I want my ID to be autogenerated and want a format like this:
12-0001, 12-0002
12 represent the year 2012 which is the current year of the system date.
And my last record for ID is 12-0999 and when 2013 comes I want my ID to change the year prefix and reset the 4 digit like this:
13-0001, 13-0002.
I'm using asp.net mvc 3 and sql server express 2008.
Can anyone tell me of a way I can do this.
I see two options:
(1) if your table that you're inserting data into has a DATE or DATETIME column that has the "right" year in it, you could simply add a persisted, computed column to your table - something like:
ALTER TABLE dbo.YourTable
ADD PKID AS RIGHT(CAST(YEAR(DateColumn) AS CHAR(4)), 2) + '-' +
RIGHT('00000' + CAST(ID AS VARCHAR(5)), 5) PERSISTED
Assuming that ID is an INT IDENTITY column that autogenerates sequential numbers, and you want to call your new column PKID (change as needed).
Since this is a persisted computed column, it's computed once - when the row is inserted - and it can be indexed and used as primary key.
(2) If you don't have anything like a date column in your table, then the only option would be to have a AFTER INSERT trigger on that table that does something like this (again: assuming you have a column ID INT IDENTITY to provide the auto-incremented numbers):
CREATE TRIGGER trgInsert ON dbo.YourTable
AFTER INSERT
AS
BEGIN
DECLARE #YearPrefix CHAR(2)
SET #YearPrefix = RIGHT(CAST(YEAR(GETDATE()) AS CHAR(4)), 2)
UPDATE dbo.YourTable
SET OtherID = #YearPrefix + '-' + RIGHT('00000' + CAST(i.EmployeeID AS VARCHAR(5)), 5)
FROM INSERTED i
WHERE dbo.YourTable.EmployeeID = i.EmployeeID
END
And of course, first you need to add this new PKID column to your table, too, so that the trigger can store values in it :-)
ALTER TABLE dbo.YourTable
ADD PKID VARCHAR(10) NOT NULL DEFAULT ('X') -- needs to be NOT NULL for Primary Key
Related
Table: test_seq
id (varchar(8))
raw_data (text)
cd_1
'I'm text'
cd_2
'I'm more text'
CREATE SEQUENCE cd_seq CYCLE START 1 MAXVALUE 2;
ALTER TABLE test_seq
ALTER COLUMN id SET DEFAULT ('cd_'||nextval('cd_seq'))::VARCHAR(8);
UPDATE test_seq
SET raw_data = 'New Text'
WHERE "id" = 'cd_'||nextval('cd_seq')::VARCHAR(8);
I am making a table that will store raw data as a short term backup, if for some reason the data ingestion fails and we need to go back without extracting it again. I'm trying to setup a way to have the records get replace when we have reached the ID limit.
So if I want 25 records in the table, when the SEQUENCE rolls back from the maximum ('cd_25') to ('cd_1'), I want raw_data to get updated to the new data.
I've come up with the SEQUENCE and the DEFAULT value for the first inserts but my UPDATE command won't update the records even when the "id" matches the 'cd_'||nextval('cd_seq') and it will sometimes UPDATE 9 rows at once.
I checked the values of "id" and 'cd_'||nextval('cd_seq') and they appear to be a match but the WHERE doesn't work properly.
Am I missing something or am I overcomplicating things?
Thank you
While I agree with Adrian Klaver's comments that this approach is pretty fragile due to how sequences work, if:
You can make sure the column default value is the only call to the sequence
You don't mind skipped rows if an insert fails, but sequence still increments its value
You can make sure all inserts handle conflicts like below
this can work.
