i need help on this. I don't know how to use join in mysql so I try this to avoid to use join.
I have to have in the end this type of table:
tracce.titolo - data - aka (where tracce.idma=artist.id) - aka (for featuring. so i need to achive ida, that's id that identify the featured artist, and i do this under this condition feat.idt=tracce.id (so where the id from the track is the same for the id of the track in the feat table) and where artist.id=feat.ida (so where the id that identify the artist in feat table is the same of the one in the table of artists)).
I try this but it not work, that's the code:
SELECT tracce.titolo, tracce.data, artist.aka, feat.ida FROM tracce, artist, feat
WHERE tracce.idma=artist.id AND feat.idt=tracce.id
SELECT artist.aka FROM tracce
WHERE artist.id=feat.ida
Table structure is:
artist: id - aka
tracce: id - titolo - idma - data (id of track, titolo is title of the track, idma is the id of the main artist and data is date)
feat: idt - ida (idt is the id of the track and ida is the id of the featured artist)
EDIT: modify the code made by Christian, I solve adding another join on artist table using two different alias and it seems to work.
SELECT tracce.titolo, tracce.data, a1.aka as 'main', a2.aka as 'feat' from tracce
JOIN artist a1
ON tracce.idma = a1.id
JOIN feat
ON feat.idt = tracce.id
JOIN artist a2
ON a2.id = feat.ida
What you had in the first statement is an implicit join - not recommended as it will become obsolete. Not exactly sure if I understood, but perhaps this is what you're looking for?
SELECT tracce.titolo, tracce.data, artist.aka, feat.ida from tracce
JOIN artist
ON tracce.idma = artist.id
JOIN feat
ON feat.idt = tracce.id AND artist.id = feat.ida
I am using table aliases to make code shorter.
Related
Probably bad title, but I could not find better short description.
These are the tables Im working with:
Table Objects:
ID
NAME
Table Geo:
ID
NAME
PARENT_ID (int)
IDENTIFIER (varchar)
Table ObjectsGeo:
ID
OBJECT_ID
GEO_ID
So I insert some data in "objects":
insert into objects values(1,'Jack');
insert into objects values(2,'Penny');
And then in "geo":
insert into geo values(1,'USA', null, '001');
insert into geo values(2,'New York', 1, '1001');
insert into geo values(3,'England', null, '002');
insert into geo values(4,'London', 3, '1002');
If Jack lives in New York, then I will insert it this way:
insert into ObjectsGeo values(1,1,1);
insert into ObjectsGeo values(2,1,2);
If you tell me this is a bad database design, I will agree (somebody else coded this). However, this is what I have now and making changes in the design could be complicated/cause bugs somewhere else.
Now, when I need to fetch Jack from database, as I also want to know where he lives, I do something quite ugly, which is having a left join to also include "ObjectsGeo". I then only take the first row (sigh) and "manually" put city and country in the object with programming code.
Is there a way, with only one query, to get the row for Jack including 2 fields, one for country and one for city?
----EDIT----
The tables were more or less pseudocode. The query itself (also as pseudocode) should be:
select o.*, g.identifier from objects o left join ObjectsGeo og on og.object_id = o.id left join Geo g on g.id = og.geo_id where o.id = 1;
Following query will get the job done:
select o.name,
(select name from geo where id = min(og.geo_id)) as geo_country,
(select name from geo where id = max(og.geo_id)) as geo_city
from objects o
inner join objectsgeo og
on og.object_id = o.id
inner join geo g
on g.id = og.geo_id
group by og.object_id;
Click here for Demo
If you've any doubt(s), feel free to ask by commenting below.
Hope it helps!
I need to write query that joins several tables and I need distinct value from one table based on max count().
These are my tables names and columns:
bands:
db|name|
releases_artists:
release_db|band_db
releases_styles
release_db|style
Relations between tables are (needed for JOINs):
releases_artists.band_db = bands.db
releases_styles.release_db = releases_artists.release_db
And now the query that I need to write:
SELECT b.name, most_common_style
LEFT JOIN releases_artists ra ON ra.band_db = b.db
and here I need to find the most common style from all band releases
JOIN(
SELECT DISTINCT style WHERE releases_styles.release_db = ra.release_db ORDER BY COUNT() DESC LIMIT 1
)
FROM bands b
WHERE b.name LIKE 'something'
This is just a non working example of what I want to accomplish. It would be great if someone could help me build this query.
