I'd like to add a unique key to column value but I must ignore rows that have the same values in columns value and header_id. For example, consider this table:
id | header_id | value
1 | 1 | a
2 | 1 | a
3 | 2 | a
So rows 1 and 2 point to same object and the unique key should accept them, but row 3 has a different header_id (pointing to another object) and, because it has the same value as object 1, it should violate unique constraint and raise an error.
Edit 16.2:1327:
I'm using a core framework that generates columns to handle history so I cannot normalize the table. My class has lots of columns but for this example I'm only considering the value column.
You could do it if you can change your table structure slightly:
your_table
id header_value
1 1
2 1
3 2
header_value
id header_id value
1 1 a
2 2 a
Add a foreign key constraint from your_table.header_value to header_value.id.
Now you can add a unique constraint on header_value.value.
You could use a trigger to simulate a unique constraint with your desired properties. Something like this would do the trick:
create or replace function sort_of_unique() returns trigger as $$
declare
got_one boolean;
begin
select exists(
select 1
from your_table
where header_id != new.header_id
and value = new.value
) into got_one;
if got_one then
raise exception 'Uniqueness violation in your_table';
end if;
return new;
end;
$$ language plpgsql;
create trigger sort_of_unique_trigger
before insert or update on your_table
for each row execute procedure sort_of_unique();
Then you'd get things like this happening:
=> insert into your_table (id, header_id, value) values (1, 1, 'a');
=> insert into your_table (id, header_id, value) values (2, 1, 'a');
=> insert into your_table (id, header_id, value) values (3, 2, 'a');
ERROR: Uniqueness violation in your_table
=> insert into your_table (id, header_id, value) values (3, 2, 'b');
=> update your_table set value = 'a' where id = 3;
ERROR: Uniqueness violation in your_table
You can create partial unique indexes by attaching a WHERE clause to the index. This allows you to apply your uniqueness constraint to slices of the table; however, I can't think of a way to get the WHERE clause to specify an "anti-slice" so I don't see a way to make this work with a partial index. I could be missing something obvious though.
After a while I found something. Using constrain CHECK with function to determine if exist (Cannot use SELECT in CHECK statement but you can use function with desired select)
CREATE OR REPLACE FUNCTION is_value_free(_header_id integer, _value varchar) RETURNS BOOLEAN AS
$$
BEGIN
RETURN NOT EXISTS (SELECT header_id,value FROM myschema.mytalbe WHERE value LIKE _value AND header_id != _header_id LIMIT 1);
END;
$$ LANGUAGE plpgsql;
ALTER TABLE mytable ADD CONSTRAINT uniq_value CHECK (is_value_free(header_id,value))
Related
I have a table
CREATE TABLE items(
id SERIAL PRIMARY KEY,
group_id INT NOT NULL,
item_id INT NOT NULL,
name TEXT,
.....
.....
);
I am creating a function that
takes set of row values for a single group_id, fail if multiple group_ids present in in input rows
compares it with matching values in the table (only for that group_id
updates changed values (only for the input group_id)
inserts new values
deletes table rows that are absent in the row input (compare rows with group_id and item_id)(only for the input group_id)
this is my function definition
CREATE OR REPLACE FUNCTION update_items(rows_input items[]) RETURNS boolean as $$
DECLARE
rows items[];
group_id_input integer;
BEGIN
-- get single group_id from input rows, fail if multiple group_id's present in input
-- read items of that group_id in table
-- compare input rows and table rows (of the same group_id)
-- create transaction
-- delete absent rows
-- upsert
-- return success of transaction (boolean)
END;
$$ LANGUAGE plpgsql;
I am trying to call the function in a query
select update_items(
(38,1,1283,"Name1"),
(39,1,1471,"Name2"),
(40,1,1333,"Name3")
);
I get the following error
Failed to run sql query: column "Name1" does not exist
I tried removing the id column values: that gives me the same error
What is the correct way to pass row values to a function that accepts table type array as arguments?
updates changed values
inserts new values deletes table rows that are
absent in the row input (compare rows with group_id and item_id)
If you want do upsert, you must upsert with unique constraint.
