In MySQL, I have two tables with a 1:n relationship.
Table items has products, whose state is kept in another table, like so :
items:
id |ref_num|name |...
1 |0001 |product1|...
2 |0002 |product2|...
items_states :
id|product_id|state_id|date
1 |1 |5 |2010-05-05 10:25:20
2 |1 |9 |2010-05-08 12:38:00
3 |1 |6 |2010-05-10 20:45:12
...
The states table is not relevant and only relates the state_id to the state name and so on.
How can I get products where the latest state is the one I specify, one item per row?
Thank you
You may want to try the following:
SELECT i.ref_num, i.name, s.latest_date
FROM items i
JOIN (
SELECT product_id, MAX(date) as latest_date
FROM items_states
GROUP BY product_id
) s ON (s.product_id = i.id);
If you want to return just one item, simply add a WHERE i.id = ? to the query.
Test case:
CREATE TABLE items (id int, ref_num varchar(10), name varchar(10));
CREATE TABLE items_states (id int, product_id int, state_id int, date datetime);
INSERT INTO items VALUES (1, '0001', 'product1');
INSERT INTO items VALUES (2, '0002', 'product2');
INSERT INTO items_states VALUES (1, 1, 5, '2010-05-05 10:25:20');
INSERT INTO items_states VALUES (2, 1, 9, '2010-05-08 12:38:00');
INSERT INTO items_states VALUES (3, 1, 6, '2010-05-10 20:45:12');
Result:
+---------+----------+---------------------+
| ref_num | name | latest_date |
+---------+----------+---------------------+
| 0001 | product1 | 2010-05-10 20:45:12 |
+---------+----------+---------------------+
1 row in set (0.02 sec)
Either LEFT JOIN the items_states table to itself, requiring a second.date > first.date, and put a WHERE second.id IS NULL clause in it:
SELECT a.*
FROM item_states a
LEFT JOIN item_states b
ON a.product_id = b.product_id
AND b.product_id > a.product_id
WHERE b.id IS NULL AND a.state_id = <desired state>
Or make a row based query: see Mark Byers' example.
Related
I have a JSON_ARRAY of ids in the form of [1,3,...]. Each value represents an id to a value in another table.
Table: pets
id | value
1 | cat
2 | dog
3 | hamster
Table: pet_owner
id | pets_array
1 | [1, 3]
2 | [2]
3 | []
What I want to get when I query pet_owners is the following result:
Table: pet_owner
id | pets_array
1 | ["cat", "hamster"]
2 | ["dog"]
3 | []
How do I run a sub-select on each array element to get its value?
As JSON goes, it is always a pain to handle
When you need also all that have no pets, you must left Join the owner table
CREATE TABLE pet_owner (
`id` INTEGER,
`pets_array` JSON
);
INSERT INTO pet_owner
(`id`, `pets_array`)
VALUES
('1', '[1, 3]'),
('2', '[2]'),
('3', '[]');
CREATE TABLE pets (
`id` INTEGER,
`value` VARCHAR(7)
);
INSERT INTO pets
(`id`, `value`)
VALUES
('1', 'cat'),
('2', 'dog'),
('3', 'hamster');
SELECT
t1.id,
JSON_ARRAYAGG(
p.`value`
) AS pets_array
FROM(
SELECT *
FROM pet_owner ,
JSON_TABLE(
pet_owner.pets_array , "$[*]"
COLUMNS(IDs int PATH "$" NULL ON ERROR DEFAULT '0' ON EMPTY )
) AS J_LINK ) t1
LEFT JOIN pets p ON p.id =t1.IDs
GROUP BY
t1.id
;
id | pets_array
-: | :-----------------
1 | ["cat", "hamster"]
2 | ["dog"]
db<>fiddle here
A normalized Table would spare you to convert the data into usable columns.