Instead of trying to insert data by updating existing rows - which by the way forces you to prepopulate the table - just actually insert it and handle the conflict.
insert into test_seq
(text_column)
values
('e')
on conflict(id) do update set text_column=excluded.text_column;
This also lets you insert more than one row at once (up to the max size of your table, the length of your sequence), compared to your current update approach, as I do in the test below.
drop sequence if exists cd_seq cascade;
create sequence cd_seq cycle start 1 maxvalue 4;
drop table if exists test_seq cascade;
create table test_seq
(id text primary key default ('cd_'||nextval('cd_seq'))::VARCHAR(8),
text_column text);
insert into test_seq
(text_column)
values
('a'),
('b'),
('c'),
('d')
on conflict(id) do update set text_column=excluded.text_column;
select id, text_column from test_seq;
-- id | text_column
--------+-------------
-- cd_1 | a
-- cd_2 | b
-- cd_3 | c
-- cd_4 | d
--(4 rows)
insert into test_seq
(text_column)
values
('e'),
('f')
on conflict(id) do update set text_column=excluded.text_column;
select id, text_column from test_seq;
-- id | text_column
--------+-------------
-- cd_3 | c
-- cd_4 | d
-- cd_1 | e
-- cd_2 | f
--(4 rows)
If you try to insert more rows than the length of your sequence, you'll get
ERROR: ON CONFLICT DO UPDATE command cannot affect row a second time
HINT: Ensure that no rows proposed for insertion within the same
command have duplicate constrained values.
If in your current solution you gave your update a source table to get multiple rows from and their number also exceeded the sequence length, it wouldn't pose a problem - in conflicting pairs you'd just get the last one. Here's your update, fixed (but still requires that your table is pre-populated):
with new as (
select ('cd_'||nextval('cd_seq'))::VARCHAR(8) id,'g' text_column union all
select ('cd_'||nextval('cd_seq'))::VARCHAR(8) id,'h' text_column union all
select ('cd_'||nextval('cd_seq'))::VARCHAR(8) id,'i' text_column union all
select ('cd_'||nextval('cd_seq'))::VARCHAR(8) id,'j' text_column union all
select ('cd_'||nextval('cd_seq'))::VARCHAR(8) id,'k' text_column)
update test_seq old
set text_column=new.text_column
from new
where old.id=new.id;
Background:
I am making a db for a reservartions calendar. The reservations are hourly based, so I need to insert many items to one column called "hours_reserved".
Example tables of what I need:
Table "Space"
Column / Values
id / 1
date / 5.2.2020
hours / { 8-10, 10-12 }
Table "reservation"
Column / Values
id / 1
space_id / 1
date / 5.2.2020
reserved_hours / 8-10
Table "reservation"
Column / Values
id / 2
space_id / 1
date / 5.2.2020
hours / 10-12
So I need to have multiple items inserted into "space" table "hours" column.
How do I do this in Postgres?
Also is there a better way to accomplish this?
There is more way to do this, depending on the type of the hours field (i.e. text[], json or jsonb) I'd go with jsonb just because you can do a lot of things with it and you'll find this experience to be useful in the short term.
CREATE TABLE "public"."space"
("id" SERIAL, "date_schedule" date, "hours" jsonb, PRIMARY KEY ("id"))
Whenever you insert a record in this table that's manually crafted, write it as text (single quoted json object) and cast it to jsonb
insert into "space"
(date_schedule,hours)
values
('05-02-2020'::date, '["8-10", "10-12"]'::jsonb);
There is more than one way to match these available hours against the reservations and you can take a look at the docs, on the json and jsonb operations. For example, doing:
SELECT id,date_schedule, jsonb_array_elements(hours) hours FROM "public"."space"
would yield
Which has these ugly double quotes (which is correct, since json can hold several kinds of scalars, that column is polimorfic :D)
However, you can perform a little transformation to remove them and be able to perform a join with reservations
with unnested as (
SELECT id,date_schedule, jsonb_array_elements(hours) hours FROM "public"."space"
)
select id,date_schedule,replace(hours::text, '"','') from unnested
The same can be achieved defining the field as text[] (the insertion syntax is different but trivial)
in that scenario your data will look like:
Which you can unwrap as:
SELECT id,date_schedule, unnest(hours) FROM "public"."space"
Apparently
ALTER TABLE mytable
ADD COLUMN myarray text[];
Works fine.
