I am new to JOINS and testing my query, but it's just not working for me...
The situation:
The database has got the following columns:
links (contains unique data)
cl_link (contains the relation between links & cats)
cats (cat. descriptions
images (contains multiple images of one link)
cfvalues (contains the values of the multiple custom fiels
customfields (contains the multiple customfields)
I am using the following query, but the Joins are not working for me. Because I only get one image while sometimes there are multiple. And I only get one customfield instead of multiple and I get none cfvalues.
I guess something is wrong with the JOINS, but I am not sure. Can somebody help me out here?
The SQL
SELECT DISTINCT
rqypj_mt_links.link_name,
rqypj_mt_links.link_desc,
rqypj_mt_links.address,
rqypj_mt_links.city,
rqypj_mt_links.state,
rqypj_mt_links.country,
rqypj_mt_links.postcode,
rqypj_mt_links.telephone,
rqypj_mt_links.fax,
rqypj_mt_links.email,
rqypj_mt_links.website,
rqypj_mt_links.price,
rqypj_mt_links.lat,
rqypj_mt_links.lng,
rqypj_mt_links.zoom,
rqypj_mt_cats.cat_name,
rqypj_mt_images.filename,
rqypj_mt_cfvalues.value,
rqypj_mt_customfields.caption
FROM rqypj_mt_links
LEFT JOIN rqypj_mt_cl
ON rqypj_mt_links.link_id = rqypj_mt_cl.link_id
LEFT JOIN rqypj_mt_cats
ON rqypj_mt_cl.cat_id = rqypj_mt_cats.cat_id
LEFT JOIN rqypj_mt_images
ON rqypj_mt_links.link_id = rqypj_mt_images.link_id
LEFT JOIN rqypj_mt_cfvalues
ON rqypj_mt_links.link_id = rqypj_mt_cfvalues.link_id
LEFT JOIN rqypj_mt_customfields
ON rqypj_mt_customfields.cf_id = rqypj_mt_customfields.cf_id LIMIT 100
Thanks in advance!
Jelte
your last condition doesn't look right:
on rqypj_mt_customfields.cf_id = rqypj_mt_customfields.cf_id
translates to 1=1
Shouldn't it be:
on rqypj_mt_customfields.cf_id = rqypj_mt_cfvalues.cf_id
Probably because you don't have an order by and are using limit.
Change it to
order by rqypj_mt_links.link_id, rqypj_mt_cl.cat_id
limit 100
and then your multiple pictures for the same link should be together.
Also please consider use of alias to make your code easier to read:
SELECT DISTINCT
links.link_name,
links.link_desc,
links.address,
links.city,
links.state,
links.country,
links.postcode,
links.telephone,
links.fax,
links.email,
links.website,
links.price,
links.lat,
links.lng,
links.zoom,
cats.cat_name,
images.filename,
cfvalues.value,
--custom.caption
FROM rqypj_mt_links links
LEFT JOIN rqypj_mt_cl cl ON links.link_id = cl.link_id
LEFT JOIN rqypj_mt_cats cats ON cl.cat_id = cats.cat_id
LEFT JOIN rqypj_mt_images images ON links.link_id = images.link_id
LEFT JOIN rqypj_mt_cfvalues cfvalues ON links.link_id = cfvalues.link_id
--LEFT JOIN rqypj_mt_customfields custom ON custom.cf_id = custom.cf_id
ORDER BY links.link_id, cats.cat_id
LIMIT 100
Related
I have the following SQL string which tries to combine an INNER JOIN with a LEFT JOIN in the FROM section.
As you can see I use table VIP_APP_VIP_SCENARIO_DETAIL_LE to perform the query. When I use it against this table, Access give me an "Invalid Operation" error.
Interestingly, when I use the EXACT same query using the VIP_APP_VIP_SCENARIO_DETAIL_BUDGET or VIP_APP_VIP_SCENARIO_DETAIL_ACTUALS table, it performs flawlessly.
So why would it work on two tables but not the other? All fields are in all tables and the data types are correct.
As a side note: on the query with the error, if I change the LEFT JOIN to an INNER JOIN, it runs with no problem! I really need a LEFT JOIN though.
