MySQL table 'Features'
prop_id name
----------------------------
1 Wifi
2 Off Road Parking
1 Off Road Parking
2 Close to beach
3 Close to Pub
1 Close to Pub
Prop_id is the id in another table of the property
what i would like to do is get the id's of all the properties where they have 'Wifi' and 'Close to pub'
so in this case i would like it to only return 1
Hope that i have made sence!
There are several ways to achieve this, one ugly way is:
select prop_id from features
where name = 'Wifi' and prop_id in (
select prop_id from features where name = 'Close to Pub'
)
Use SELECT DISTINCT.
SELECT DISTINCT prop_id FROM table WHERE name="Wifi" or name="Close to pub"
Related
I have a table called Sets for LEGO:
set_number (Primary Key)
set_name
other_fields
123
Firetruck
abc
234
Star Wars
abc
I have another table called Parts for LEGO:
part_number (Primary Key)
name
set_number (references set_number from Sets)
1
Truck Roof
123
2
Truck Body
123
3
Neimoidian Viceroy Robe
234
I want to create another column in the Sets table to indicate the number of unique parts the particular set has.
I was able to output the number of unique parts with the following:
SELECT s.set_number, COUNT(*) AS num_diff_parts
FROM Sets s, Parts p
WHERE p.set_number = s.set_number
GROUP BY s.set_number
This outputs the following table (let's call it results):
set_number
num_diff_parts
123
2
234
1
However, I wonder if I can put the column (num_diff_parts) into the Sets table as a new column, instead of having to run this query every time when I need this information, or create another table just to contain the content of the results table.
Ideally, the Sets table should look like this:
set_number (Primary Key)
set_name
other_fields
num_diff_parts
123
Firetruck
abc
2
234
Star Wars
abc
1
I've also tried to do GROUP BY on multiple fields, but I don't think that's safe to do as those fields can have repeats and will throw off the results.
select distinct
set_number
,set_name
,other_fields
,count(*) over(partition by set_number) as num_diff_parts
from Sets join Parts using(set_number)
set_number
set_name
other_fields
num_diff_parts
123
Firetruck
abc
2
234
Star Wars
abc
1
We can also count() before joining the tables.
with parts_cnt as (
select set_number
,count(*) as num_diff_parts
from Parts
group by set_number
)
select *
from Sets join parts_cnt using(set_number)
Fiddle
However, I wonder if I can put the column (num_diff_parts) into the Sets table as a new column, instead of having to run this query every time when I need this information
I would recommend using a view ; with this technique, the information is always available, and you don’t need to keep it up to date by yourself.
In MySQL, a correlated subquery comes handy to efficiently compute the count of parts per set :
create view v_sets as
select s.*,
(
select count(*)
from parts p
where p.set_number = s.set_number
) num_diff_parts
from sets s
What I'm trying to do is to GetAPersonByID by doing some inner joins from different tables.
TABLE PEOPLE
IDPerson
Name
LastName
E-mail
fk_ID_Skin
1
Example
Explanation
help#please.com
1
2
Example2
Explanation
ineed#somebody.com
2
TABLE SKINS
IDSkin
Name
1
Normal
2
Weird
TABLE PRODUCTS
IDProduct
Name
fk_skin_type
Photo
1
Oil
1
PhotoOil
2
Water
2
PhotoWater
3
Cream
2
PhotoCream
I need to know which products the CUSTOMER should use according to their SKIN TYPE
But... When I tried to do the InnerJoins (My apologies for the Spanish text in the database):
SELECT
people.IDPerson AS 'Id_person',
people.name AS 'Name',
people.lastname AS 'Lastname',
people.email AS 'E-mail',
skins.name AS 'Skin',
products.name AS 'Product',
products.photo AS 'Photo'
FROM
((people
INNER JOIN skins
ON people.fk_ID_skin = skins.IDSkin)
INNER JOIN products
ON people.fk_ID_skin = products.fk_skin_type)
WHERE IDPerson = c_id;
How can I show 'X Person' without repeating the data?
I'm using MySQL Workbench
How can I show 'X Person' without repeating the data?
It sounds like you are saying you want to see only 1 row per person? Assuming that's the case then I think what you are looking to do is GROUP BY IDPerson. Then you could use the GROUP_CONCAT function in your SELECT statement to generate a comma separated list of the values Foto, Producto, etc.
Currently I have two MySQL tables
Properties
id name
1 Grove house
2 howard house
3 sunny side
Advanced options
prop_id name
1 Wifi
1 Enclosed garden
1 Swimming pool
2 Swimming pool
As you can see table two contains specific features about the properties
When I only have max 3 options the query below worked just fine. (maybe a little slow but ok) now things have expanded somewhat and i have a max of 12 options that it is possible to search by and its causing me some major speed issues. The query below is for 8 options and as you can see its very messy. Is there a better way of doing what I'm trying to achieve?
