12.8. There's a few issues not only the CREATE_TABLE syntax mistake:
CREATE TABLE room (
room_id serial primary key,
room_type VARCHAR not null,
CONSTRAINT room_in_scope CHECK (room_type in ('standard_room','family_room')),
CONSTRAINT unique_room_type_combo UNIQUE (room_id, room_type)
);
CREATE TABLE standard_room (
room_id integer primary key,
room_type VARCHAR not null default 'standard_room',
CONSTRAINT roomid_std_roomtype_fk FOREIGN KEY (room_id, room_type) REFERENCES public."room" (room_id, room_type),
CONSTRAINT std_room_constraint CHECK (room_type = 'standard_room')
);
CREATE TABLE family_room (
room_id integer primary key,
room_type VARCHAR not null default 'family_room',
CONSTRAINT roomid_fam_roomtype_fk FOREIGN KEY (room_id, room_type) REFERENCES "room" (room_id, room_type),
CONSTRAINT fam_room_constraint CHECK (room_type = 'family_room')
);
NOTE: The SQL above uses constraints to enforce the child room_type values default to the parent tables' room_type values: 'standard_room' or 'family_room'.
PROBLEM: Since the child tables Primary Key's expect either the standard and family room Primary Key that means you can't insert more than one record in thsee two child tables.
insert into room (room_type) VALUES ('standard_room'); //Works
insert into room (room_type) values ('family_room'); //Works
insert into standard_room (room_id,pictureAttachment) VALUES (1,'Before Paint'); //Works
insert into standard_room (room_id,pictureAttachment) VALUES (1,'After Paint'); //Fails
insert into standard_room (room_id,pictureAttachment) VALUES (1,'With Furniture');
insert into family_room (room_id,pictureAttachment) VALUES (2, 'Beofre Kids'); //Works
insert into family_room (room_id,pictureAttachment) VALUES (2,'With Kids'); //Fails
To make the tables accept > 1 row you have to remove the Primary Keys from the 'standard_room' and 'family_room' tables which is BAD database design.
Despite 26 upvotes I will ping OP about this as I can see the answer was typed free hand.
Alternate Solutions
For smallish tables with less than a handful of variations a simple alterative is a single table with Bool columns for different table Primary Key fields.
Single Table "Room"
Id
IsStandardRoom
IsFamilyRoom
Desc
Dimensions
1
True
False
Double Bed, BIR
3 x 4
2
False
True
3 Set Lounge
5.5 x 7
SELECT * FROM Room WHERE IsStdRoom = true;
At the end of the day, in a relational database it's not very common to be adding Room Types when it involves creating the necessary related database tables using DDL commands (CREATE, ALTER, DROP).
A typical future proof database design allowing for more Tables would look something like this:
Multi Many-To-Many Table "Room"
Id
TableName
TableId
1
Std
8544
2
Fam
236
3
Std
4351
Either Standard or Family:
select * from standard_room sr where sr.room_id in
(select TableId from room where TableName = 'Std');
select * from family_room fr where fr.room_id in
(select id from room where TableName = 'Fam');
Or both:
select * from standard_room sr where sr.room_id in
(select TableId from room where TableName = 'Std')
UNION
select * from family_room fr where fr.room_id in
(select id from room where TableName = 'Fam');
Sample SQL to demo Polymorphic fields:
If you want to have different Data Types in the polymorphic foreign key fields then you can use this solution. Table r1 stores a TEXT column, r2 stores a TEXT[] Array column and r3 a POLYGON column:
CREATE OR REPLACE FUNCTION null_zero(anyelement)
RETURNS INTEGER
LANGUAGE SQL
AS $$
SELECT CASE WHEN $1 IS NULL THEN 0 ELSE 1 END;
$$;
CREATE TABLE r1 (
r1_id SERIAL PRIMARY KEY
, r1_text TEXT
);
INSERT INTO r1 (r1_text)
VALUES ('foo bar'); --TEXT
CREATE TABLE r2 (
r2_id SERIAL PRIMARY KEY
, r2_text_array TEXT[]
);
INSERT INTO r2 (r2_text_array)
VALUES ('{"baz","blurf"}'); --TEXT[] ARRAY
CREATE TABLE r3 (
r3_id SERIAL PRIMARY KEY
, r3_poly POLYGON
);
INSERT INTO r3 (r3_poly)
VALUES ( '((1,2),(3,4),(5,6),(7,8))' ); --POLYGON
CREATE TABLE flex_key_shadow (
flex_key_shadow_id SERIAL PRIMARY KEY
, r1_id INTEGER REFERENCES r1(r1_id)
, r2_id INTEGER REFERENCES r2(r2_id)
, r3_id INTEGER REFERENCES r3(r3_id)
);
ALTER TABLE flex_key_shadow ADD CONSTRAINT only_one_r
CHECK(
null_zero(r1_id)
+ null_zero(r2_id)
+ null_zero(r3_id)
= 1)
;
CREATE VIEW flex_key AS
SELECT
flex_key_shadow_id as Id
, CASE
WHEN r1_id IS NOT NULL THEN 'r1'
WHEN r2_id IS NOT NULL THEN 'r2'
WHEN r3_id IS NOT NULL THEN 'r3'
ELSE 'wtf?!?'
END AS "TableName"
, CASE
WHEN r1_id IS NOT NULL THEN r1_id
WHEN r2_id IS NOT NULL THEN r2_id
WHEN r3_id IS NOT NULL THEN r3_id
ELSE NULL
END AS "TableId"
FROM flex_key_shadow
;
INSERT INTO public.flex_key_shadow (r1_id,r2_id,r3_id) VALUES
(1,NULL,NULL),
(NULL,1,NULL),
(NULL,NULL,1);
SELECT * FROM flex_key;
I have two tables with 1...0.n relation:
--drop table if exists child;
--drop table if exists master;
create table master (
master_id serial primary key,
master_name varchar,
constraint unique_master unique (master_name)
);
create table child (
child_id serial primary key,
master_id integer references master (master_id),
child_name varchar
);
In master table I have two rows:
insert into master (master_name) values ('master01');
insert into master (master_name) values ('master02');
SQLFiddle
Now I need to add some related rows for master01 into child table. I have only string master01 as input, not master_id. I have a solution using cross join:
insert into child (master_id, child_name)
select
master_id, child_name
from
(select master_id from master where master_name = 'master01') as master_data
cross join (
values
('child01'),
('child02'),
('child03')
) child_data (child_name);
This works, but I feel like there should be something easier. What other options I have?
Without the cross join
insert into child (master_id, child_name)
select
(select master_id from master where master_name = 'master01'),
child_name
from (values
('child01'),
('child02'),
('child03')
) child_data (child_name)
I ended up using pgScript:
SET #MN = select master_id from master where master_name = 'master01';
insert into child (master_id, child_name) values
(#MN, 'child01'),
(#MN, 'child02'),
(#MN, 'child03')