You can join on json_contains(), then re-aggregate:
select po.id, json_arrayagg(p.value) as owners
from pet_owner po
left join pets p on json_contains(po.pets_array, cast(p.id as char))
group by po.id
Note that, unlike most (if not all!) other databases, MySQL does not guarantee the ordering of elements in an array generated by json_arrayagg(): that's just a fact we have to live with as of the current version.
Table 1
|id|name|address|car_id |
|1 |Alex|US |NULL |
|2 |Jaso|Canada |1 |
Table 2
|car_id|color|
|1 |red |
|2 |blue |
I am trying to update Alex's car_id with the car_id of the blue car in the second table. Is it possible to do it in one query?
I tried writing the query below, but couldn't make it work. Any ideas?
UPDATE table1
SET table1.car_id = table2.car_id
FROM table1
JOIN table2
ON table2.color = "blue"
WHERE table1.name = "Alex"
Desired result:
|id|name|address|car_id |
|1 |Alex|US |2 |
|2 |Jaso|Canada |1 |
I suspect it does not work in one query. [Edit: Wrong, see other answer]
You have 2 different requirements for 2 different tables which do not have a common column.
You need to find the blue car_id independently from Alexes row as they are not linked in any way by now.
I would do it as follows:
UPDATE
table1
SET
table.car_id = (
SELECT
car_id
FROM
table2
WHERE
color LIKE 'blue'
)
WHERE
name LIKE 'Alex'
update firstTable join secondTable on secondTable.color = 'blue' set firstTable.car_id = secondTable.car_id where firstTable.car_id is null;
I have a solution for a similar problem with more people and more cars.
Maybe it helps DBfiddle example
The base datatabke are as follows
CREATE TABLE Table1
(`id` int, `name` varchar(4), `address` varchar(7), `car_id` varchar(4))
;
INSERT INTO Table1
(`id`, `name`, `address`, `car_id`)
VALUES
(1, 'Alex', 'US', NULL),
(2, 'Jaso', 'Canad a', '1'),
(3, 'Paso', 'Canad a', NULL),
(4, 'Paso', 'danad a', NULL)
;
CREATE TABLE Table2
(`car_id` int, `color` varchar(7))
;
INSERT INTO Table2
(`car_id`, `color`)
VALUES
(1, 'red'),
(2, 'blue'),
(3, 'green') ,
(4, 'purple')
;
The sql statement for mysql till 5.7
Update Table1 t1a inner Join
(Select tab1.id, tab2.car_id From
( Select
`id`,
#curRank := #curRank + 1 AS rank
FROM Table1, (SELECT #curRank := 0) r
WHERE car_id IS NULL ) tab1
inner join
( Select
car_id,
#curRank2 := #curRank2 + 1 AS rank
From Table2 , (SELECT #curRank2 := 0) r Where car_id NOT IN
(
Select Car_id From
(Select GROUP_CONCAT(t1.car_id) car_id FROM Table1 as t1) t1e
WHERE car_id IS NOT NULL GROUP BY car_id
)
) tab2
ON tab1.rank = tab2.rank) t2a
on t1a.id = t2a.id
SET t1a.car_id = t2a.car_ID
;
The Problem that we face here is that we need actually the car_ids from table taht are already taken. And then select only rest of the car_id, that are not selected yet.
After that we have to make the statement so that ver person gets one color ann that every colour is selected only once. that takes a little code because we have no relationship betwenn tabel1 car_ids thta are NULL and table2.
So result is
id name address car_id
1 Alex US 2
2 Jaso Canad a 1
3 Paso Canad a 3
4 Paso danad a 4
With mysql 8 you use window function instead of the vehicle rank.
I want to Join to table. the condition is I want to only join those rows which have only one row to match. eg.
books:
id | name | price
1 | book1 | 19
2 | book2 | 19
3 | book3 | 30
price_offer:
id | offer | price
1 | offer1 | 19
2 | offer2 | 30
so now if I do select query on these table:
SELECT * FROM price_offer
JOIN books ON price_offer.price = books.price
I only want to join book with id 3 as it have only one match with price_offer table.
