I'm trying to denormalize an aggregate bit of data for performance, but can't figure out how to get the aggregation working...
CREATE TABLE brands (
id SERIAL,
name TEXT,
total INTEGER,
unitcount INTEGER
)
CREATE TABLE items (
brandid INTEGER,
id SERIAL,
unitvalue INTEGER
)
UPDATE brands SET b.total = i.sumScore,
b.unitcount = i.unitcount
FROM brands b
INNER JOIN
(
SELECT brandid,
SUM(unitvalue) sumScore,
COUNT(unitvalue) unitcount
FROM items
group by brandid
) as a
ON i.brandid = b.id
This updates EVERY record in brand with the same values, despite the inner join query showing a correct table set of distinct values for each brand. How can I get that correlated?
please try
UPDATE brands b
INNER JOIN (
SELECT brandid,SUM(unitvalue) value_to_update,COUNT(unitvalue) cnt
FROM items GROUP BY brandid) abc
ON b.id=abc.brandid
SET b.total=abc.value_to_update,b.unitcount=abc.cnt
Related
I have one table with 100M plus rows which looks like this
Create table member (
id bigint,
gender text,
//..other fields
primary key (id)
);
Now the gender field has two possible value 'M' or 'F'
Whenever I am using the gender field then it's taking to much time I have indexes on other fields like id, member details, mobile number
select
count(1) filter (where mod.is_active and m.gender = 'M') as male,
count(1) filter (where mod.is_active and m.gender = 'F') as female
from member_other_details mod
inner join member m on m.id = mod.member_id
This query is taking hrs to complete
How can I optimize this?
Personnally i would execute this query
select m.gender,count(*)
from member_other_details mod inner join member m on m.id = mod.member_id
where mod.is_active
group by m.gender
I need to write a sql code that probably is very simple but I am very new to it.
I need to find all the records from one table that have matching id (but no more than one) from the other table. eg. one table contains records of the employees and the second one with employees' telephone numbers. i need to find all employees with only one telephone no
Sample data would be nice. In absence of:
SELECT
employees.employee_id
FROM
employees
LEFT JOIN
(SELECT distinct on(employee_id) employee_id FROM emp_phone) AS phone
ON
employees.employee_id = phone.employee_id
WHERE
phone.employee_id IS NOT NULL;
You need a join of the 2 tables, group by employee and the condition in the having clause:
SELECT e.employee_id, e.name
FROM employees e INNER JOIN numbers n
ON e.employee_id = n.employee_id
GROUP BY e.employee_id, e.name
HAVING COUNT(*) = 1;
If there can be more than a few numbers per employee in the table with the employees' telephone numbers (calling it tel), then it's cheaper to avoid GROUP BY and HAVING which has to process all rows. Find employees with "unique" numbers using a self-anti-join with NOT EXISTS.
While you don't need more than the employee_id and their unique phone number, you don't even have to involve the employee table at all:
SELECT *
FROM tel t
WHERE NOT EXISTS (
SELECT FROM tel
WHERE employee_id = t.employee_id
AND tel_number <> t.tel_number -- or use PK column
);
If you need additional columns from the employee table:
SELECT * -- or any columns you need
FROM (
SELECT employee_id AS id, tel_number -- or any columns you need
FROM tel t
WHERE NOT EXISTS (
SELECT FROM tel
WHERE employee_id = t.employee_id
AND tel_number <> t.tel_number -- or use PK column
)
) t
JOIN employee e USING (id);
The column alias in the subquery (employee_id AS id) is just for convenience. Then the outer join condition can be USING (id), and the ID column is only included once in the result, even with SELECT * ...
Simpler with a smart naming convention that uses employee_id for the employee ID everywhere. But it's a widespread anti-pattern to use employee.id instead.
Related:
JOIN table if condition is satisfied, else perform no join
Assuming I have a table with 3 columns, ID, Name, City and I want to use named query to return rows with unique city..can it be done?
Are you asking whether it is possible to write a query that will return the cities that appear in exactly one row, in a table that has ID/Name/City triplets where there could be multiple rows for the same city but with different names?
If so, it would depend on the database engine behind the scenes - but you could try things like:
with candidates (city, num) as (
select city, count(*) from table
group by city
)
select city from candidates where num = 1
Or
select t1.city from table t1
where not exists (
select * from table t2
where t2.city = t1.city and t2.id <> t1.id
)
where table is your table with these triplets.
I have two table like this:
create table product (
id serial primary key,
name text
);
create table selectedattribute (
id serial primary key,
product integer references product,
attribute text,
val text
);
and I'm creating a materialized view with this select query
select product.name,
jsonb_build_object(
'color', COALESCE(jsonb_agg(val) FILTER (WHERE attribute='color'), '[]'),
'diameter', COALESCE(jsonb_agg(val) FILTER (WHERE attribute='diameter'), '[]')
)
from product
left join selectedattribute on product.id = selectedattribute.product
group by product.id;
the problem with this select query is when I add a new attribute, I have to add it to select query in order to create an up-to-date materialized view.
Is there a way to write an aggregate expression that dynamically gets attributes without all these hard-coded attribute names?
You can try my code in SQL Fiddle: http://sqlfiddle.com/#!17/c4150/4
You need to nest the aggregation. First collect all values for an attribute then aggregate that into a JSON:
select id, name, jsonb_object_agg(attribute, vals)
from (
select p.id, p.name, a.attribute, jsonb_agg(a.val) vals
from product p
left join selectedattribute a on p.id = a.product
group by p.id, a.attribute
) t
group by id, name;
Updated SQLFiddle: http://sqlfiddle.com/#!17/c4150/5
There are three tables: businesses, categories, categorizations,
CREATE TABLE businesses (
id SERIAL PRIMARY KEY,
name varchar(40)
);
CREATE TABLE categories (
id SERIAL PRIMARY KEY,
name varchar(40)
);
CREATE TABLE categorizations (
business_id integer,
category_id integer
);
So business has many categories through categorizations.
If I want to select businesses without categories, I would do something
like this:
SELECT businesses.* FROM businesses
LEFT OUTER JOIN categorizations
ON categorizations.business_id = businesses.id
LEFT OUTER JOIN categories
ON categories.id = categorizations.category_id
GROUP BY businesses.id
HAVING count(categories.id) = 0;
The question is: How do I select businesses without categories AND
businesses with category named "Media" in one query?
You can use a union:
SELECT businesses.*
FROM businesses
LEFT OUTER JOIN categorizations
ON categorizations.business_id = businesses.id
GROUP BY businesses.id
HAVING count(categorizations.business_id) = 0
UNION
SELECT businesses.*
FROM businesses
INNER JOIN categorizations
ON categorizations.business_id = businesses.id
INNER JOIN categories
ON categories.id = categorizations.category_id
WHERE categories.name = 'Media';
Note that in the first instance (businesses with no categories at all) that you won't need to join as far as categories - you can detect the lack of category in the junction table. If it is possible for the same business to have the same category more than once, you'll need to introduce the second query with DISTINCT.
I would try:
SELECT b.* FROM businesses b
LEFT JOIN categorizations cz ON b.business_id = cz.business_id
LEFT JOIN categories cs ON cz.category_id = cs.category_id
WHERE COALESCE(cs.name, 'Media') = 'Media';
... in the hope that businesses with no categorizations would get NULL entries on their joins.
The double-negation trick works for this kind of selections:
SELECT * FROM businesses b
WHERE NOT EXISTS (
SELECT *
FROM categorizations bc
JOIN categories c ON bc.category_id = c.category_id
WHERE bc.business_id = b.business_id
AND c.name <> 'Media'
);