SELECT
D.MATERIAL_NUMBER,
D.MATERIAL_DESCRIPTION,
D.PRODUCTION_LOT_SIZE,
D.STANDARDS_NAME,
D.WORK_CENTER,
S.OP_SHORT_TEXT,
S.OPERATION_CODE,
D.LINE_SPEED_UPM,
D.PERCENT_STD,
D.EQUIPMENT_SU,
D.EQUIPMENT_CU,
D.OPERATOR_NUM,
V.COSTING_LOT_SIZE,
V.VOL_TOTAL_ADJ
FROM
([STDS_SCENARIO: TEST] AS D INNER JOIN MASTER_SUMMARY AS S ON
D.MATERIAL_NUMBER = S.MATERIAL_NUMBER AND D.WORK_CENTER = S.WORK_CENTER)
LEFT JOIN
(SELECT ITEM_CODE, COSTING_LOT_SIZE, VOL_TOTAL_ADJ
FROM
VIP_APP_VIP_SCENARIO_DETAIL_LE
WHERE SCENARIO_ID = 16968) AS V ON D.MATERIAL_NUMBER = V.ITEM_CODE
ORDER BY D.MATERIAL_NUMBER, D.STANDARDS_NAME, S.OPERATION_CODE;
tried to mock this up in SQL server with some tables of my own, but the structure seemed to work, this follows the pattern referenced above. (hopefully no syntax errors left here)
SELECT * FROM (
select
D.MATERIAL_NUMBER,
D.MATERIAL_DESCRIPTION,
D.PRODUCTION_LOT_SIZE,
D.STANDARDS_NAME,
D.WORK_CENTER,
S.OP_SHORT_TEXT,
S.OPERATION_CODE,
D.LINE_SPEED_UPM,
D.PERCENT_STD,
D.EQUIPMENT_SU,
D.EQUIPMENT_CU,
D.OPERATOR_NUM
FROM [STDS_SCENARIO: TEST] D
INNER JOIN MASTER_SUMMARY S
ON D.MATERIAL_NUMBER = S.MATERIAL_NUMBER AND D.WORK_CENTER = S.WORK_CENTER) AS J
LEFT JOIN
(SELECT ITEM_CODE, COSTING_LOT_SIZE, VOL_TOTAL_ADJ
FROM
VIP_APP_VIP_SCENARIO_DETAIL_LE
WHERE SCENARIO_ID = 16968) AS V ON J.MATERIAL_NUMBER = V.ITEM_CODE
ORDER BY J.MATERIAL_NUMBER, J.STANDARDS_NAME, J.OPERATION_CODE;
Had help from a friend and we discovered that it was a casting problem between a linked Oracle table and the Access table. To fix the problem we casted both sides of the linked fields to a string:
CSTR(D.[MATERIAL_NUMBER]) = CSTR(V.[ITEM_CODE])
I made a query and wanted to not have any duplicates but i got some times 3 duplicates and when i used DISTINCT or DISTINCTROW i got only 2 duplicates.
SELECT f.flight_code,
f.status,
a.airport_name,
a1.airport_name,
f.departing_date+f.departing_time AS SupposedDepartingTime,
f.landing_date+f.landing_time AS SupposedLandingTime,
de.actual_takeoff_date+de.actual_takeoff_time AS ActualDepartingTime,
SupposedLandingTime+(ActualDepartingTime-SupposedDepartingTime) AS ActualLandingTime
FROM
(((Flights AS f
LEFT JOIN Aireports AS a
ON a.airport_code = f.depart_ap)
LEFT JOIN Aireports AS a1
ON f.target_ap = a1.airport_code)
LEFT JOIN Irregular_Events AS ie
ON f.flight_code = ie.flight_code)
LEFT JOIN Delay_Event AS de
ON ie.IE_code = de.delay_code;
had to use LEFT JOIN because when i used INNER JOIN i missed some of the things i wanted to show because i wanted to see all the flights and not only the flights that got delayed or canceled.
This is the results when i used INNER JOIN, you can see only the flights that have the status "ביטול" or "עיכוב" and that is not what i wanted.
[the results with LEFT JOIN][2]
[2]: https://i.stack.imgur.com/cgE2G.png
and when i used DISTINCT where you see the rows with the NUMBER 6 on the first column it appear only two times
IMPORTANT!
I just checked my query and all the tables i use there and i saw my problem but dont know how to fix it!
in the table Irregular_Events i have more the one event for flights 3,6 and 8 and that is why when i use LEFT JOIN i see more even thou i use distinct, please give me some help!
