I'm using 3 tables to collect data from. The proces looks like:
User write VIN to form
Script search in table 1 for case_id and country base on that vin
number
After that he use case_id and country for search in table number 2
and get calculation id from there
Base on that calculation id and case id it search in 3th table
.
My script looks like this:
SELECT
cases.case_id,
cases.lastcalc_model_options,
cases.country,
calculations.calculation_id,
calculations.license,
positions.text
FROM cases
INNER JOIN calculations ON(cases.case_id =calculations.case_id
AND cases.country = calculations.country)
INNER JOIN positions ON(calculations.case_id = positions.case_id
AND calculations.calculation_id = positions.calculation_id)
WHERE vin ='ABCDEFGH'
This select work correctly, problem start when for example there is for example no result in table positions with that case_id and calculation_id. Instead of give back atleast everything it found in other tables it return NOTHING.
Is there a way to change this kind of komplex SELECT to return everything it found not return something only when every condition is TRUE?
Your problem is the INNER JOIN. Using INNER JOIN your result only contains entries present in all tables. Try using LEFT JOIN instead.
SELECT
cases.case_id,
cases.lastcalc_model_options,
cases.country,
calculations.calculation_id,
calculations.license,
positions.text
FROM cases
LEFT JOIN calculations ON(cases.case_id =calculations.case_id
AND cases.country = calculations.country)
LEFT JOIN positions ON(calculations.case_id = positions.case_id
AND calculations.calculation_id = positions.calculation_id)
WHERE vin ='ABCDEFGH'
See this stackoverlow answer for some more indepth information.
INNER JOIN returns rows from both tables only if there is a match between the columns in both tables.
You may try LEFT JOIN or FULL OUTER JOIN instead.
Related
I wrote a query to update the imageSrc of an object on database : UPDATE BOXES SET BOXES.IMAGESRC = ?1 WHERE BOXES.ID = ?2 , and it actually works, because I checked on the database my table Boxes and it updated correctly the imageSrc of the Box with ID=1.
(Result here)
My problem comes when I execute the following LEFT JOIN query SELECT * FROM BOXES AS A LEFT JOIN MATCHES_BOXES AS B ON A.ID=B.MATCH_ID WHERE B.MATCH_ID LIKE ?1 Because it gives me the Box with ID=1 with is OLD imageSrc (Result of LEFT JOIN)
As you can see, the BOX with ID=1 does not cointains the correct imageSrc (/resources/images/cards/blue-01.png), instead, it cointains the old imageSrc (/resources/images/celda.png)
And it does not make sense to me, because I LEFT JOINED with the table Boxes, where the Box with ID=1 already have the correct imageSrc, but returns the old.
This happens as your where clause on the left join converts the query into an inner join.
SELECT *
FROM BOXES AS A
LEFT JOIN MATCHES_BOXES AS B
ON A.ID=B.MATCH_ID
WHERE B.MATCH_ID LIKE ?1
Analyze the scenarion, if you wanted to get recrods in Boxes regardless of whether it was present in MATCHES_BOXES then the resulting rows from B will all have been NULL for the missing MATCH_ID in B(ie no_row_exists).
But since you got a WHERE B.MATCH_ID LIKE '?1' condition after the JOIN, it will negate those missing MATCH_ID as you are basically check WHERE NULL like '?1' and since NULL cannot get equated with anything, the missing recrods are not retreived in the query.
If your intention is to get all records from BOXES even if they dont exist in MATCHES_BOXES, and also those records from BOXES which exist in MATCHES_BOXES on the ID and you wish to bring them only if MATCH_ID LIKE '?1', the you would JOIN on the AND condition as follows
SELECT *
FROM BOXES AS A
LEFT JOIN MATCHES_BOXES AS B
ON A.ID=B.MATCH_ID
AND B.MATCH_ID LIKE ?1 /*use AND instead of WHERE*/
The outer join doesn't seem to make much sense. Anyway, you are selecting MATCHES_BOXES looking for a particular MATCH_ID (3 in your sample result). You join the BOXES table on the same column. Thus you are showing BOXES with the ID 3. MATCHES_BOXES also has a column BOXES_ID. This has nothing to do with the joined BOXES row, however. When you see the IMAGESRC for BOXES row for ID 3, it is because you are joining this row.
I suppose you simply want to join on BOXES_ID instead:
SELECT *
FROM boxes b
JOIN matches_boxes mb ON mb.boxes_id = b.id
WHERE mb.match_id = ?1;
SELECT team_with.participant1,team_with.participant2,team_with.participant3
FROM event,team_with
WHERE team_with.for_event_no=event.event_no AND
event.event_no=4 AND
team_with.participant1=9 OR
team_with.participant2=9 OR
team_with.participant3=9;
I have written the particular query, and obtained the required id's in a row. I am not able to modify this query such that, in place of these id's, names connected to the id's are displayed.
The student_detatil table consists of PK(sam_id) and the attribute name.
IDs displayed by the present query are FKs connected to student_detail.sam_id..
It seems like a bad design to multiply columns storing different participants. Consider creating a separate row for each participant and storing them in a table. Your joining logic would also be easier.