Thanks in advance.
EDIT 1
Each artist from table bands can have multiple records from releases_artists table based on band_db and each release can have multiple styles from releases_styles based on release_db
So if I search for b.name LIKE '%ray%' it returns something similar to:
`bands`:
o7te|Ray Wilson
9i84|Ray Parkey Jr.
`releases_artists` for Ray Wilson:
tv5c|o7te (for example album `Change`)
78wz|o7te (`The Next Best Thing`)
nz7c|o7te (`Propaganda Man`)
`releases_styles`
tv5c|Pop
tv5c|Rock
tv5c|Alternative Pop/Rock
----
78wz|Rock
78wz|Pop
78wz|Classic Rock
I need style name that repeats mostly from all artist releases as this artist main style.
Ok, this is a bit of a hack. But the only alternatives I could think of involve heaps of nested subqueries. So here goes:
SELECT name
, SUBSTRING_INDEX(GROUP_CONCAT(style ORDER BY release_count DESC SEPARATOR '|'), '|', 1) AS most_common_style
FROM (
SELECT b.db
, b.name
, rs.style
, COUNT(*) AS release_count
FROM bands b
JOIN releases_artists ra ON ra.band_db = b.db
JOIN releases_styles rs ON rs.release_db = ra.release_db
GROUP BY b.db, rs.style
) s
GROUP BY db;
I need some help about optimal structuring of SQL query. I have model like this:
I'm trying some kind of join between tables NON_NATURAL_PERSON and NNP_NAME. Because I have many names in table NNP_NAME for one person I can't do one-to-one SELECT * from NON_NATURAL_PERSON inner join NNP_NAME etc. That way I'll get extra rows for every name one person has.
Data in tables:
How to extend this query to get rows marked red on picture shown below? My wannabe query criteria is: Always join name of typeA only if exists. If not, join name of typeB. If neither exists join name of typeC.
SELECT nnp.ID, name.NAME, name.TYPE
FROM NON_NATURAL_PERSON nnp
INNER JOIN NNP_NAME name ON (name.NON_NATURAL_PERSON = nnp.ID)
If type is spelled exactly as it's written (typeA, typeB, typeC) then you can use MIN() function:
SELECT NON_NATURAL_PERSON, MIN(type) AS min_type
FROM NNP_NAME
GROUP BY NON_NATURAL_PERSON
if you also want the username you can use this query:
SELECT
n1.NON_NATURAL_PERSON AS ID,
n1.Name,
n1.Type
FROM
NNP_NAME n1 LEFT JOIN NNP_NAME n2
ON n1.NON_NATURAL_PERSON = n2.NON_NATURAL_PERSON
AND n1.Type > n2.type
WHERE
n2.type IS NULL
Please see this fiddle. If Types are not literally sorted, change this line:
AND n1.Type > n2.type
with this:
AND FIELD(n1.Type, 'TypeA', 'TypeB', 'TypeC') >
FIELD(n2.type, 'TypeA', 'TypeB', 'TypeC')
MySQL FIELD(str, str1, str2, ...) function returns the index (position) of str in the str1, str2, ... list, and 0 if str is not found. You want to get the "first" record, ordered by type, for every NON_NATURAL_PERSON. There are multiple ways to get this info, I chose a self join:
ON n1.NON_NATURAL_PERSON = n2.NON_NATURAL_PERSON
AND n1.Type > n2.type -- or filed function
with the WHERE condition:
WHERE n2.type IS NULL
this will return all rows where the join didn't succeed - the join won't succeed when there is not n2.type that is less than n1.type - it will return the first record.
Edit
If you want a platform independent solution, avoiding the creation of new tables, you could use CASE WHEN, just change
AND n1.Type > n2.Type
with
AND
CASE
WHEN n1.Type='TypeA' THEN 1
WHEN n1.Type='TypeB' THEN 2
WHEN n1.Type='TypeC' THEN 3
END
>
CASE
WHEN n2.Type='TypeA' THEN 1
WHEN n2.Type='TypeB' THEN 2
WHEN n2.Type='TypeC' THEN 3
END
There is a piece of information missing. You say:
Always join name of typeA only if exists. If not, join name of typeB. If neither exists join name of typeC.
But you do not indicate why you prefer typeA over typeB. This information is not included in your data.