You could use a self join for books table to pick a book with only single match
select po.*, b1.*
from price_offer po
join books b1 on po.price = b1.price
join (
select price,max(id) id
from books
group by price
having count(*) = 1
) b2 on b1.id = b2.id
Demo
Try following query:
Sample data:
create table books(id int, name varchar(10), price int);
insert into books values
(1, 'book1', 19),
(2, 'book2', 19),
(3, 'book3', 30);
create table price_offer(id int, offer varchar(10), price int);
insert into price_offer values
(1, 'offer1', 19),
(2, 'offer2', 30);
Query:
select max(b.id)
from price_offer p
left join books b on b.price = p.price
where p.id is not null
group by b.price
having count(*) = 1;
If you want to avoid nesting queries where you have to use self-joins, you can use window-functions of MySQL 8.0.11, which are exactly for cases like this
Here's the SQLFiddle with schema and data.
I'm trying to sum 2 columns, one at parent level and the other at child level.
The current query I'm using gives me the right sum amount on child level, but doubles up the amount on parent level, due to another 1-many relationship involved on the child level.
Ugh... that's a terrible explanation - here's the English version:
Joe the salesman is involved in 2 sales.
For the 1st sale, he get's 2 sets of commissions, based on 2 different commission types. I'm trying to show Joe's total sale value, alongside the total value of his applicable splits. The split value total is fine, but sale value get's doubled up because I'm obviously, grouping/joining incorrectly (see the last example below).
This is fine:
select sp.person_name, pr.description,
sum(spl.split) as SplitValue
from sale s, product pr, sales_person sp, sales_split spl
where s.product_id = pr.id
and s.id = spl.sale_id
and sp.id = spl.sales_person_id
group by sp.id;
person_name | description | SplitValue
----------- ----------- | ----------
Joe | Widget 1 | 50
Sam | Widget 1 | 10
This is also yields the correct split and sale values, but now 3 rows are displayed for Joe (i.e 2nd row is a duplicate of the 1st one) - I only want to display Joe's "Widget 1" sale once, so not correct:
select sp.person_name, pr.description,
sum(s.sale_value) as SaleValue, sum(spl.split) as SplitValue
from sale s, product pr, sales_person sp, sales_split spl, sales_split_agreement ssa
where s.id = spl.sale_id
and s.product_id = pr.id
and sp.id = spl.sales_person_id
and sp.id = ssa.sales_person_id
and spl.sales_person_id = ssa.sales_person_id
and ssa.id = spl.sales_split_agreement_id
group by sp.id, spl.id;
person_name | description | SplitValue | SaleValue
----------- ----------- ---------- ---------
Joe | Widget 1 | 10 | 20
Joe | Widget 1 | 10 | 20
Joe | Widget 2 | 30 | 30
Sam | Widget 1 | 10 | 20
Now the duplicated row is gone, but Joe's SaleValue is incorrect - it should be 50, not 70:
select sp.person_name, pr.description,
sum(spl.split) as SplitValue, sum(s.sale_value) as SaleValue
from sale s, product pr, sales_person sp, sales_split spl, sales_split_agreement ssa
where s.id = spl.sale_id
and s.product_id = pr.id
and sp.id = spl.sales_person_id
and sp.id = ssa.sales_person_id
and spl.sales_person_id = ssa.sales_person_id
and ssa.id = spl.sales_split_agreement_id
group by sp.id;
person_name | description | SplitValue | SaleValue
----------- ----------- --------- ----------
Joe | Widget 1 | 50 | 70
Sam | Widget 1 | 10 | 20
I.e. I'm after the query that will yield this result (i.e. Joe's correct SaleValue of 50):
person_name | description | SplitValue | SaleValue
----------- ----------- --------- ----------
Joe | Widget 1 | 50 | 50
Sam | Widget 1 | 10 | 20
Any help will be greatly appreciated!