So there is two unique constraints. primary key(id), (group_id, item_id).
insert on conflict need consider these two unique constraint.
Since You want pass items[] type to the functions. So it also means that any id that is not in the input function arguments will also be deleted.
drop table if exists items cascade;
begin;
CREATE TABLE items(
id bigint GENERATED BY DEFAULT as identity PRIMARY KEY,
group_id INT NOT NULL,
item_id INT NOT NULL,
name TEXT
,unique(group_id,item_id)
);
insert into items values
(38,1,1283,'original_38'),
(39,1,1471,'original_39'),
(40,1,1333,'original_40'),
(42,1,1332,'original_42');
end;
main function:
CREATE OR REPLACE FUNCTION update_items (in_items items[])
RETURNS boolean
AS $FUNC$
DECLARE
iter items;
saved_ids bigint[];
BEGIN
saved_ids := (SELECT ARRAY (SELECT (unnest(in_items)).id));
DELETE FROM items
WHERE NOT (id = ANY (saved_ids));
FOREACH iter IN ARRAY in_items LOOP
INSERT INTO items
SELECT
iter.*
ON CONFLICT (id)
DO NOTHING;
INSERT INTO items
SELECT
iter.*
ON CONFLICT (group_id,
item_id)
DO UPDATE SET
name = EXCLUDED.name;
RAISE NOTICE 'rec.groupid: %, rec.items_id:%', iter.group_id, iter.item_id;
END LOOP;
RETURN TRUE;
END
$FUNC$
LANGUAGE plpgsql;
call it:
SELECT
*
FROM
update_items ('{"(38, 1, 1283, Name1) "," (39, 1, 1471, Name2) "," (40, 1, 1333, Name3)"}'::items[]);
references:
Iterating over integer[] in PL/pgSQL
How to match elements in an array of composite type?
IN vs ANY operator in PostgreSQL
Here's how I achieved UPSERT with DELETE missing rows, if anyone is looking to do the same.
CREATE OR REPLACE FUNCTION update_items(in_rows items[]) RETURNS INT AS $$
DECLARE
in_groups INTEGER[];
in_group_id INTEGER;
in_item_ids INTEGER[];
BEGIN
-- get single group id from input rows, fail if multiple group ids present in input
in_groups = (SELECT ARRAY (SELECT distinct(group_id) FROM UNNEST(in_rows)));
IF ARRAY_LENGTH(in_groups,1)>1 THEN
RAISE EXCEPTION 'Multiple group_ids found in input items: %', in_groups;
END IF;
in_group_id = in_groups[1];
-- delete items of this group that are absent in in_rows
in_item_ids := (SELECT ARRAY (SELECT (UNNEST(in_rows)).item_id));
DELETE FROM items
WHERE
master_code <> ANY (in_item_ids)
AND group_id = in_group_id;
-- upsert in_rows
INSERT INTO items
SELECT * FROM UNNEST(in_rows)
ON CONFLICT (group_id,item_d)
DO UPDATE SET
parent_group_id = EXCLUDED.parent_group_id,
mat_centre_id = EXCLUDED.mat_centre_id,
NAME = EXCLUDED.NAME,
opening_date = EXCLUDED.opening_date;
RETURN in_group_id;
-- return success of transaction (boolean)
END;
$$ LANGUAGE plpgsql;
This function removes rows that are missing from your in_rows
I have a table of 10 columns, and my INSERT statement only refers to specific columns in the table.
INSERT INTO SCHEMA.TABLE
(COL_1, COL_2)
VALUES
(VAL_1, VAL_2);
... or...
INSERT INTO SCHEMA.TABLE
(COL_1, COL_2)
SELECT VAL_1, VAL_2 FROM SCHEMA_2.TABLE_2;
However, when I execute it, the other columns are inserted always with a null value, instead of having the corresponding one depending on the column type (i.e. number). This is, if I have a numeric column, I should see a zero.
How can I do that insert properly?