SELECT * FROM properties WHERE id in (
select prop_id from advanced_options where name = 'Within 2 miles of sea or river' and prop_id in (
select prop_id from advanced_options where name = 'WiFi' and prop_id in (
select prop_id from advanced_options where name = 'Walking distance to pub' and prop_id in (
select prop_id from advanced_options where name = 'Swimming pool' and prop_id in (
select prop_id from advanced_options where name = 'Sea or River views' and prop_id in (
select prop_id from advanced_options where name = 'Pet friendly' and prop_id in (
select prop_id from advanced_options where name = 'Open fire, wood burning stove or a real flame fire-place' and prop_id in (
select prop_id from advanced_options where name='Off road parking')
)
)
)
)
)
)
)
Like Mike Brant suggest I would consider altering your datamodel to a limit to set and creating a column for each of these in your properties table. But some times the boss comes: "We also need 'flatscreen tv'" and then you have to go back to the DB and update the scheme and your data access layer.
A way to move this logic somehow out if the database it to use bitwise comparison. This allows you to make simple queries, but requires a bit of preprocessing before you make your query.
Judge for yourself.
I've put everything in a test suite for you here sqlfiddle
The basic idea is that each property in your table has an id that is the power of 2. Like this:
INSERT INTO `advanced_options` (id, name)
VALUES
(1, 'Wifi'),
(2, 'Enclosing Garden'),
(8, 'Swimming Pool'),
(16, 'Grill');
You can then store a single value in your properties table buy adding up the options:
Wifi + Swimming Pool = 1 + 8 = 9
If you want to find all properties with wifi and a swimming pool you then do like this:
SELECT * FROM `properties` WHERE `advanced_options` & 9 = 9
If you just wanted swimming pool this would be it:
SELECT * FROM `properties` WHERE `advanced_options` & 8 = 8
Go try out the fiddle
You really need to consider a schema change to your table. It seems that advanced options in and of themselves don't have any properties, so instead of an advanced_options table that is trying to be a many-to-many JOIN table, why not just have a property_options table with a field for each "options". Something like this
|prop_id | wifi | swimming_pool | etc..
-----------------------------------
| 1 | 0 | 1 |
| 2 | 1 | 0 |
Here each field is a simple TINYINT field with 0/1 boolean representation.
To where you could query like:
SELECT * FROM properties AS p
INNER JOIN property_options AS po ON p.id = po.prop.id
WHERE wifi = 1 AND swimming_pool = 1 ....
Here you would just build your WHERE clause based on which options you are querying for.
There actually wouldn't be any need to even have a separate table, as these records would have a one-to-one relationship with the properties, so you could normalize these fields onto you properties table if you like.
Join back to the advanced_options table multiple times. Here's a sample with 2 (lather, rinse, repeat).
select o1.prop_id
from advanced_options o1
inner join advanced_options o2 on o1.prop_id = o2.prop_id and o2.name = "WiFi"
where o1.name = 'Within 2 miles of sea or river'
Could you do something like this?:
select p.*,count(a.prop_id) as cnt
from properties p
inner join advanced_options a on a.prop_id = p.id
where a.name in ('Enclosed garden','Swimming pool')
group by p.name
having cnt = 2
That query would get all the properties that have ALL of those advanced_options...
I would also suggest normalizing your tables by creating a separate table Called Advanced_option (id,name) where you store your unique Option values and then create a junction entity table like Property_x_AdvancedOption (fk_PropertyID, FK_AdvancedOptionID) that way you use less resources and avoid data integrity issues.
I have two tables.
Table Emp
id name
1 Ajay
2 Amol
3 Sanjay
4 Vijay
Table Sports
Sport_name Played by
Cricket ^2^,^3^,^4^
Football ^1^,^3^
Vollyball ^4^,^1^
Now I want to write a query which will give me output like
name No_of_sports_played
Ajay 2
Amol 1
Sanjay 2
Vijay 2
So what will be Mysql query for this?
I agree with the above answers/comments that you are not using a database for what a database is for, but here is how you could calculate your table from your current structure in case you have no control over that:
SELECT Emp.name, IF(Played_by IS NULL,0,COUNT(*)) as Num_Sports
FROM Emp
LEFT JOIN Sports
ON Sports.Played_by RLIKE CONCAT('[[:<:]]',Emp.id,'[[:>:]]')
GROUP BY Emp.name;
See it in action here.
UPDATE: added the IF(Played_by IS NULL,0,COUNT(*)) instead of COUNT(*). This means that if an employee doesn't play anything they'll have a 0 as their Num_Sports. See it here (I also added in those ^ characters and it still works.
What it does is joins the Emp table to the Sports table if it can find the Emp.id in the corresponding Played_by column.
For example, if we wanted to see what sports Ajay played (id=1), we could do:
SELECT *
FROM Emp, Sports
WHERE Sports.Played_by LIKE '%1%'
AND Emp.id=1;
The query I gave as my solution is basically the query above, with a GROUP BY Emp.name to perform it for each employee.
The one modification is the use of RLIKE instead of LIKE.
I use RLIKE '[[:<:]]employeeid[[:>:]]' instead of LIKE '%employeeid%. The [[:<:]] symbols just mean "make sure the employeeid you match is a whole word".
This prevents (e.g.) Emp.id 1 matching the 1 in the Played_by of 3,4,11,2.