I got a following problem when trying to put(update) into that column using postman(create works fine):
{
"myarray": ["8-10"]
}
Results into:
"message": "error: invalid input syntax for type integer:
\"{\"myarray\":[\"8-10\"]}\""
I have two tables, stuff and nonsense.
create table stuff(
id serial primary key,
details varchar,
data varchar,
more varchar
);
create table nonsense (
id serial primary key,
data varchar,
more varchar
);
insert into stuff(details) values
('one'),('two'),('three'),('four'),('five'),('six');
insert into nonsense(data,more) values
('apple','accordion'),('banana','banjo'),('cherry','cor anglais');
See http://sqlfiddle.com/#!17/313fb/1
I would like to copy random values from nonsense to stuff. I can do this for a single value using the answer to my previous question: SQL Server Copy Random data from one table to another:
update stuff
set data=(select data from nonsense where stuff.id=stuff.id
order by random() limit 1);
However, I would like to copy more than one value (data and more) from the same row, and the sub query won’t let me do that, of course.
I Microsoft SQL, I can use the following:
update stuff
set data=sq.town,more=sq.state
from stuff s outer apply
(select top 1 * from nonsense where s.id=s.id order by newid()) sq
I have read that PostGresql uses something like LEFT JOIN LATERAL instead of OUTER APPPLY, but simply substituting doesn’t work for me.
How can I update with multiple values from a random row of another table?
As of Postgres 9.5, you can assign multiple columns from a subquery:
update stuff
set (data, more) = (
select data, more
from nonsense
where stuff.id=stuff.id
order by random()
limit 1
);
I created a table which have following columns.
E_id, e_name,e_date,time_in,time_out
I want autoupdate e_date,time_in and time_out column when i insert new values in table.
You can define default values for your columns.
Which values do you need?
For example, if you need the Sysdate:
CREATE TABLE t
(...,
INSERT_DATE DATE DEFAULT SYSDATE NOT NULL);
or, if you need to update your table structure:
ALTER TABLE t
MODIFY (INSERT_DATE DATE DEFAULT SYSDATE);
You can use SYSTIMESTAMP too, instead of SYSDATE, if you need fractional seconds.
But if you have character fields you can use something like the following:
DEFAULT TO_CHAR(SYSDATE, 'YYYYMMDD') -- Date component
or
DEFAULT TO_CHAR(SYSDATE, 'HH24MISS') -- Time component
After running for a long time, I get more and more holes in the id field. Some tables' id are int32, and the id sequence is reaching its maximum value. Some of the Java sources are read-only, so I cannot simply change the id column type from int32 to long, which would break the API.
I'd like to renumber them all. This may be not good practice, but good or bad is not concerned in this question. I want to renumber, especially, those very long IDs like "61789238", "548273826529524324". I don't know why they are so long, but shorter IDs are also easier to handle manually.
But it's not easy to compact IDs by hand because of references and constraints.
Does PostgreSQL itself support of ID renumbering? Or is there any plugin or maintaining utility for this job?
Maybe I can write some stored procedures? That would be very nice so I can schedule it once a year.
The question is old, but we got a new question from a desperate user on dba.SE after trying to apply what is suggested here. Find an answer with more details and explanation over there:
Compacting a sequence in PostgreSQL
The currently accepted answer will fail for most cases.
Typically, you have a PRIMARY KEY or UNIQUE constraint on an id column, which is NOT DEFERRABLE by default. (OP mentions references and constraints.) Such constraints are checked after each row, so you most likely get unique violation errors trying. Details:
Constraint defined DEFERRABLE INITIALLY IMMEDIATE is still DEFERRED?
Typically, one wants to retain the original order of rows while closing gaps. But the order in which rows are updated is arbitrary, leading to arbitrary numbers. The demonstrated example seems to retain the original sequence because physical storage still coincides with the desired order (inserted rows in desired order just a moment earlier), which is almost never the case in real world applications and completely unreliable.
