So, lets say I have a table called "imports" that looks like this:
| id | importer_id | total_m | total_f |
|====|=============|=========|=========|
| 1 | 1 | 100 | 200 |
| 1 | 1 | 0 | 200 |
And I need the query to return it pivoted or transposed (rows to columns) in this way:
| total_m | sum(total_m) |
| total_f | sum(total_f) |
I can't think on a way to do this without using another table (maybe a temporary table?) and using unions, but there should be a better way to this anyway (maybe with CASE or IF?).
Thanks in advance.
select 'total_m', sum(total_m) from imports
union
select 'total_f', sum(total_f) from imports
http://sqlfiddle.com/#!9/fc1c0/2/0
You can "unpivot" by first expanding the number of rows, which is done below by cross joining a 2 row subquery. Then on each of those rows use relevant case expression conditions to align the former columns to the new rows ("conditional aggregates").
SQL Fiddle
MySQL 5.6 Schema Setup:
CREATE TABLE imports
(`id` int, `importer_id` int, `total_m` int, `total_f` int)
;
INSERT INTO imports
(`id`, `importer_id`, `total_m`, `total_f`)
VALUES
(1, 1, 100, 200),
(1, 1, 0, 200)
;
Query 1:
select
*
from (
select
i.importer_id
, concat('total_',cj.unpiv) total_type
, sum(case when cj.unpiv = 'm' then total_m
when cj.unpiv = 'f' then total_f else 0 end) as total
from imports i
cross join (select 'm' as unpiv union all select 'f') cj
group by
i.importer_id
, cj.unpiv
) d
Results:
| importer_id | total_type | total |
|-------------|------------|-------|
| 1 | total_f | 400 |
| 1 | total_m | 100 |
Related
Assessments table:
+---------------+-----------+---------------------+
| assessment_id | device_id | created_at |
+---------------+-----------+---------------------+
| 1 | 1 | 2022-07-15 20:03:03 |
| 2 | 2 | 2022-07-15 21:03:03 |
| 3 | 1 | 2022-07-15 22:03:03 |
| 4 | 2 | 2022-07-15 23:03:03 |
| 5 | 2 | 2022-07-15 23:03:03 |
+---------------+-----------+---------------------+
Results table:
+---------------+---------+--------+
| assessment_id | test | result |
+---------------+---------+--------+
| 1 | A | PASS |
| 2 | B | FAIL |
| 3 | A | FAIL |
| 4 | B | PASS |
| 5 | B | PASS |
+---------------+---------+--------+
Objective
I would like to return a row for each time the result of a test_id changes.
For example, Device 1 has Assessments 1 and 3. Test A in Assessment 1 was PASS, and Test A in Assessment 3 was FAIL, so we want to return this change as a row.
Device 2 has Assessments 2, 4, and 5. There was a test result change in Assessments 2 and 4 (Test B changed from FAIL to PASS), we want to return a row for this.
We do not want to return a row for Assessment 5 because Test B was PASS, and it was also PASS in Assessment 4. No change.
The resulting table would look like this:
+-----------+---------+------------------------+----------------+----------------------+--------------------+------------+----------------------+
| device_id | test_id | previous_assessment_id | previous_value | previous_value_date | next_assessment_id | next_value | next_value_date |
+-----------+---------+------------------------+----------------+----------------------+--------------------+------------+----------------------+
| 1 | A | 1 | PASS | 15/07/2022 20:03:03 | 3 | FAIL | 15/07/2022 22:03:03 |
| 2 | B | 2 | FAIL | 15/07/2022 21:03:03 | 4 | PASS | 15/07/2022 23:03:03 |
+-----------+---------+------------------------+----------------+----------------------+--------------------+------------+----------------------+
I've tried playing around with a couple of queries found here on SO, but they either took a long time and returned the wrong data, or didn't work at all. I don't think this is a duplicate because I'm using multiple tables, and every other question I've seen refers to a single table.
I've also looked at this SO question but could not get the helpful answer to apply to my situation.
I'm having some weird issue getting SQL Fiddle to work, but here is the test schema I've been tinkering with:
CREATE TABLE `assessments` (
`id` int,
`device_id` int,
`created_at` datetime
);
INSERT INTO `so_assessments` (`id`, `device_id`, `created_at`) VALUES (1, 1, '2022-07-09 22:56:00');
INSERT INTO `so_assessments` (`id`, `device_id`, `created_at`) VALUES (2, 2, '2022-07-10 22:56:06');
INSERT INTO `so_assessments` (`id`, `device_id`, `created_at`) VALUES (3, 1, '2022-07-11 22:56:11');
INSERT INTO `so_assessments` (`id`, `device_id`, `created_at`) VALUES (4, 2, '2022-07-12 22:56:17');
INSERT INTO `so_assessments` (`id`, `device_id`, `created_at`) VALUES (5, 2, '2022-07-13 22:56:24');
CREATE TABLE `results` (
`assessment_id` int,
`test` enum('A','B'),
`result` enum('PASS','FAIL')
);
INSERT INTO `results` (`assessment_id`, `test`, `result`) VALUES (1, 'A', 'PASS');
INSERT INTO `results` (`assessment_id`, `test`, `result`) VALUES (2, 'B', 'FAIL');
INSERT INTO `results` (`assessment_id`, `test`, `result`) VALUES (3, 'A', 'FAIL');
INSERT INTO `results` (`assessment_id`, `test`, `result`) VALUES (4, 'B', 'PASS');
INSERT INTO `results` (`assessment_id`, `test`, `result`) VALUES (5, 'B', 'PASS');
If you are using MySQL 8, Window functions can help. https://dev.mysql.com/doc/refman/8.0/en/window-function-descriptions.html
You can partition your results by device and test, and add a column that is the previous value of the result, then use the last row where the result differs from the previous value.