You do not want to store your relationships in a column like that. Create this table:
CREATE TABLE player_sports (player_id INTEGER NOT NULL, sport_id INTEGER NOT NULL, PRIMARY KEY(player_id, sport_id));
This assumes you have an id column in your sports table. So now a player will have one record in player_sports for each sport they play.
Your final query will be:
SELECT p.name, COUNT(ps.player_id)
FROM players p, player_sports ps
WHERE ps.player_id = p.id
GROUP BY p.name;
I need to query two tables like this...
table one
customers
id companyname phone
1 | microsoft | 888-888-8888
2 | yahoo | 588-555-8874
3 | google | 225-558-4421
etc...
table two
contacts
id companyid name phone
1 | 1 | sam | 558-998-5541
2 | 1 | john | 558-998-1154
3 | 3 | larry | 111-145-7885
4 | 3 | dave | 558-998-5254
5 | 2 | sam | 558-997-5421
I need to query both tables.
So if I search for sam
it should return a list of companies with the contacts
microsoft 888-888-8888
sam 558-998-5541
john 558-998-1154
yahoo 588-555-8874
sam 558-997-5421
so it returns all company with sam and all contacts with it....
same is if I would search 'microsoft' it should return without yahoo
microsoft 888-888-8888
sam 558-998-5541
john 558-998-1154
and if I search "558-998-1154" it should return like this...
microsoft 888-888-8888
sam 558-998-5541
john 558-998-1154
I hope this is clear....
Here is my current query:
SELECT * FROM
customers, customer_contacts
WHERE (customers.code LIKE '%#URL.qm1#%'
or customers.COMPANY LIKE '%#URL.qm1#%'
or customers.phone LIKE '%#URL.qm1#%'
or customers.contact LIKE '%#URL.qm1#%'
or customers.name LIKE '%#URL.qm1#%'
or customers.address1 LIKE '%#URL.qm1#%')
AND (customers.id = customer_contacts.cid
and customer_contacts.deleted = 0)
this returns only those who have a contact...
I would need
it to return the ones without contacts as well.
This is a sticky problem, one that I almost want to say "don't try to do this is one query".
I approach SQL queries like this from a programming perspective, as I feel the results tend to be less "magical". (A property I see in too many queries — it seems SQL queries these days are written using monkeys at keyboards…)
Figure out which company IDs we want to list. This is the union of these two things:
Any "people" results matched on name or number
Any "company" results matched on name or number
List out the number for that company, and the people as well.
Let's do #2 first:
SELECT
companyname AS name,
phone
FROM
customers
WHERE id IN (company_ids we want)
UNION
SELECT
name, phone
FROM
contacts
WHERE companyid IN (company_ids we want)
Since "company_ids we want" is going to be a query, rearrange this to boil it down to just 1 occurrence:
SELECT
name, phone
FROM
(
SELECT
id AS companyid,
companyname AS name,
phone
FROM
customers
UNION
SELECT companyid, name, phone FROM contacts
) AS entities
WHERE
companyid IN (company_ids we want)
Now, to fill in the fun part, we need to answer #1:
Part #1.1 is:
SELECT companyid FROM contacts WHERE name = $search OR number = $search;
Part #1.2 is:
SELECT id AS companyid FROM customers WHERE companyname = $search OR number = $search;
(Note that $search is our input — parameterized queries differ greatly from one SQL vendor to the next, so replace that syntax as needed.)
Put the UNION of those two in the IN, and we're done:
SELECT
name, phone
FROM
(
SELECT
id AS companyid,
companyname AS name,
phone
FROM
customers
UNION
SELECT companyid, name, phone FROM contacts
) AS entities
WHERE
companyid IN (
SELECT companyid FROM contacts WHERE name = $search OR phone = $search
UNION
SELECT id AS companyid FROM customers WHERE companyname = $search OR phone = $search
)
;
And pray the database can figure out a query plan that performs this in a reasonable amount of time. Sure you don't want to roundtrip to the DB a few times?
Note the methodology: We determined what we wanted ("the names/phones for customers/contacts matching certain companyids") and then figured out the missing piece ("which company ids?"). This comes from the fact that once you match a particular person in a company (say, sam), you want everyone from that company, plus the company, or everything with that company ID. Knowing that, we get our outer query (#2), and then we just need to figure out how to determine which companies we're interested in.
Note that these won't (and SQL queries, without an ORDER BY don't) give the queries back in your rather fancy order. You can add a helper column to the inner query, however, and accomplish this:
SELECT
name, phone
FROM
(
SELECT
0 AS is_person,
id AS companyid,
companyname AS name,
phone
FROM
customers
UNION
SELECT 1 AS is_person, companyid, name, phone FROM contacts
) AS entities
WHERE
companyid IN (
SELECT companyid FROM contacts WHERE name = $search OR phone = $search
UNION
SELECT id AS companyid FROM customers WHERE companyname = $search OR phone = $search
)
ORDER BY
companyid, is_person, name
;
You can also use the is_person column (if you add it to the SELECT) if you need to segment the results in whatever gets this query's results.
(And if you end up using queries of this length, please, for the love of God, -- comment them!)