Also, please use explicit JOIN syntax - it makes the query clearer and easier to understand by separating join logic with conditions for data retrieval.
Remember that operator AND has a precedence over OR, so that your event.event_no = 4 does not apply to each participant condition. I believe this was a mistake, but you are the one to judge.
As to the query itself, you could apply OR conditions into join, or simply join the student_detail table thrice.
SELECT
s1.name,
s2.name,
s3.name
FROM
event e
INNER JOIN team_with t ON t.for_event_no = e.event_no
LEFT JOIN student_detail s1 ON s1.sam_id = t.participant1
LEFT JOIN student_detail s2 ON s2.sam_id = t.participant2
LEFT JOIN student_detail s3 ON s3.sam_id = t.participant3
WHERE
e.event_no = 4
AND ( t.participant1=9 OR t.participant2=9 OR t.participant3=9 );
SELECT submissions.created_at, guests.accepted
FROM submission
INNER JOIN guests
ON guests.event_id = 1
ORDER BY submissions.created_at ASC;
Currently this query is taking a long time to run (may not even return everything).
What I am trying to accomplish:
Grab the field submissions.created at and guests.accepted (the two are linked by a submission_id)
given a certain event_id (event 1 for example).
What is wrong with my query?
You forgot to give the JOIN condition in your query. Try this:
SELECT submissions.created_at, guests.accepted
FROM submission s
INNER JOIN guests g on g.event_id = s.submissions_id
where guests.event_id = 1
ORDER BY submissions.created_at ASC;
SELECT submissions.created_at, guests.accepted
FROM submission
INNER JOIN guests
ON guests.(column to match against) = submissions.(column to match on)
where guests.event_id=1
ORDER BY submissions.created_at ASC;
As many others here have already said, your join is a little goofed. It's attempting to join the one row that matches in the guests table against every single row in the submission column.
You would need to do your join like this :
Inner join guest on guest.event_id = submissions_id
where guest.event_id = 1
When you join you need to join on two columns from different table (most of the time id columns)
You can read the MySQL example for more explanation. And here is the link to the MySQL reference manual
In my SQL query i'm checking on different parameters. Nothing strange happens when there is data in each of the tables for the inserted tripcode. But when one table has no data in it I don't get any data at all. Even if the other tables have data. So I need to be able to check if the table has data in it and if it has, I need to select.
SELECT roadtrip_tblgeneral.*,
GROUP_CONCAT(distinct roadtrip_tblhotels.hotel) as hotels,
GROUP_CONCAT(distinct roadtrip_tbllocations.location) as locations,
GROUP_CONCAT(distinct roadtrip_tbltransports.transport) as transports
FROM roadtrip_tblgeneral
INNER JOIN roadtrip_tblhotels
ON roadtrip_tblgeneral.id = roadtrip_tblhotels.tripid
INNER JOIN roadtrip_tbllocations
ON roadtrip_tblgeneral.id = roadtrip_tbllocations.tripid
INNER JOIN roadtrip_tbltransports
ON roadtrip_tblgeneral.id = roadtrip_tbltransports.tripid
WHERE roadtrip_tblgeneral.tripcode = :tripcode
GROUP BY roadtrip_tblgeneral.id
Only the tables with the GROUP_CONCAT in front need the check. I already tried with the keyword EXISTS in front of it.
Thanks in advance.
The INNER JOIN keyword returns rows when there is at least one match in both tables. You can't have a match if there is no data, perhaps you want to use a LEFT JOIN or a FULL JOIN.
Left join will be use as it returns all the data from the table at left, even if there is no matching rows in right table
I have two tables: projects and user_licenses.
I'd like to grab the entire list of projects from the database, as well as the user's current license state. The licenses table has a user ID field which I check against a $_SESSION variable for the value. The thing is, they might not have a license, or a non-logged in visitor may want to see the projects list. My question is this: How can I get the data from the left table always display, but only grab data for that row from the right table when certain conditions are met?
The query I have at the moment is this:
SELECT Projects.*,
UserLicenses.*
FROM Projects
LEFT JOIN UserLicenses ON Projects.id = UserLicenses.project_id
WHERE UserLicenses.user_id = 12
ORDER BY name ASC
Add any extra conditions to the on clause of the left join. They will only affect the joined table.
SELECT Projects.*,
UserLicenses.*
FROM Projects
LEFT JOIN UserLicenses
ON Projects.id = UserLicenses.project_id
and UserLicenses.user_id = 12
and UserLicences.Question = '6*7'
and UserLicences.Answer = 42
ORDER BY name ASC
This will return projects without matching licenses.
Move the UserLicenses condition away from WHERE, and up to the JOIN condition. By having it in the WHERE part, you will never see those "left" rows because they are filtered away.
You can also probably use WHERE (UserLicenses.user_id = 12 OR UserLicenses.user_id IS NULL)
Don't do that. Just move it to the join condition like this:
LEFT JOIN UserLicenses ON
(Projects.id = UserLicenses.project_id AND UserLicenses.user_id = 12)
You can use LEFT JOIN
If its conditions match then values show otherwise null value shows.