The following query creates a new column in your results with previous_value
SELECT
assessment_id,
device_id,
test,
result,
LAG (result) over w as `previous_value`,
LAG (assessment_id) over w as `previous_assessment_id`
FROM assessments join results using(assessment_id)
WINDOW w AS (PARTITION BY device_id, test ORDER BY assessment_id)
Yields the result:
+---------------+-----------+------+--------+----------------+------------------------+
| assessment_id | device_id | test | result | previous_value | previous_assessment_id |
+---------------+-----------+------+--------+----------------+------------------------+
| 1 | 1 | A | PASS | NULL | NULL |
| 3 | 1 | A | FAIL | PASS | 1 |
| 2 | 2 | B | FAIL | NULL | NULL |
| 4 | 2 | B | PASS | FAIL | 2 |
| 5 | 2 | B | PASS | PASS | 4 |
+---------------+-----------+------+--------+----------------+------------------------+
Which is a big part of the battle. Now we need to take that result and find the row for each device/test pair with the highest assessment_id, where result != previous_value.
The window is calculated after GROUP BY, ORDER BY, and even HAVING, so there's not much more that can be done in that query (that I have thought of) to narrow it down to the only the most recent entries for each device/test pair. So the above will have to be a subquery to get the final result.
Note: I am going to assume that if the result never changes, you want to show the first time that result was recorded. In other words, you want to count results with previous_value = NULL as a transition.
Here's a query that lists all the times the test result from a device/test pair changes:
SELECT * FROM
(SELECT
assessment_id,
device_id,
test,
result,
LAG (result) over w as `previous_value`
FROM assessments join results using(assessment_id)
WINDOW w AS (PARTITION BY `device_id`, `test` ORDER BY `assessment_id`)
) AS t
WHERE result != `previous_value` OR `previous_value` IS NULL
gets the result (I left out previous_assesssment_id and the others for space):
+---------------+-----------+------+--------+----------------+
| assessment_id | device_id | test | result | previous_value |
+---------------+-----------+------+--------+----------------+
| 1 | 1 | A | PASS | NULL |
| 3 | 1 | A | FAIL | PASS |
| 2 | 2 | B | FAIL | NULL |
| 4 | 2 | B | PASS | FAIL |
+---------------+-----------+------+--------+----------------+
EDIT
That's the answer to the question. If the first time the value is set is not of interest, just delete the OR part of the WHERE clause. There rest of this answer is because I convinced myself the problem was to get the MOST RECENT time the value flipped. I'm leaving it here, but only for interest.
Carrying On
This is all the times the outcome was different than previous, plus the first time a result was recorded. Almost there.
It would be tempting at this point to add another window in the outer query to aggregate the rows from above and identify the correct rows. But at least in MySQL 8, nested windows are not supported.
But given that result, we can create a query using MAX() and GROUP BY that gives the assessment_ids of all the rows we ultimately want:
SELECT MAX(assessment_id)
FROM (
SELECT
assessment_id,
device_id,
test,
result,
LAG (result) over w as `previous_value`,
LAG (assessment_id) over w as `previous_assessment_id`
FROM assessments join results using(assessment_id)
WINDOW w AS (PARTITION BY device_id, test ORDER BY assessment_id)
) AS t
where result != previous_value OR previous_value IS NULL
GROUP BY device_id, test
Which yields:
+--------------------+
| MAX(assessment_id) |
+--------------------+
| 3 |
| 4 |
+--------------------+
Now we know exactly which rows we need; but we built all that data about the previous values, and now we need a way to join the result of that query with the result of the subquery.