Not entirely sure without seeing the table structure, but this might work:
SELECT f.flight_code,
f.status,
a.airport_name,
a1.airport_name,
f.departing_date+f.departing_time AS SupposedDepartingTime,
f.landing_date+f.landing_time AS SupposedLandingTime,
de.actual_takeoff_date+de.actual_takeoff_time AS ActualDepartingTime,
SupposedLandingTime+(ActualDepartingTime-SupposedDepartingTime) AS ActualLandingTime
FROM
((Flights AS f
LEFT JOIN Aireports AS a
ON a.airport_code = f.depart_ap)
LEFT JOIN Aireports AS a1
ON f.target_ap = a1.airport_code)
LEFT JOIN
(
SELECT
ie.flight_code,
de1.actual_takeoff_date,
de1.actual_takeoff_time
FROM
Irregular_Events ie
INNER JOIN Event AS de1
ON ie.IE_code = de1.delay_code
) AS de
ON f.flight_code = de.flight_code
It is hard to tell what is the problem with your query without any sample of the output, and without any description of the structure of your tables.
But your problem is that your are querying from the flights table, which [I assume] can be linked to multiple irregular_events, which can possibly also be linked to multiple delay_event.
If you want to get only one row per flight, you need to make sure your joins return only one row too. Maybe you can do it by adding one more condition to the join, or by adding a condition in a sub-query.
EDIT
You could try to add a GROUP BY to the query:
GROUP BY
f.flight_code,
f.status,
a.airport_name,
a1.airport_name;
I'm trying to retrieve a list of components via my computer_system, BUT if a computer system's graphics card is set to null (I.e. It has an onboard), the row isn't returned by my select statement.
I've been trying to use COALESCE without results. I've also tried with and OR in my WHERE clause, which then just returns my computer system with all different kinds of graphic cards.
Relevant code:
SELECT
computer_system.cs_id,
computer_system.cs_name,
motherboard.name,
motherboard.price,
cpu.name,
cpu.price,
gfx.name,
gfx.price
FROM
public.computer_case ,
public.computer_system,
public.cpu,
public.gfx,
public.motherboard,
public.ram
WHERE
computer_system.cs_ram = ram.ram_id AND
computer_system.cs_cpu = cpu.cpu_id AND
computer_system.cs_mb = motherboard.mb_id AND
computer_system.cs_case = computer_case.case_id AND
computer_system.cs_gfx = gfx.gfx_id; <-- ( OR computer_system.cs_gfx IS NULL)
Returns:
1;"Computer1";"Fractal Design"; 721.00; "MSI Z87"; 982.00; "Core i7 I7-4770K "; 2147.00; "Crucial Gamer"; 1253.00; "ASUS GTX780";3328.00
Should I use Joins? Is there no easy way to say return the requested row, even if there's a bloody NULL value. Been struggling with this for at least 2 hours.
Tables will be posted if needed.
EDIT: It should return a second row:
2;"Computer2";"Fractal Design"; 721.00; "MSI Z87"; 982.00; "Core i7 I7-4770K "; 2147.00; "Crucial Gamer"; 1253.00; "null/nothing";null/nothing
You want a LEFT OUTER JOIN.
First, clean up your code so you use ANSI joins so it's readable:
SELECT
computer_system.cs_id,
computer_system.cs_name,
motherboard.name,
motherboard.price,
cpu.name,
cpu.price,
gfx.name,
gfx.price
FROM
public.computer_system
INNER JOIN public.computer_case ON computer_system.cs_case = computer_case.case_id
INNER JOIN public.cpu ON computer_system.cs_cpu = cpu.cpu_id
INNER JOIN public.gfx ON computer_system.cs_gfx = gfx.gfx_id
INNER JOIN public.motherboard ON computer_system.cs_mb = motherboard.mb_id
INNER JOIN public.ram ON computer_system.cs_ram = ram.ram_id;
Then change the INNER JOIN on public.gfx to a LEFT OUTER JOIN:
LEFT OUTER JOIN public.gfx ON computer_system.cs_gfx = gfx.gfx_id
See PostgreSQL tutorial - joins.
I very strongly recommend reading an introductory tutorial to SQL - at least the PostgreSQL tutorial, preferably some more material as well.
It looks like it's just a bracket placement issue. Pull the null check and the graphics card id comparison into a clause by itself.
