Ok, I have a single MySQL table with the name 'car' and 3 columns.
+----+--------+------------+
| ID | car_id | engine |
+----+--------+------------+
| 1 | 123 | on |
| 2 | 123 | on |
| 3 | 123 | off |
| 4 | 123 | on |
| 5 | 123 | on |
| 6 | 123 | on |
| 7 | 123 | off |
| 8 | 123 | on |
| 9 | 123 | off |
+----+--------+------------+
Now I want to show the trips this car did. The trips would be determined based on car engine start and stop. For example from the above example we can see that user has made 3 trips as total(From on to off). Now What I want is that if there is a query which gives me only 3 results from on to off meaning if somehow the query groups the records by considering a starting point on and ending point off. Is it possible in mysql? or the other way around is doing it manually by fetching all the records and working in arrays?
At the moment I am fetching all the records and doing it manually by looping all the data and doing accordingly But this process is slow.
Can you try it ?
SELECT * from cars WHERE `engine` = 'off' AND id IN(SELECT id+1 FROM `cars` WHERE `engine` = 'on')
Related
A table contains the following data, is using INNODB, has a UNIQUE constraint on position/fk, and doesn't allow NULL for position.
+----+----------+-----+
| id | position | fk |
+----+----------+-----+
| 1 | 1 | 123 |
| 2 | 2 | 123 |
| 3 | 3 | 123 |
| 4 | 4 | 123 |
| 5 | 5 | 123 |
| 6 | 6 | 123 |
| 7 | 7 | 123 |
| 8 | 8 | 123 |
| 9 | 9 | 123 |
| 10 | 10 | 123 |
+----+----------+-----+
PHP receives a request to update the table to the following. The format of the request can be provided how ever is most convenient such as [2,1,4,3,6,5,8,7,10,9] or [{"id":1, "position":2}, ... ], etc.
+----+----------+-----+
| id | position | fk |
+----+----------+-----+
| 1 | 2 | 123 |
| 2 | 1 | 123 |
| 3 | 4 | 123 |
| 4 | 3 | 123 |
| 5 | 6 | 123 |
| 6 | 5 | 123 |
| 7 | 8 | 123 |
| 8 | 7 | 123 |
| 9 | 10 | 123 |
| 10 | 9 | 123 |
+----+----------+-----+
I've confirmed that SET unique_checks=0; will not allow unique checks to be temporarily disabled, and don't wish to actually remove the unique index, update the table, and reapply the unique index.
How can this table be updated?
If there is no simple means to do so, I thought of a couple of options, but don't like them:
Allowing NULL in position. Is there a way to temporarily allow NULL similar to how SET FOREIGN_KEY_CHECKS=0; can disable foreign keys?
First delete all the records and then reinsert them. This might result in performance issues as there are indexes on the table which will need to be recreated.
All I can think is that you need to first change all the positions to some other values that aren't in the range of new position values you ultimately need to set, but are still unique within the rows.
An easy way to do this, assuming your position column is a signed integer, is to set all the positions to their opposite (negative) value. They'll remain unique, but they won't be in the set of the new values.
You can do this in a transaction along with your subsequent updates, so no other concurrent transaction will ever see the negative values.
BEGIN;
UPDATE MyTable SET position = -position;
UPDATE MyTable SET position = 2 WHERE id = 1;
...etc...
COMMIT;
This is a hack. The sign bit of the integer is being used for a purpose other than showing negative numbers.
i am trying to build something like an order management tool for a car garage.
The main function of the tool is to manage repair orders and inspection orders as well
Therefore i have created this following three tables.
In the first one you can see the cars and the state of the repair and inspection.
The second one shows the information about the single repair orders the relation between the first and this is 1:n.
The last one shows the automaticly created inspection orders for each car out of the first table. This is an 1:n relation as well.
So what i try to do is to show all the open repair and inspection orders for the cars in one table. But only the open ones.
I tried it with some where statements but i got totaly confused.
My question is, how i can realise it?
+------+--------------------------+----------+------------+
| IDWZ | wz_name | wz_stand | wz_vistand |
+------+--------------------------+----------+------------+
| 1 | Querbr?cke vorn | 0 | 0 |
| 2 | Front Lateral Support | 0 | 1 |
| 3 | Rear Support | 1 | 1 |
| 4 | MID-X-Member Upper Shell | 1 | 1 |
| 5 | Front Lateral Support | 1 | 1 |
+------+--------------------------+----------+------------+
+---------+-----------------+--------------+
| IDWZTBL | rep_wzrepstatus | rep_wzfehler |
+---------+-----------------+--------------+
| 2 | 1 | REP 1 |
| 1 | 1 | REp2 |
| 1 | 1 | REp 3 MASS |
| 1 | 0 | 444 |
| 2 | 0 | |
+---------+-----------------+--------------+
+--------+-------------+
| VIWZID | vi_repstand |
+--------+-------------+
| 1 | 0 |
+--------+-------------+
Sry for that!
So the IDWZ is the foreign KEY in the second table(IDWZTBL) and in the third (VIWZID).
I tried it with
SELECT wz_name, wz_stand, wz_vistand, rep_wzrepstatus, vi_repstand FROM tbl_wz LEFT JOIN tbl_orders ON tbl_wz.IDWZ = tbl_orders.IDWZTBL LEFT JOIN tbl_vi ON tbl_wz.IDWZ = tbl_vi.VIWZID WHERE wz_stand='0' AND rep_wzrepstatus='0' ...
Only for the first table cars to the second one repair orders, that WHERE staement (WHERE wz_stand='0' AND rep_wzrepstatus='0') works fine.
But if i try to add the third table (VI) doing the same, i could fetch the result i wanna have.
