Here is my code at the moment:
CREATE TABLE sektors (
id_sektors SERIAL PRIMARY KEY,
laukuma_nosaukums varchar(100) UNIQUE,
m2 int CHECK(m2 ~ '^[^0-9]*$')
datums_no date CHECK(datums_no XXX???),
datums_lidz date CHECK(datums_lidz XXX???),
id_koka_veds int NOT NULL REFERENCES koku_veids(id_veids),
id_audzesanas_veids int NOT NULL REFERENCES audzesanas_veids(id_audzesanas_veids),
id_senu_veids int NOT NULL REFERENCES senu_veids(id_senu_veids)
);
What i want to achieve:
laukuma_nosaukums - can contain only unique entries
m2 - can contain only numbers? Dunno if this is right.
datums_no - Don't know how to write it, but i want it like this: I can enter only date that is older than current date.
datums_lidz - Don't know this either. I want it like this: I can enter only date that is NOT older than 3 months from current date.
This should do what you need for your date fields. Importantly, use current_date, and not now(). The former is a special system variable. The latter will evaluate when you create the table, leading to errors as soon as the date changes.
create table sektors (
...
datums_no date
CHECK (old_date < current_date),
datums_lidz date
CHECK (not_old_date <= (current_date + '3 months'::interval)),
...
);
Related
I have 2 tables in my postgresql timescaledb database (version 12.06) that I try to query through inner join.
Tables' structure:
CREATE TABLE currency(
id serial PRIMARY KEY,
symbol TEXT NOT NULL,
name TEXT NOT NULL,
quote_asset TEXT
);
CREATE TABLE currency_price (
currency_id integer NOT NULL,
dt timestamp WITHOUT time ZONE NOT NULL,
open NUMERIC NOT NULL,
high NUMERIC NOT NULL,
low NUMERIC NOT NULL,
close NUMERIC,
volume NUMERIC NOT NULL,
PRIMARY KEY (
currency_id,
dt
),
CONSTRAINT fk_currency FOREIGN KEY (currency_id) REFERENCES currency(id)
);
The query I'm trying to make is:
SELECT currency_id AS id, symbol, MAX(close) AS close, DATE(dt) AS date
FROM currency_price
JOIN currency ON
currency.id = currency_price.currency_id
GROUP BY currency_id, symbol, date
LIMIT 100;
Basically, it returns all the rows that exist in currency_price table. I know that postgres doesn't allow select columns without an aggregate function or including them in "group by" clause. So, if I don't include dt column in my select query, i receive expected results, but if I include it, the output shows rows of every single day of each currency while I only want to have the max value of every currency and filter them out based on various dates afterwards.
I'm very inexperienced with SQL in general.
Any suggestions to solve this would be very appreciated.
There are several ways to do it, easiest one comes to mind is using window functions.
select *
from (
SELECT currency_id,symbol,close,dt
,row_number() over(partition by currency_id,symbol
order by close desc,dt desc) as rr
FROM currency_price
JOIN currency ON currency.id = currency_price.currency_id
where dt::date = '2021-06-07'
)q1
where rr=1
General window functions:
https://www.postgresql.org/docs/9.5/functions-window.html
works also with standard aggregate functions like SUM,AVG,MAX,MIN and others.
Some examples: https://www.postgresqltutorial.com/postgresql-window-function/
In my table I have the following scheme:
id - integer | date - text | name - text | count - integer
I want just to count some actions.
I want put 1 when date = '30-04-2019' not exist yet.
I want put +1 when is row already exist.
My idea is:
UPDATE "call" SET count = (1 + (SELECT count
FROM "call"
WHERE date = '30-04-2019'))
WHERE date = '30-04-2019'
But it is not working when row doesn't exist.
It is possible without some extra triggers, etc...
You can use a writeable CTE to achieve this. Additionally the UPDATE statement can be simplified to a simple set count = count + 1 there is no need for a sub-select.
with updated as (
update "call"
set count = count + 1
where date = '30-04-2019'
returning id
)
insert into "call" (date, count)
select '30-04-2019', 1
where not exists (select *
form updated);
If the update did not find a row, the where not exists condition will be true and the insert will be executed.
Note that the above is not safe for concurrent execution from multiple transactions. If you want to make this safe, create a unique index on the date column. Then use an INSERT ... ON CONFLICT instead:
insert into "call" (date, count)
values ('30-04-2019', 1)
on conflict (date)
do update
set count = "call".count + 1;
Again: the above requires a unique index (or constraint) on the date column.
Unrelated to the immediate problem, but: storing dates in a text column is a really, really bad idea. You should change your table definition and change the data type for the "date" column to date.
I have a date column which I want to be unique once populated, but want the date field to be ignored if it is not populated.
In MySQL the way this is accomplished is to set the date column to "not null" and give it a default value of '0000-00-00' - this allows all other fields in the unique index to be "checked" even if the date column is not populated yet.
This does not work in PosgreSQL because '0000-00-00' is not a valid date, so you cannot store it in a date field (this makes sense to me).
At first glance, leaving the field nullable seemed like an option, but this creates a problem:
=> create table uniq_test(NUMBER bigint not null, date DATE, UNIQUE(number, date));
CREATE TABLE
=> insert into uniq_test(number) values(1);
INSERT 0 1
=> insert into uniq_test(number) values(1);
INSERT 0 1
=> insert into uniq_test(number) values(1);
INSERT 0 1
=> insert into uniq_test(number) values(1);
INSERT 0 1
=> select * from uniq_test;
number | date
--------+------
1 |
1 |
1 |
1 |
(4 rows)
NULL apparently "isn't equal to itself" and so it does not count towards constraints.