The matter is more complicated than it might seem at first. One solution (among others) if you can afford to remove the PK / UNIQUE constraint (and related FK constraints) temporarily:
BEGIN;
LOCK tbl;
-- remove all FK constraints to the column
ALTER TABLE tbl DROP CONSTRAINT tbl_pkey; -- remove PK
-- for the simple case without FK references - or see below:
UPDATE tbl t -- intermediate unique violations are ignored now
SET id = t1.new_id
FROM (SELECT id, row_number() OVER (ORDER BY id) AS new_id FROM tbl) t1
WHERE t.id = t1.id;
-- Update referencing value in FK columns at the same time (if any)
SELECT setval('tbl_id_seq', max(id)) FROM tbl; -- reset sequence
ALTER TABLE tbl ADD CONSTRAINT tbl_pkey PRIMARY KEY(id); -- add PK back
-- add all FK constraints to the column back
COMMIT;
This is also much faster for big tables, because checking PK (and FK) constraint(s) for every row costs a lot more than removing the constraint(s) and adding it (them) back.
If there are FK columns in other tables referencing tbl.id, use data-modifying CTEs to update all of them.
Example for a table fk_tbl and a FK column fk_id:
WITH u1 AS (
UPDATE tbl t
SET id = t1.new_id
FROM (SELECT id, row_number() OVER (ORDER BY id) AS new_id FROM tbl) t1
WHERE t.id = t1.id
RETURNING t.id, t1.new_id -- return old and new ID
)
UPDATE fk_tbl f
SET fk_id = u1.new_id -- set to new ID
FROM u1
WHERE f.fk_id = u1.id; -- match on old ID
More in the referenced answer on dba.SE.
Assuming your ids are generated from a bignum sequence, just RESTART the sequence and update the table with idcolumn = DEFAULT.
CAVEAT: If this id column is used as a foreign key by other tables, make sure you have the on update cascade modifier turned on.
For example:
Create the table, put some data in, and remove a middle value:
db=# create sequence xseq;
CREATE SEQUENCE
db=# create table foo ( id bigint default nextval('xseq') not null, data text );
CREATE TABLE
db=# insert into foo (data) values ('hello'), ('world'), ('how'), ('are'), ('you');
INSERT 0 5
db=# delete from foo where data = 'how';
DELETE 1
db=# select * from foo;
id | data
----+-------
1 | hello
2 | world
4 | are
5 | you
(4 rows)
Reset your sequence:
db=# ALTER SEQUENCE xseq RESTART;
ALTER SEQUENCE
Update your data:
db=# update foo set id = DEFAULT;
UPDATE 4
db=# select * from foo;
id | data
----+-------
1 | hello
2 | world
3 | are
4 | you
(4 rows)
new id column and Foreign Key(s) while the old ones are still in use. With some (quick) renaming, applications do not have to be aware. (But applications should be inactive during the final renaming step)
\i tmp.sql
-- the test tables
CREATE TABLE one (
id serial NOT NULL PRIMARY KEY
, payload text
);
CREATE TABLE two (
id serial NOT NULL PRIMARY KEY
, the_fk INTEGER REFERENCES one(id)
ON UPDATE CASCADE ON DELETE CASCADE
);
-- And the supporting index for the FK ...
CREATE INDEX ON two(the_fk);
-- populate
INSERT INTO one(payload)
SELECT x::text FROM generate_series(1,1000) x;
INSERT INTO two(the_fk)
SELECT id FROM one WHERE random() < 0.3;
-- make some gaps
DELETE FROM one WHERE id % 13 > 0;
-- SELECT * FROM two;
-- Add new keycolumns to one and two
ALTER TABLE one
ADD COLUMN new_id SERIAL NOT NULL UNIQUE
;
-- UPDATE:
-- This could need DEFERRABLE
-- Note since the update is only a permutation of the
-- existing values, we dont need to reset the sequence.