What i wanna see in the Overview table is only the last open repair order and the last open inspection order.
i'm new to MySQL and PHP. And i have some problems trying to get data values from two tables in one query using JOIN. What i want to do is query "user_builds" and SUM(amount) where the owner_id=1 AND type=1. The problems comes in now where i have to grab the build_type from another table called "builds".
I have tried to solve this as i mentioned with JOIN, but the closest i came was to get the amount of rows that was equal to how many rows user_id=1 had.
What i want is select the total SUM of "amount"(user_builds) where "type=1"(builds) and "owner_id=1"(user_builds).
I hope you understand what i try to do here, if not i will try to elaborate it more. And also sorry for not providing any of the querys i tried, but as none of them worked it feels irrelevant. Thank you for your time.
Edit:
+-------------------+
| user_builds |
+---------+---------+----------+-------+
| id |owner_id | build_id | amount|
+---------+---------+----------+-------+
| 1 | 1 | 1 | 5 |
| 2 | 2 | 2 | 15 |
| 3 | 2 | 3 | 15 |
| 4 | 1 | 4 | 5 |
| 5 | 1 | 5 | 5 |
| 6 | 1 | 6 | 10 |
+---------+---------+----------+-------+
+----------------------+
| build |
+---------+------------+-----------+--------+
| id | name |description| type |
+---------+------------+-----------+--------+
| 1 | House | desc | 1 |
| 2 | Kitchen | desc | 2 |
+---------+------------+-----------+--------+
I want to query "user_builds" and get the total of "amount" where owner_id=1 and type=1. (type is found in "build" table).
Try this code, I hope it works appropriately.
select sum(ub.amount)
from user_builds ub
left join build b
on ub.build_id = b.id
where b.type=1
and ub.owner_id = 1
select SUM(amount) from user_builds left join builds on build.type = user_builds.type where "owner_id=1"
try this query and replace my query field with your original fields
best of luck...
Okay so I'm creating a task manager for my company. A user can assign assign a task to multiple other users. So I've though of 2 ways of implementing this.
This is my tasks table for option one (at least the columns that are important in this discussion ):
----------------------------------------------
| id | assigned_to | assigned_from |
---------------------------------------------
| 1 | 1,3,6 | 4 |
--------------------------------------------
| 2 | 1,4 | 2 |
---------------------------------------------
So here I pretty much just comma separate each user_id that is assigned to this particular task
Option 2:
----------------------------------------------------------
| id | task_id | assigned_to | assigned_from |
------------------------------------------------------------
| 1 | 335901 | 1 | 4 |
-----------------------------------------------------------
| 2 | 335901 | 3 | 4 |
-----------------------------------------------------------
| 3 | 335901 | 6 | 4 |
-----------------------------------------------------------
| 4 | 564520 | 1 | 2 |
-----------------------------------------------------------
| 4 | 564520 | 4 | 2 |
-----------------------------------------------------------
So as you can see here instead of putting the assiged_to is's here I just create a task id which is a random number and then I can groupBy 'task_id'. This is currently they way I have built it but for some reason it feels like it might screw me over in the future (not that option one doesn't give me the same feeling). So my question is which way do you guys recommend or is there maybe a different better way that I could be doing this?
Option 2 ist the better solution since you can acutally work with the table. You may e.g. create another table Tasks with
Task_id | Task_name | Budget | ...
Or a table with user-IDs for assigned_to and assigned_from. All these tables can be joined together if you use 2nd Option.
btw it is the correct normalization form
You can use Option 2 and normalize further if tasks are always assigned by/from the same person.
Tasks table:
task_id | assigned_from
1 | 4
2 | 2
The Assignees table then doesn't need to have the assigned_from since it's always the same for that task_id:
id | task_id | assigned_to
1 | 1 | 1
2 | 1 | 3
3 | 1 | 6
4 | 2 | 1
5 | 2 | 4
i have a table in following format:
id | title
---+----------------------------
1 | php jobs, usa
3 | usa, php, jobs
4 | ca, mysql developer
5 | developer
i want to get the most popular keywords in title field, please guide.
If you have a list of keywords, you can do the following:
select kw.keyword, count(*)
from t cross join
keywords kw
on concat(', ', t.title, ',') like concat(', ', kw.keyword, ',')
As others have mentioned, though, you have a non-relational database design. The keywords in the title should be stored in separate rows, rather than as a comma separated list.
If your data is small (a few hundred thousand rows or less), you can put it into Excel, use the text-to-columns function, rearrange the keywords, and create a new, better table in the database.
SELECT title 1, COUNT(*) FROM table GROUP BY title 1
EDIT
Since you've edited and presented a non-normalized table, I would recommend you normalize it.
Have a read of: http://blog.fedecarg.com/2009/02/22/mysql-split-string-function/
You need to modify your database. You should have something like this:
items
+----+---------------+
| id | title |
+----+---------------+
| 1 | something |
| 3 | another thing |
| 4 | yet another |
| 5 | one last one |
+----+---------------+
keywords
+----+-----------------+
| id | keyword |
+----+-----------------+
| 1 | php jobs |
| 2 | usa |
| 3 | php |
| 4 | jobs |
| 5 | ca |
| 6 | mysql developer |
| 7 | developer |
+----+-----------------+
items_to_keywords
+---------+------------+
| item_id | keyword_id |
+---------+------------+
| 1 | 1 |
| 1 | 2 |
| 3 | 2 |
| 3 | 3 |
| 3 | 4 |
| 4 | 5 |
| 4 | 6 |
| 5 | 7 |
+---------+------------+
Do you see the advantage? The ability to make relations is what you should be leveraging here.