In the answer of #fthiella, either lexicographical is assumed, or an arbitrary order is given using FIELD. This is also the reason why two joins with the table nnp_name is necessary.
You can solve this problem by adding a table name_type (id, name, order) and changing the type column to contain the id. This will allow you to add the missing information in a clean way.
With an additional join with this new table, you will be able get the preferred nnp_name for each row.
I am trying to join the following tables with the following code, but I can't join the last columns.
Table:magazine
id_mag **mag_name** id_freq
Table:frequency
id_freq **freq_name**
Table:copy
id_mag **id_copy** **copy_date** copy_price copy_page_number
Table:article
id_art **art_name** **art_page_number**
Table:copy_art
id_mag **id_copy** id_art article_page_num
I want to show a table with the following columns. The columns in the tables magazine, frequency, copy, article & copy_art that have ** ** are the ones I am interested in to be showed:
mag_name freq_name id_copy copy_date art_name art_page_number
I got the following table with this code:
SELECT * FROM magazine
JOIN frequency ON magazine.id_freq = frequency.id_freq
JOIN copy_art ON revista.id_mag=copy_art.id_mag
JOIN article ON copy_art.id_art=article.id_art
JOIN copy ON copy_art.id_copy=copy.id_copy;
Here is the translation for the name of each column that appears in the image:
id_rev = id_mag
nom_rev = mag_name
id_frec = id_freq
nom_frec = freq_name
id_rev = id_mag
id_ejem = id_copy
id_art = id_art
num_pag = article_page_num
nom_art = art_name
num_pag_art = art_page_number
fecha_ejem = copy_date
precio = copy_price
My doubt is the following:
What should I do in order to have the table with?
mag_name freq_name id_copy copy_date art_name article_page_num
Thanks a lot for your kindly support!
If you only want a few columns in the output, then you have to list which columns you do want. The key structure of the data is unclear (meaning it isn't clear which columns are the primary keys of each table); you have the id_mag and id_copy columns both appearing in copy and copy_art and it isn't entirely clear whether they're a composite key or id_copy is sufficient. Given that we don't have that information, we'll have to take your SELECT statement and its joins as gospel, but I'm not convinced that's correct.
You wrote:
SELECT *
FROM magazine
JOIN frequency ON magazine.id_freq = frequency.id_freq
JOIN copy_art ON revista.id_mag=copy_art.id_mag
JOIN article ON copy_art.id_art=article.id_art
JOIN copy ON copy_art.id_copy=copy.id_copy;
This collects all the columns from all the tables mentioned, which is wasteful. So, you need to specify which columns you do want:
SELECT m.mag_name, f.freq_name, c.id_copy, c.copy_date, a.art_name, a.art_page_number
FROM magazine AS m
JOIN frequency AS f ON m.id_freq = f.id_freq
JOIN copy_art AS y ON m.id_mag = y.id_mag
JOIN article AS a ON y.id_art = a.id_art
JOIN copy AS c ON y.id_copy = c.id_copy;
I'm not entirely sure that you need the copy_art table in the query, but I'm assuming you know your data better than I do.
You have to make sure that one of the first tables has got a foreign key for the articulo table to join that as well.
If you add that (For example in the revista table), you can make a JOIN over all tables with something like this:
SELECT * FROM revista
JOIN frecuencia ON revista.id_frec = frecuencia.id_frec
JOIN ejemplar ON revista.id_rev = ejemplar.id_rev
JOIN articulo ON revista.id_art = articulo.id_art;
See this fiddle for an example (I query * here, you can change that to just the columns that you need).
How I can select name of creator and editor from users table, creator and editor are different ids in same table, but user table is different table
Is it what you mean?
$sql = "
SELECT id,name
FROM users
WHERE users.id = editors_table.$editor_id
OR users.id = creators_table.$creator_id";
from what i understand, are you saying you have 3 tables - 1 with creator data, 1 with editor data, and a third that references a record in each of the tables using an id?
if so, you'll have to use JOINs to achieve what you want - something like:
SELECT id, name, editors_table.editor_id, creators_table.creator_id
FROM users
LEFT JOIN editors_table ON user.editor_id = editor_table.editor_id
LEFT JOIN creators_table ON user.creator_id = creator_table.creator_id
WHERE editor_table.editor_id = $editor_id_var
OR creator_table.creator_id = $creator_id_var
(you'll want to go through the query as I'm guessing here)