UPDATE 1:
For clarity - here's the schema and test data from the fiddle:
CREATE TABLE product
(`id` int, `description` varchar(12))
;
INSERT INTO product
(`id`, `description`)
VALUES
(1, 'Widget 1'),
(2, 'Widget 2')
;
CREATE TABLE sales_person
(`id` int, `person_name` varchar(7))
;
INSERT INTO sales_person
(`id`, `person_name`)
VALUES
(1, 'Joe'),
(2, 'Sam')
;
CREATE TABLE sale
(`id` int, `product_id` int, `sale_value` int)
;
INSERT INTO sale
(`id`, `product_id`, `sale_value`)
VALUES
(1, 1, 20.00),
(2, 2, 30.00)
;
CREATE TABLE split_type
(`id` int, `description` varchar(6))
;
INSERT INTO split_type
(`id`, `description`)
VALUES
(1, 'Type 1'),
(2, 'Type 2')
;
CREATE TABLE sales_split_agreement
(`id` int, `sales_person_id` int, `split_type_id` int, `percentage` int)
;
INSERT INTO sales_split_agreement
(`id`, `sales_person_id`, `split_type_id`, `percentage`)
VALUES
(1, 1, 1, 50),
(2, 1, 2, 50),
(3, 2, 1, 50),
(4, 1, 1, 100)
;
CREATE TABLE sales_split
(`id` int, `sale_id` int, `sales_split_agreement_id` int, `sales_person_id` int, `split` int )
;
INSERT INTO sales_split
(`id`, `sale_id`, `sales_split_agreement_id`, `sales_person_id`, `split`)
VALUES
(1, 1, 1, 1, 10),
(2, 1, 2, 1, 10),
(3, 1, 3, 2, 10),
(4, 2, 4, 1, 30)
;
I think you were on to the right track, but I decided to restart and approach from the beginning. Getting the SplitValue for each person does not require all those tables. In fact, all you need are sales_split and sales_person, like this:
SELECT sp.person_name, SUM(ss.split) AS SplitValue
FROM sales_person sp
JOIN sales_split ss ON sp.id = ss.sales_person_id
GROUP BY sp.id;
Similarly, you can get the total sale value for each person with a join between sale, sales_split, and sales_person:
SELECT sp.person_name, SUM(s.sale_value) AS SaleValue
FROM sale s
JOIN sales_split ss ON ss.sale_id = s.id
JOIN sales_person sp ON sp.id = ss.sales_person_id
GROUP BY sp.id;
At this point, I realize you have an error in your expected results (for this data set). Joe does in fact have a sale value of 70, because sale id 1 (value 20), 2 (value 20), and 4 (value 30) add up to 70. However, I still think this query will help you out more than the one you have.
At this point, you can get the values for each sales_person_id by joining those two subqueries to the sales_person table. I took out the join to sales_person in the subqueries, as it became irrelevant now. It even makes the subqueries a little cleaner:
SELECT sp.person_name, COALESCE(t1.SplitValue, 0) AS SplitValue, COALESCE(t2.SaleValue, 0) AS SaleValue
FROM sales_person sp
LEFT JOIN(
SELECT ss.sales_person_id, SUM(ss.split) AS SplitValue
FROM sales_split ss
GROUP BY ss.sales_person_id) t1 ON t1.sales_person_id = sp.id
LEFT JOIN(
SELECT ss.sales_person_id, SUM(s.sale_value) AS SaleValue
FROM sale s
JOIN sales_split ss ON ss.sale_id = s.id
GROUP BY ss.sales_person_id) t2 ON t2.sales_person_id = sp.id;
Here is an SQL Fiddle example.