*** Please consider I have no DDL privileges & I'm trying to insert into an existing table.
The easiest approach would probably to give your columns default values:
ALTER TABLE schema.table MODIFY (COL_1 NUMBER DEFAULT 0);
DEFAULT value it is; however, note that you have to pay attention to what you do because column might not get its default value. Here's an example:
SQL> create table test
2 (id number primary key,
3 name varchar2(10),
4 address varchar2(20) default 'Unknown', --> columns with default
5 num_val number default 0 --> values
6 );
Table created.
If you're inserting values without specifying column(s) that are supposed to get default values, everything will be as you'd want it to be:
SQL> insert into test (id, name) values (1, 'Little');
1 row created.
SQL> select * from test;
ID NAME ADDRESS NUM_VAL
---------- ---------- -------------------- ----------
1 Little Unknown 0
See? Both ADDRESS and NUM_VAL got default values.
However, if you mention those columns in INSERT statement, although setting them to NULL, they won't be set to their default values but NULL:
SQL> insert into test (id, name, address, num_val)
2 values (2, 'Foot', null, null);
1 row created.
SQL> select * from test;
ID NAME ADDRESS NUM_VAL
---------- ---------- -------------------- ----------
1 Little Unknown 0
2 Foot
As you can see, row with ID = 2 didn't get default values in ADDRESS and NUM_VAL columns.
Therefore, pay attention to what you do.
USE DEFAULT AS 0 for that column
or
use NVL( column_name, 0 ) --as per oracle syntax
--this would mean whenever theres null found for
-- that column set it to 0 (will work on insert)
or
Update column set column=0 where column IS NULL
--(will work after insert as the name suggests update)
Although frankly I don't recommend doing this, you can use a trigger to accomplish your goal:
CREATE OR REPLACE TRIGGER SCHEMA.TABLE_BI
BEFORE INSERT ON SCHEMA.TABLE
FOR EACH ROW
BEGIN
:NEW.COL_1 := COALESCE(:NEW.COL_1, 0); -- NUMBER column
:NEW.COL_2 := COALESCE(:NEW.COL_2, ' '); -- VARCHAR column
:NEW.COL_3 := COALESCE(:NEW.COL_3, SYSDATE); -- DATE column
END SCHEMA.TABLE_BI;
However, creating a trigger may require privileges you don't have.
To answer the question: that needs to be defined at table creation, determining default values. In this case, I wasn't able to do that because the table definition indicated NULL, even in the case of numbers.
Thanks anyway.
Suppose I have a table like this:
Number Product Type
1 Meat Cow
1 Milk A
If I insert a new row:
INSERT INTO t1 (Product, Type) VALUES (Meat, Cow)
I don't want a new row. I want the column "Number" where Product = Meat and Type = Cow be incremented by 1:
Number Product Type
2 Meat Cow
1 Milk A
Is there a SQL command to do this?
You may try the following by using ON CONFLICT that starts from version 9.5 :
create table t1( Number int,
Product varchar(15),
Type varchar(15),
primary key (Product, Type)
);
insert into t1(Number,Product,Type) values(1,'Meat','Cow');
insert into t1(Number,Product,Type) values(1,'Meat','Cow')
on conflict (Product,Type) do update set Number = t1.Number + 1;
select * from t1;
number product type
------ ------- ----
2 Meat Cow
Rextester Demo
where composite unique(primary) key is a must for Product and Type columns, if not exists than 42P10: there is no unique or exclusion constraint matching the ON CONFLICT specification error raises.
You can use triggers to achieve what you want. Format :
CREATE OR REPLACE TRIGGER trigger_name
INSTEAD OF INSERT ON table_name
WHEN (your_condition_here) --for example, row exist
BEGIN
UPDATE ... --your update query
END;
Create Unique Index on Product and Type, then
INSERT INTO t1 (Product, Type) VALUES (Meat, Cow)
ON CONFLICT ON CONSTRAINT <your_key>
UPDATE set Number = Number + 1
Should work.
