How to alter existing column auto increment in existing DB2-Table?
If you created a table with a normal column, like an id column here:
CREATE TABLE demo_tab
(id int NOT NULL PRIMARY KEY,
col_txt VARCHAR(20)
);
but later you decided to have it like this one with the GENERATED ALWAYS AS IDENTITY clause:
CREATE TABLE demo_tab
(id int NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1) PRIMARY KEY,
col_txt VARCHAR(20)
);
use this statement:
ALTER TABLE demo_tab ALTER COLUMN id
SET GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1);
and do not forget about reorganising the table:
CALL SYSPROC.ADMIN_CMD('REORG TABLE demo_tab');
if you want modify your identityvalue try this
ALTER TABLE yourtable ALTER COLUMN youridentitycomunname RESTART WITH yourcountervalue
Related
I am firstly creating a table like this:
CREATE TABLE public.case_change (
id integer NOT NULL GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
to_quantity integer NOT NULL,
to_cancelled_quantity integer NOT NULL DEFAULT 0,
to_completed_quantity integer NOT NULL DEFAULT 0,
to_outstanding_quantity integer GENERATED ALWAYS AS (to_quantity - to_cancelled_quantity - to_completed_quantity) STORED NOT NULL
);
And then I am applying this:
alter table public.case_change alter column to_outstanding_quantity DROP EXPRESSION;
alter table public.case_change alter column to_outstanding_quantity set DEFAULT 0;
which will set to_outstanding_quantity to be the same as to_completed_quantity.
Now I would like to set it back to exactly how it was before (generated ), how do I do that?
I've tried this but I'm getting syntax error :
alter table public.case_change ALTER column to_outstanding_quantity SET GENERATED ALWAYS(to_quantity - to_cancelled_quantity - to_completed_quantity) STORED NOT NULL;
You are going to have to:
alter table public.case_change drop column to_outstanding_quantity;
alter table public.case_change ADD column to_outstanding_quantity
GENERATED ALWAYS AS (to_quantity - to_cancelled_quantity - to_completed_quantity )
STORED;
I'm currently trying the inheritance system with PostgreSQL but I have a problem with the auto-increment index in my child tables.
I have three tables: "Currency", "Crypto" and "Stable"
CREATE TABLE IF NOT EXISTS public.currency
(
id INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
name VARCHAR(30) UNIQUE NOT NULL,
symbol VARCHAR(10) UNIQUE NOT NULL,
);
CREATE TABLE IF NOT EXISTS public.stable (id INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY) INHERITS (public.currency);
CREATE TABLE IF NOT EXISTS public.crypto (id INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY) INHERITS (public.currency);
I insered my data like this:
INSERT INTO public.stable (name, symbol) VALUES ('Euro', '€'), ('Dollar', '$'), ('Tether', 'USDT');
INSERT INTO public.crypto (name, symbol) VALUES ('Bitcoin', 'BTC'), ('Ethereum', 'ETH'), ('Litcoin', 'LTC');
But this is my problem: I would like to have a unique identifier that increments itself through my parent table "Currency".
When I select, I have (take a look in my id: 1,2,3,1,2,3):
But, Is it possible to have something like this instead (1,2,3,4,5,6):
Is it a problem in my primary key?
Thank you
We can try to use create sequence to set row numbers for sharing between multiple tables.
define a new sequence generator
create sequence n_id;
Then we can use this sequence as below, sharing this sequence for those three tables.
create sequence n_id;
CREATE TABLE IF NOT EXISTS currency
(
id INT default nextval('n_id') PRIMARY KEY,
name VARCHAR(30) UNIQUE NOT NULL,
symbol VARCHAR(10) UNIQUE NOT NULL
);
CREATE TABLE IF NOT EXISTS stable (id INT default nextval('n_id') PRIMARY KEY) INHERITS (currency);
CREATE TABLE IF NOT EXISTS crypto (id INT default nextval('n_id') PRIMARY KEY) INHERITS (currency);
sqlfiddle
#Error description:
It's possible to create a table that has a foreign key into a hypertable provided the foreign key is defined when the table is created
#To Reproduce, there are next tables:
CREATE TABLE ids (
measurement_id int DEFAULT 0,
description text DEFAULT 0,
m_id bigserial NOT NULL,
service_id int DEFAULT NULL,
time bigint NOT NULL DEFAULT cast((EXTRACT(EPOCH FROM now() AT TIME ZONE 'UTC') * 1000) as bigint),
user_id int DEFAULT NULL,
end_time DOUBLE PRECISION DEFAULT 0,
start_time int NOT NULL DEFAULT 0
);
CREATE INDEX ON ids (time DESC, user_id);
CREATE INDEX ON ids (time DESC, service_id);