EDIT: I understand now why Joe's actual sale price is 50, because he split twice on sale id 1. To work around this, I first got a list of distinct sales for each sales_person like this:
SELECT DISTINCT sale_id, sales_person_id
FROM sales_split;
This way, there is only one row for sales_person_id = 1 and sale_id = 1. Then, it was easy enough to join that to the sale table and get the proper sales value for each sales_person:
SELECT t.sales_person_id, SUM(s.sale_value) AS SaleValue
FROM(
SELECT DISTINCT sale_id, sales_person_id
FROM sales_split) t
JOIN sale s ON s.id = t.sale_id
GROUP BY t.sales_person_id;
The rest of my answer above still fits. I wrote one query to get SplitValue, and one query to get SaleValue, and I joined them together. So, all I have to do now is replace the subquery I just gave you, with the incorrect subquery from further up:
SELECT sp.person_name, COALESCE(t1.SplitValue, 0) AS SplitValue, COALESCE(t2.SaleValue, 0) AS SaleValue
FROM sales_person sp
LEFT JOIN(
SELECT ss.sales_person_id, SUM(ss.split) AS SplitValue
FROM sales_split ss
GROUP BY ss.sales_person_id) t1 ON t1.sales_person_id = sp.id
LEFT JOIN(
SELECT t.sales_person_id, SUM(s.sale_value) AS SaleValue
FROM(
SELECT DISTINCT sale_id, sales_person_id
FROM sales_split) t
JOIN sale s ON s.id = t.sale_id
GROUP BY t.sales_person_id) t2 ON t2.sales_person_id = sp.id;
Here is the updated SQL Fiddle.
You mentioned in the comments that you shortened your data for brevity, which is fine. I am leaving my joins as they are, and I trust that it gives you enough direction that you can adjust them accordingly to match your proper structure.
I have one table called Employee that contains the following information like
ID Name Skills
1 xyz java,php,dotnet
2 abc ruby,java,python
Skills column saves comma seprated values. it could be one or more.
I want to design a query based on OR operate.When user search java, Database displays two employees likes xyz, abc.
I have tried this query but no result comes out:
SELECT m
FROM Employee m
Where m.Skills LIKE '%JAVA% MS PAINT%'
Any Suggestion?
Ideally you should not store the data in a comma-separated list. You should create a join table between the employees and the skills:
CREATE TABLE employees (`e_id` int, `e_name` varchar(3));
INSERT INTO employees (`e_id`, `e_name`)
VALUES
(1, 'xyz'),
(2, 'abc');
CREATE TABLE skills (`s_id` int, `s_name` varchar(6));
INSERT INTO skills (`s_id`, `s_name`)
VALUES
(1, 'java'),
(2, 'php'),
(3, 'dotnet'),
(4, 'ruby'),
(5, 'python');
CREATE TABLE employees_skills (`e_d` int, `s_id` int);
INSERT INTO employees_skills
(`e_d`, `s_id`)
VALUES
(1, 1),
(1, 2),
(1, 3),
(2, 4),
(2, 1),
(2, 5);
Then when you want to select from the tables you will use:
select *
from employees e
inner join employees_skills es
on e.e_id = es.e_id
inner join skills s
on es.s_is = s.s_id
where s.s_name in ('java', 'ruby')
Or you can use the OR clause:
select *
from employees e
inner join employees_skills es
on e.e_id = es.e_id
inner join skills s
on es.s_is = s.s_id
where s.s_name = 'java'
or s.s_name = 'ruby'
use like not good solution. Full scan and slow query.
Create new table with catalog of skills.
Create table user_skills
You should set up your tables like this:
Employee:
ID | Name
---+------
1 | xyz
2 | abc
Skill:
ID | Name
---+------
1 | java
2 | php
3 | dotnet
4 | ruby
5 | python
EmployeeSkills:
ID | EmployeeID | SkillID
---+------------+----------
1 | 1 | 1
2 | 1 | 2
3 | 1 | 3
4 | 2 | 4
5 | 2 | 1
6 | 2 | 5
the query to find employees with skills in java would look like this
SELECT
E.Name
FROM
Employee AS E
INNER JOIN
EmployeeSkill AS ES
ON
ES.EmployeeID = E.ID
INNER JOIN
Skill AS S
ON
ES.SkillID = S.ID
WHERE
S.Name = 'java'
select name from table where skill like '%java%' should do