...
computer_system.cs_case = computer_case.case_id AND
(computer_system.cs_gfx IS NULL OR computer_system.cs_gfx = gfx.gfx_id)
Additionally, you ask if you should use joins. You are in fact using joins, by virtue of having multiple tables in your FROM clause and specifying the join criteria in the WHERE clause. Changing this to use the JOIN ON syntax might be a little easier to read:
FROM sometable A
JOIN someothertable B
ON A.somefield = B.somefield
JOIN somethirdtable C
ON A.somefield = C.somefield
etc
Edit:
You also likely want to make the join where you expect the null value to be a left outer join:
SELECT * FROM
first_table a
LEFT OUTER JOIN second_table b
ON a.someValue = b.someValue
If there is no match in the join, the row from the left side will still be returned.
I have a SQL query with many left joins
SELECT COUNT(DISTINCT po.o_id)
FROM T_PROPOSAL_INFO po
LEFT JOIN T_PLAN_TYPE tp ON tp.plan_type_id = po.Plan_Type_Fk
LEFT JOIN T_PRODUCT_TYPE pt ON pt.PRODUCT_TYPE_ID = po.cust_product_type_fk
LEFT JOIN T_PROPOSAL_TYPE prt ON prt.PROPTYPE_ID = po.proposal_type_fk
LEFT JOIN T_BUSINESS_SOURCE bs ON bs.BUSINESS_SOURCE_ID = po.CONT_AGT_BRK_CHANNEL_FK
LEFT JOIN T_USER ur ON ur.Id = po.user_id_fk
LEFT JOIN T_ROLES ro ON ur.roleid_fk = ro.Role_Id
LEFT JOIN T_UNDERWRITING_DECISION und ON und.O_Id = po.decision_id_fk
LEFT JOIN T_STATUS st ON st.STATUS_ID = po.piv_uw_status_fk
LEFT OUTER JOIN T_MEMBER_INFO mi ON mi.proposal_info_fk = po.O_ID
WHERE 1 = 1
AND po.CUST_APP_NO LIKE '%100010233976%'
AND 1 = 1
AND po.IS_STP <> 1
AND po.PIV_UW_STATUS_FK != 10
The performance seems to be not good and I would like to optimize the query.
Any suggestions please?
Try this one -
SELECT COUNT(DISTINCT po.o_id)
FROM T_PROPOSAL_INFO po
WHERE PO.CUST_APP_NO LIKE '%100010233976%'
AND PO.IS_STP <> 1
AND po.PIV_UW_STATUS_FK != 10
First, check your indexes. Are they old? Did they get fragmented? Do they need rebuilding?
Then, check your "execution plan" (varies depending on the SQL Engine): are all joins properly understood? Are some of them 'out of order'? Do some of them transfer too many data?
Then, check your plan and indexes: are all important columns covered? Are there any outstandingly lengthy table scans or joins? Are the columns in indexes IN ORDER with the query?
Then, revise your query:
- can you extract some parts that normally would quickly generate small rowset?
- can you add new columns to indexes so join/filter expressions will get covered?
- or reorder them so they match the query better?
And, supporting the solution from #Devart:
Can you eliminate some tables on the way? does the where touch the other tables at all? does the data in the other tables modify the count significantly? If neither SELECT nor WHERE never touches the other joined columns, and if the COUNT exact value is not that important (i.e. does that T_PROPOSAL_INFO exist?) then you might remove all the joins completely, as Devart suggested. LEFTJOINs never reduce the number of rows. They only copy/expand/multiply the rows.
I'm trying to run this query:
SELECT
Destaque.destaque, Noticia.id, Noticia.antetitulo,
Noticia.titulo, Noticia.lead, Noticia.legenda,
Noticia.publicacao, Seccao.descricao, Album.pasta,
Foto.ficheiro, Foto.descricao, Cronista.nome,
Cronista.profissao, Cronista.ficheiro,
AudioFile.*, AudioCollection.*, VideoFile.*, VideoCollection.*
FROM
nt_highlights AS Destaque
LEFT JOIN nt_noticias AS Noticia ON Destaque.noticia_id = Noticia.id
LEFT JOIN mm_fotos AS Foto ON Noticia.foto_id = Foto.id
LEFT JOIN nt_temas AS Seccao ON Noticia.tema_id = Seccao.id
LEFT JOIN mm_albuns AS Album ON Foto.album_id = Album.id
LEFT JOIN nt_cronistas AS Cronista ON Cronista.id = Noticia.cronista_id
LEFT JOIN ntNoticias_mmFiles AS Rel ON Rel.noticia_id = Noticia.id
LEFT JOIN mm_files AS AudioFile ON AudioFile.id = Rel.file_id
LEFT JOIN mm_coleccoes AS AudioCollection ON AudioFile.coleccao_id = AudioCollection.id
LEFT JOIN mm_files AS VideoFile ON VideoFile.id = Rel.file_id
LEFT JOIN mm_coleccoes AS VideoCollection ON VideoFile.coleccao_id = VideoCollection.id
WHERE
Destaque.area_id = 1
AND Noticia.paraPublicacao = 1
AND Noticia.publicacao <= NOW()
AND (AudioFile.mimeType != '' OR AudioFile.id IS NULL)
AND (VideoFile.mimeType = '' OR VideoFile.id IS NULL)
ORDER BY
Destaque.destaque
This will get me a number of articles (from nt_noticias) and the idea is to get at the same time a Video and an Audio file from the mm_files table.