SELECT create_hypertable('ids', 'start_time', chunk_time_interval => 604800016);
---------
CREATE TABLE IF NOT EXISTS metrics (
id bigserial NOT NULL,
duration real DEFAULT NULL,
metric integer DEFAULT 0,
m_id bigint NOT NULL,
time bigint NOT NULL DEFAULT 0
);
ALTER TABLE metrics ADD PRIMARY KEY (time, m_id);
CREATE INDEX ON metrics (time DESC);
CREATE INDEX ON metrics (time DESC, measurement );
CREATE INDEX ON metrics (time DESC, m_id );
grant all privileges on ids, metrics to your_db_user;
SELECT create_hypertable('metrics', 'time' , chunk_time_interval => 604800016);
SELECT table_catalog, table_schema, table_name, privilege_type FROM information_schema.table_privileges WHERE grantee = 'your_db_user';
---------
DROP TABLE IF EXISTS resource;
CREATE TABLE resource(
id int NOT NULL,
cpu text DEFAULT 0,
storing text DEFAULT 0,
memory text DEFAULT 0
);
ALTER TABLE resource ADD PRIMARY KEY (id);
CREATE SEQUENCE resource_id_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 2147483647
START 1
CACHE 1;
ALTER TABLE resource_id_seq
OWNER TO your_db_user;
ALTER TABLE resource ALTER COLUMN id SET DEFAULT nextval('resource_id_seq'::regclass);
---------
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
DROP TABLE IF EXISTS ns;
CREATE TABLE ns(
id bigint NOT NULL,
uuid uuid NOT NULL DEFAULT uuid_generate_v4 (),
availability double precision,
faultTolerance boolean,
activated boolean,
UNIQUE (id, uuid),
PRIMARY KEY(id),
CONSTRAINT fk_resource
FOREIGN KEY(id)
REFERENCES resource(id)
ON DELETE CASCADE
);
CREATE SEQUENCE ns_id_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 9223372036854775807
START 1
CACHE 1;
ALTER TABLE ns_id_seq
OWNER TO your_db_user;
ALTER TABLE ns ALTER COLUMN id SET DEFAULT nextval('ns_id_seq'::regclass);
---------
DROP TABLE IF EXISTS authentication;
CREATE TABLE authentication(
id integer NOT NULL,
username character varying(255) NOT NULL,
password character varying(255) NOT NULL,
host character varying(255) NOT NULL,
port character varying(10) NOT NULL,
PRIMARY KEY(id)
);
CREATE SEQUENCE auth_id_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 2147483647
START 1
CACHE 1;
ALTER TABLE auth_id_seq
OWNER TO your_db_user;
ALTER TABLE authentication ALTER COLUMN id SET DEFAULT nextval('auth_id_seq'::regclass);
---------
DROP TABLE IF EXISTS job;
CREATE TABLE job(
id int NOT NULL,
interval integer NOT NULL,
auth_id integer REFERENCES authentication (id),
ns_id integer REFERENCES ns (id),
UNIQUE (auth_id, ns_id),
PRIMARY KEY(id)
);
ALTER TABLE job
ADD CONSTRAINT fk_auth_id
FOREIGN KEY (id) REFERENCES authentication (id)
ON DELETE CASCADE
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE job
ADD CONSTRAINT fk_ns_id
FOREIGN KEY (id) REFERENCES ns (id)
ON DELETE CASCADE
DEFERRABLE INITIALLY DEFERRED;
CREATE SEQUENCE job_id_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 2147483647
START 1
CACHE 1;
ALTER TABLE job_id_seq
OWNER TO your_db_user;
ALTER TABLE job ALTER COLUMN id SET DEFAULT nextval('job_id_seq'::regclass);
---------
DROP TABLE IF EXISTS job_metric;
CREATE TABLE job_metric (
id int NOT NULL,
j_id int NOT NULL REFERENCES job (id),
mj_id bigint NOT NULL,
jm_time bigint NOT NULL
);
CREATE INDEX ON job_metric (jm_time DESC);
CREATE INDEX ON job_metric (jm_time DESC, id);
CREATE INDEX ON job_metric (jm_time DESC, mj_id);
ALTER TABLE job_metric ADD PRIMARY KEY (jm_time, id);
grant all privileges on job_metric to your_db_user;
SELECT create_hypertable('job_metric', 'jm_time' , chunk_time_interval => 604800016);
CREATE SEQUENCE mjob_metric_id_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 2147483647
START 1
CACHE 1;
ALTER TABLE mjob_metric_id_seq
OWNER TO your_db_user;
ALTER TABLE job_metric ALTER COLUMN id SET DEFAULT nextval('mjob_metric_id_seq'::regclass);
---------
After creating the tables, I have used the solution proposed by #Laurenz in a database with PostgreSQL 12.6 using the extension of timescaledb 1.7.5 as follows:
#To fill the table with the appropriate values:
UPDATE job_metric AS jm_point
SET jm_time = qm.time
FROM metrics AS qm
WHERE qm.m_id = jm_point.mj_id;
#Then set it NOT NULL:
ALTER TABLE job_metric ALTER jm_time SET NOT NULL;
#To define your foreign key:
ALTER TABLE job_metric
ADD FOREIGN KEY (mj_id, jm_time)
REFERENCES metrics (time, m_id) MATCH FULL;
#Response of the last reference table to enable foreign key: Query returned successfully in 40 msec.