UPDATE one SET new_id = self.new_id
FROM ( SELECT id, row_number() OVER(ORDER BY id) AS new_id FROM one ) self
WHERE one.id = self.id;
ALTER TABLE two
ADD COLUMN new_fk INTEGER REFERENCES one(new_id)
;
-- update the new FK
UPDATE two t
SET new_fk = o.new_id
FROM one o
WHERE t.the_fk = o.id
;
SELECT * FROM two;
-- The crucial part: the final renaming
-- (at this point it would be better not to allow other sessions
-- messing with the {one,two} tables ...
-- --------------------------------------------------------------
ALTER TABLE one DROP COLUMN id CASCADE;
ALTER TABLE one rename COLUMN new_id TO id;
ALTER TABLE one ADD PRIMARY KEY(id);
ALTER TABLE two DROP COLUMN the_fk CASCADE;
ALTER TABLE two rename COLUMN new_fk TO the_fk;
CREATE INDEX ON two(the_fk);
-- Some checks.
-- (the automatically generated names for the indexes
-- and the sequence still contain the "new" names.)
SELECT * FROM two;
\d one
\d two
UPDATE: added the permutation of new_id (after creating it as a serial)
Funny thing is: it doesn't seem to need 'DEFERRABLE'.
*This script will work for postgresql
This is a generic solution that works for all cases
This query find the desciption of the fields of all tables from any database.
WITH description_bd AS (select colum.schemaname,coalesce(table_name,relname) as table_name , column_name, ordinal_position, column_default, data_type, is_nullable, character_maximum_length, is_updatable,description from
( SELECT columns.table_schema as schemaname,columns.table_name, columns.column_name, columns.ordinal_position, columns.column_default, columns.data_type, columns.is_nullable, columns.character_maximum_length, columns.character_octet_length, columns.is_updatable, columns.udt_name
FROM information_schema.columns
) colum
full join (SELECT schemaname, relid, relname,objoid, objsubid, description
FROM pg_statio_all_tables ,pg_description where pg_statio_all_tables.relid= pg_description.objoid ) descre
on descre.relname = colum.table_name and descre.objsubid=colum.ordinal_position and descre.schemaname=colum.schemaname )
This query propose a solution to fix the sequence of all database tables (this generates a query in the req field which fixes the sequence of the different tables).
It finds the number of records of the table and then increment this number by one.
SELECT table_name, column_name, ordinal_position,column_default,
data_type, is_nullable, character_maximum_length, is_updatable,
description,'SELECT setval('''||schemaname||'.'|| replace(replace(column_default,'''::regclass)',''),'nextval(''','')||''', (select max( '||column_name ||')+1 from '|| table_name ||' ), true);' as req
FROM description_bd where column_default like '%nextva%'
Since I didn't like the answers, I wrote a function in PL/pgSQL to do the job.
It is called like this :
=> SELECT resequence('port','id','port_id_seq');
resequence
--------------
5090 -> 3919
Takes 3 parameters
name of table
name of column that is SERIAL
name of sequence that the SERIAL uses
The function returns a short report of what it has done, with the previous value of the sequence and the new value.
The function LOOPs over the table ORDERed by the named column and makes an UPDATE for each row. Then sets the new value for the sequence. That's it.
The order of the values is preserved.
No ADDing and DROPing of temporary columns or tables involved.
No DROPing and ADDing of constraints and foreign keys needed.
Of course You better have ON UPDATE CASCADE for those foreign keys.
The code :
CREATE OR REPLACE FUNCTION resequence(_tbl TEXT, _clm TEXT, _seq TEXT) RETURNS TEXT AS $FUNC$
DECLARE
_old BIGINT;_new BIGINT := 0;
BEGIN
FOR _old IN EXECUTE 'SELECT '||_clm||' FROM '||_tbl||' ORDER BY '||_clm LOOP
_new=_new+1;
EXECUTE 'UPDATE '||_tbl||' SET '||_clm||'='||_new||' WHERE '||_clm||'='||_old;
END LOOP;
RETURN (nextval(_seq::regclass)-1)||' -> '||setval(_seq::regclass,_new);
END $FUNC$ LANGUAGE plpgsql;