What happens is that when I have an article with a sound and a video, MySQL will return 4 rows:
with the sound (video is null)
with the video (sound is null)
with all nulls
with the sound AND the video
How can I "force" it to return just one row per article with any existing video AND audio associated? What am I doing wrong here?
I think you want something like this:
SELECT
Destaque.destaque, Noticia.id, Noticia.antetitulo,
Noticia.titulo, Noticia.lead, Noticia.legenda,
Noticia.publicacao, Seccao.descricao, Album.pasta,
Foto.ficheiro, Foto.descricao, Cronista.nome,
Cronista.profissao, Cronista.ficheiro,
AudioFile.*, AudioCollection.*, VideoFile.*, VideoCollection.*
FROM
nt_highlights AS Destaque
LEFT JOIN nt_noticias AS Noticia ON Destaque.noticia_id = Noticia.id
LEFT JOIN mm_fotos AS Foto ON Noticia.foto_id = Foto.id
LEFT JOIN nt_temas AS Seccao ON Noticia.tema_id = Seccao.id
LEFT JOIN mm_albuns AS Album ON Foto.album_id = Album.id
LEFT JOIN nt_cronistas AS Cronista ON Cronista.id = Noticia.cronista_id
LEFT JOIN ntNoticias_mmFiles AS AudioRel ON Rel.noticia_id = Noticia.id
AND AudioRel.file_id IN (
SELECT file_id
FROM ntNoticias_mmFiles
WHERE noticia_id = Noticia.id AND IsAudioFile = 1 /* whatever the check is */
LIMIT 1
)
LEFT JOIN mm_files AS AudioFile ON AudioFile.id = Rel.file_id
LEFT JOIN mm_coleccoes AS AudioCollection ON AudioFile.coleccao_id = AudioCollection.id
LEFT JOIN ntNoticias_mmFiles AS VideoRel ON VideoRel.noticia_id = Noticia.id
AND VideoRel.file_id IN (
SELECT file_id
FROM ntNoticias_mmFiles
WHERE noticia_id = Noticia.id AND IsVideoFile = 1 /* whatever the check is */
LIMIT 1
)
LEFT JOIN mm_files AS VideoFile ON VideoFile.id = Rel.file_id
AND VideoFile.IsVideoFile = 1
LEFT JOIN mm_coleccoes AS VideoCollection ON VideoFile.coleccao_id = VideoCollection.id
WHERE
Destaque.area_id = 1
AND Noticia.paraPublicacao = 1
AND Noticia.publicacao <= NOW()
ORDER BY
Destaque.destaque
My thought was this:
You want one audio file and one video file, at most. There are several files available per Noticia, so you need to make sure that a maximum of one file per type gets into the join. This also means you have to join in the ntNoticias_mmFiles table twice — once per type.
This is what the sub-queries in the join conditions are supposed to do: Select one row per file type. Going on from there you LEFT JOIN the rest of the data in, just like you already do.
The JOIN will return all the combinations, that's the problem.
If you only have one audio and/or videofile per article then you might want to look at subselects.
In SQL Server this would look something like (untested code):
SELECT title,
(select TOP 1 audio from audio where audio.aid = articles.id) as Audio,
(select TOP 1 video from video where video.aid = articles.id) as Video
FROM articles
Be careful that on large datasets this can perform poorly as the subselects in this example are executed individually for each row returned to the outer query. For example, if you return 10,000 articles then a total of 20,001 queries would actually be executed on the server.
There are other possible answers to overcome this but they get more involved (I suspect you could do something with a derived table but it eludes me at the moment).
You probably want to optimize that join query into a view. It's a large query, and with that many joins, it's going to be pretty inefficient. Plus, a view helps you debug the joins and will basically simplifies by allowing you to write your joins (in the view) and the WHERE clause (in your select from the view) separately, which can help with debugging the queries.