If I add an additional unique constraint only on the number field, it checks only number and not date and so I cannot have two numbers with different dates.
I could select a default date that is a 'valid date' (but outside working scope) to get around this, and could (in fact) get away with that for the current project, but there are actually cases I might be encountering in the next few years where it will not in fact be evident that the date is a non-real date just because it is "a long time ago" or "in the future."
The advantage the '0000-00-00' mechanic had for me was precisely that this date isn't real and therefore indicated a non-populated entry (where 'non-populated' was a valid uniqueness attribute). When I look around for solutions to this on the internet, most of what I find is "just use NULL" and "storing zeros is stupid."
TL;DR
Is there a PostgreSQL best practice for needing to include "not populated" as a possible value in a unique constraint including a date field?
Not clear what you want. This is my guess:
create table uniq_test (number bigint not null, date date);
create unique index i1 on uniq_test (number, date)
where date is not null;
create unique index i2 on uniq_test (number)
where date is null;
There will be an unique constraint for not null dates and another one for null dates effectively turning the (number, date) tuples into distinct values.
Check partial index
It's not a best practice, but you can do it such way:
t=# create table so35(i int, d date);
CREATE TABLE
t=# create unique index i35 on so35(i, coalesce(d,'-infinity'));
CREATE INDEX
t=# insert into so35 (i) select 1;
INSERT 0 1
t=# insert into so35 (i) select 2;
INSERT 0 1
t=# insert into so35 (i) select 2;
ERROR: duplicate key value violates unique constraint "i35"
DETAIL: Key (i, (COALESCE(d, '-infinity'::date)))=(2, -infinity) already exists.
STATEMENT: insert into so35 (i) select 2;
I'm trying to retrieve data from my database using the find() method.
But when I use find('all') it returns the column value and column name together, like this: { "date_1": "2015-25-12"}, of course, I want only the values from the column.
If I use find('list'), it comes back empty.
This is how I'm trying to retrieve my data:
$date1 = $this->Stocks->find('all', ['fields' => ['Stocks.date_1'], 'conditions' => ['Stocks.families_id' => $id]]);
This is my table:
CREATE TABLE stocks
(
families_id integer,
date_1 date NOT NULL,
date_2 date,
created timestamp without time zone,
modified timestamp without time zone,
id serial NOT NULL,
CONSTRAINT stocks_pkey PRIMARY KEY (id)
)
Everything else is working fine, but this one part.
I'm using PostgreSQL.
Although you problem was related to displayField.
To select a single column or a set of columns you can do like this
$date1 = $this->Stocks->find()
->select(['date_1'])
->where(['families_id' => $id]);
I'm using postgresql 9.0 beta 4.
After inserting a lot of data into a partitioned table, i found a weird thing. When I query the table, i can see an empty row with null-like values in 'not-null' fields.
That weird query result is like below.
689th row is empty. The first 3 fields, (stid, d, ticker), are composing primary key. So they should not be null. The query i used is this.
select * from st_daily2 where stid=267408 order by d
I can even do the group by on this data.
select stid, date_trunc('month', d) ym, count(*) from st_daily2
where stid=267408 group by stid, date_trunc('month', d)
The 'group by' results still has the empty row.
The 1st row is empty.
But if i query where 'stid' or 'd' is null, then it returns nothing.
Is this a bug of postgresql 9b4? Or some data corruption?
EDIT :
I added my table definition.
CREATE TABLE st_daily
(
stid integer NOT NULL,
d date NOT NULL,
ticker character varying(15) NOT NULL,
mp integer NOT NULL,
settlep double precision NOT NULL,
prft integer NOT NULL,
atr20 double precision NOT NULL,
upd timestamp with time zone,
ntrds double precision
)
WITH (
OIDS=FALSE
);
CREATE TABLE st_daily2
(
CONSTRAINT st_daily2_pk PRIMARY KEY (stid, d, ticker),
CONSTRAINT st_daily2_strgs_fk FOREIGN KEY (stid)
REFERENCES strgs (stid) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE CASCADE,
CONSTRAINT st_daily2_ck CHECK (stid >= 200000 AND stid < 300000)
)
INHERITS (st_daily)
WITH (
OIDS=FALSE
);
The data in this table is simulation results. Multithreaded multiple simulation engines written in c# insert data into the database using Npgsql.
psql also shows the empty row.
You'd better leave a posting at http://www.postgresql.org/support/submitbug
Some questions:
Could you show use the table
definitions and constraints for the
partions?
How did you load your data?
You get the same result when using
another tool, like psql?
The answer to your problem may very well lie in your first sentence:
I'm using postgresql 9.0 beta 4.
Why would you do that? Upgrade to a stable release. Preferably the latest point-release of the current version.
This is 9.1.4 as of today.
I got to the same point: "what in the heck is that blank value?"
No, it's not a NULL, it's a -infinity.
To filter for such a row use:
WHERE
case when mytestcolumn = '-infinity'::timestamp or
mytestcolumn = 'infinity'::timestamp
then NULL else mytestcolumn end IS NULL
instead of:
WHERE mytestcolumn IS NULL