I have a large number of rows that i want to insert simultaneously into a PostgreSQL database. I need to track what id is assigned for each row that is inserted. For example say we have the table:
CREATE TABLE example
(
id serial,
name text,
CONSTRAINT example_pkey PRIMARY KEY (id),
);
Now i have some data with ids that i dont want inserted (as the serial id column will assign a new id), but i need to keep track of the mapping between the old id and new id:
old id | name
-------------
-1 | foo
-2 | bar
-3 | baz
So i wrote this query
WITH data(oldid,name) AS ( VALUES
(-1,'foo'),
(-2,'bar'),
(-3,'baz')
)
INSERT INTO example(name)
SELECT name FROM data d
RETURNING id, d.oldid
Expecting to get something back like:
id | oldid
-----------
1 | -1
2 | -2
3 | -3
However this doesn't work, as i don't believe you can return a column that wasn't inserted. Is there any alternative way to do this?
I ended up creating a function that wrapped the inserting of a single row:
CREATE OR REPLACE FUNCTION add_example(
in_name text)
RETURNS integer AS
$BODY$
DECLARE
new_id integer;
BEGIN
INSERT INTO example(name)
VALUES (in_name) RETURNING id INTO new_id;
RETURN new_id;
END;
$BODY$
LANGUAGE plpgsql;
Then i can do:
WITH data(oldid, name) AS (VALUES
(-1,'foo'),
(-2,'bar'),
(-3,'baz')
)
SELECT oldid, add_example(name) AS id
FROM data
Which returns what i expect. I'd like to see if this can be done without the function though.
CREATE SEQUENCE data_id_seq;
CREATE TABLE DATA (
id integer default nextval('data_id_seq') NOT NULL PRIMARY KEY,
oldid integer,
name text,
);
INSERT INTO DATA(oldid,name) values (-1,'foo'),(-2,'bar'),(-3,'baz') returning id,oldid;
The optional RETURNING clause causes INSERT to compute and return
value(s) based on each row actually inserted
from https://www.postgresql.org/docs/current/static/sql-insert.html
so column parasite is unavoidable for such solution:
alter table example add column old bigint;
WITH d(oldid,name) AS ( VALUES
(-1,'foo'),
(-2,'bar'),
(-3,'baz')
)
INSERT INTO example(name,old)
SELECT "name", oldid FROM d
RETURNING id, old
How to insert a number into the table, only if the table does not already have that number in it?
I am looking for specific SQL code, not really sure how to approach this. Tried several things, nothing's working.
EDIT
Table looks like this:
PK ID Value
1 4 500
2 9 3
So if I am trying to INSERT (ID, Value) VALUES (4,100) it should not try to do it!
If ID is supposed to be unique, there should be a unique constraint defined on the table. That will throw an error if you try to insert a value that already exists
ALTER TABLE table_name
ADD CONSTRAINT uk_id UNIQUE( id );
You can catch the error and do whatever you'd like if an attempt is made to insert a duplicate key-- anything from ignoring the error to logging and re-raising the exception to raising a custom exception
BEGIN
INSERT INTO table_name( id, value )
VALUES( 4, 100 );
EXCEPTION
WHEN dup_val_on_index
THEN
<<do something>>
END;
You can also code the INSERT so that it inserts 0 rows (you would still want the unique constraint in place both from a data model standpoint and because it gives the optimizer more information and may make future queries more efficient)
INSERT INTO table_name( id, value )
SELECT 4, 100
FROM dual
WHERE NOT EXISTS(
SELECT 1
FROM table_name
WHERE id = 4 )
Or you could code a MERGE instead so that you update the VALUE column from 500 to 100 rather than inserting a new row.
Try MERGE statement:
MERGE INTO tbl USING
(SELECT 4 id, 100 value FROM dual) data
ON (data.id = tbl.id)
WHEN NOT MATCHED THEN
INSERT (id, value) VALUES (data.id, data.value)
INSERT INTO YOUR_TABLE (YOUR_FIELD)
SELECT '1' FROM YOUR_TABLE YT WHERE YT.YOUR_FIELD <> '1' LIMIT 1
Of course, that '1' will be your number or your variable.
You can use INSERT + SELECT to solve this problem.