Expected behavior:
The idea is to use the table job_metric in an even many-to-many relationship to access the information of job and metrics tables.
Actual behavior and error:
Tables are created and FKs were created but cannot be used when data is inserted at job_metric as is detailed in the following:
INSERT INTO job_metric (j_id, mj_id, jm_time)
VALUES(13, 185063, 1621957192266);
ERROR: foreign keys to hypertables are not supported CONTEXT: SQL
statement " ALTER TABLE _timescaledb_internal._hyper_5_5_chunk ADD
CONSTRAINT "5_13_job_metric_j_id_mj_id_jm_time_fkey" FOREIGN KEY
(j_id, mj_id, jm_time) REFERENCES qmetrics("time", m_id) MATCH FULL "
PL/pgSQL function
_timescaledb_internal.chunk_constraint_add_table_constraint(_timescaledb_catalog.chunk_constraint)
line 42 at EXECUTE SQL state: 0A000
***According to https://docs.timescale.com/timescaledb/latest/overview/limitations/##distributed-hypertable-limitations, it looks like the above error is part of the hypertable limitations:
Foreign key constraints referencing a hypertable are not supported.
#Request:
Given the above information and errors, does anyone know any solution at the DB level to establish the relationships (many-to-many or one-to-many) using timescaledb extension and mainly hypertables?
Actually, I have obtained similar of above error when I had attempted to create many-to-many relation among the tables metrics and job_metric using the Django Rest Framework:
class Job_Metrics(models.Model):
job = models.OneToOneField(Job, on_delete=models.CASCADE)
metrics = models.ManyToManyField(Metrics)
time = models.IntegerField(default=0)
Running the application metrics pointing out directly metrics_db:
$ python3 manage.py migrate metrics --database=metrics_db
Operations to perform: Apply all migrations: metrics Running migrations: Applying
metrics.0002_job...Traceback (most recent call last): File
"/var/myproject/myprojectenv/lib/python3.8/site-packages/django/db/backends/utils.py",
line 84, in _execute return self.cursor.execute(sql, params)
psycopg2.errors.FeatureNotSupported: foreign keys to hypertables are
not supported
If someone knows a solution or has an idea to deal with the above error at the REST API level, please could you share your idea with the aim to access data associated tables (metrics and jobs) and modify them together when is required to delete e.g., a job_metric. So far, using hypertables amendments of timescaledb extension seems to be not a viable solution.
Is there a way to change existing primary key type from int to serial without dropping the table? I already have a lot of data in the table and I don't want to delete it.
Converting an int to a serial more or less only means adding a sequence default to the value, so to make it a serial;
Pick a starting value for the serial, greater than any existing value in the table
SELECT MAX(id)+1 FROM mytable
Create a sequence for the serial (tablename_columnname_seq is a good name)
CREATE SEQUENCE test_id_seq MINVALUE 3 (assuming you want to start at 3)
Alter the default of the column to use the sequence
ALTER TABLE test ALTER id SET DEFAULT nextval('test_id_seq')
Alter the sequence to be owned by the table/column;
ALTER SEQUENCE test_id_seq OWNED BY test.id
A very simple SQLfiddle demo.
And as always, make a habit of running a full backup before running altering SQL queries from random people on the Internet ;-)
-- temp schema for testing
-- ----------------------------
DROP SCHEMA tmp CASCADE;
CREATE SCHEMA tmp ;
SET search_path=tmp;
CREATE TABLE bagger
( id INTEGER NOT NULL PRIMARY KEY
, tralala varchar
);
INSERT INTO bagger(id,tralala)
SELECT gs, 'zzz_' || gs::text
FROM generate_series(1,100) gs
;
DELETE FROM bagger WHERE random() <0.9;
-- SELECT * FROM bagger;
-- CREATE A sequence and tie it to bagger.id
-- -------------------------------------------
CREATE SEQUENCE bagger_id_seq;
ALTER TABLE bagger
ALTER COLUMN id SET NOT NULL
, ALTER COLUMN id SET DEFAULT nextval('player_id_seq')
;
ALTER SEQUENCE bagger_id_seq
OWNED BY bagger.id
;
SELECT setval('bagger_id_seq', MAX(ba.id))
FROM bagger ba
;
-- Check the result
-- ------------------
SELECT * FROM bagger;
\d bagger
\d bagger_id_seq
I'm trying to generate a random key including current inserting column value in oracle is it possible to create?
CREATE TABLE MY_TABLE
(
KEY VARCHAR2(12) not null,
SITEID varchar2(25) not null,
SITENAME varchar2(50),
CONSTRAINT MY_pk PRIMARY KEY (KEY)
);
INSERT INTO MY_TABLE (KEY, SITEID, SITENAME)
VALUES(('ABCD001'||SITEID), 'HYD001', 'HYDERABADSITE');
It would be better to use a BEFORE TRIGGER to do this. like,
CREATE OR REPLACE
TRIGGER my_table_trigger
BEFORE INSERT ON my_table
FOR EACH ROW
BEGIN
:NEW.KEY := 'ABCD001'||:NEW.siteid;
END;