Happily, MySQL 8 has a way to stash a query and use it multiple times, called Common Table Expressions, that use the WITH clause docs here. So we can create the table with all the fun data, then use it as a subquery to get the id's we ultimately want, and then join that right back with the results we just created:
WITH
transitions AS (SELECT
assessment_id,
device_id,
test,
result,
LAG (result) over w as `previous_value`,
LAG (assessment_id) over w as `previous_assessment_id`
FROM assessments join results using(assessment_id)
WINDOW w AS (PARTITION BY device_id, test ORDER BY assessment_id)
)
SELECT transitions.*
FROM transitions
JOIN (
SELECT MAX(assessment_id) as assessment_id
FROM transitions
WHERE result != previous_value OR previous_value IS NULL
GROUP BY device_id, test
) AS t2 using (assessment_id)
Giving us the final answer (with the other columns you can fill in):
+---------------+-----------+------+--------+----------------+------------------------+
| assessment_id | device_id | test | result | previous_value | previous_assessment_id |
+---------------+-----------+------+--------+----------------+------------------------+
| 3 | 1 | A | FAIL | PASS | 1 |
| 4 | 2 | B | PASS | FAIL | 2 |
+---------------+-----------+------+--------+----------------+------------------------+
The first part creates a data set that includes all the information about what came before each test. Then we write a query that gets the id's of the interesting rows in that query, then we join back to the original data set to fill in all the columns.
You can use windows functions to peek at values of previous or successive rows according to an ordering and grouping.
For example:
select *
from (
select
a.device_id,
r.test,
a.id as prev_assessment_id,
r.result as prev_result,
a.created_at as prev_value_date,
lead(a.id) over(partition by a.device_id
order by a.created_at) as next_assessment_id,
lead(r.result) over(partition by a.device_id
order by a.created_at) as next_result,
lead(a.created_at) over(partition by a.device_id
order by a.created_at) as next_value_date
from assessments a
join results r on r.assessment_id = a.id
) x
where prev_result <> next_result
Result:
device_id test prev_assessment_id prev_result prev_value_date next_assessment_id next_result next_value_date
---------- ----- ------------------- ------------ -------------------- ------------------- ------------ -------------------
1 A 1 PASS 2022-07-09 22:56:00 3 FAIL 2022-07-11 22:56:11
2 B 2 FAIL 2022-07-10 22:56:06 4 PASS 2022-07-12 22:56:17
See running example at db<>fiddle.
Note: Your setup queries (that I used) include different data, compared to your expected result.
I'm pretty new to SQL and am currently trying to run a query which will return the total count of a value under a certain limit (using phpmyadmin).
Say we've got a table like so:
CarID | Car | OwnerID
-------------------
1 | Name | 1
2 | Name | 3
3 | Name | 2
4 | Name | 1
Now I would like to be able to get the total count of cars a owner has if it's under let's say 2 - to then get this:
OwnerID| TotalCars |
---------------------
2 | 1 |
3 | 1 |
How would I accomplish this? My situation is slightly different than the example I gave but it's fundamentally the same exact goal but just different numbers and more records.
When I try, those with more than the number I wish to see return with zero as their value??
(My code)
Code giving me trouble
(My result)
ID 6 has 3 properties so it shouldn't be showing me it at all and I don't understand why it's returning it as 0
You can use GROUP BY COUNT and HAVING
CREATE TABLE Table1
(`CarID` int, `Car` varchar(4), `OwnerID` int)
;
INSERT INTO Table1
(`CarID`, `Car`, `OwnerID`)
VALUES
(1, 'Name', 1),
(2, 'Name', 3),
(3, 'Name', 2),
(4, 'Name', 1)
;
SELECT `OwnerID`, COUNT(*) as countr
FROM Table1
GROUP BY `OwnerID`
HAVING countr < 2
OwnerID | countr
------: | -----:
3 | 1
2 | 1
db<>fiddle here
I want to match id's of column 1 from column 2.
_________________________________
| uid | profile_id | status |
|------|-------------|-----------
| 1 | 2 | checked |
| 2 | 1 | checked |
| 3 | 4 | unchecked|
| 4 | 1 | unchecked|
| 4 | 3 | checked |
| 1 | 4 | checked |
...
This is my table. I want to show the result of same values that match from id1 to id2 and status is checked. Following is the output:
__________________________
| uid | profile_id | status |
|------|-------------|-----------
| 1 | 2 | checked |
| 2 | 1 | checked |
...
Because id1 1 check the id2 2 and vice versa.
I done the following code.
SELECT
`aa`.`uid` AS `uid`,
`aa`.`profile_id` AS `profile_id`,
`aa`.`match_type` AS `match_type`
FROM
(
`matched_profiles` `aa`
left join `matched_profiles` `ab` on(
(`aa`.`uid` = `ab`.`profile_id`)
)
)
where
(
(`aa`.`uid` = `ab`.`profile_id`)
and (`ab`.`uid` = `aa`.`profile_id`)
);
but above code also show me the unchecked result.
Great question. Because of the structure of the data int this table, you can do this by joining the table to itself. You will have two sets of data, replicas of one another.
You want to make sure there is a two-way match between uid and profile_id.
You also want the status for both directions to be checked
SELECT
a.*
FROM matched_profiles a
inner join matched_profiles a2 on
a.uid = a2.profile_id
and a.profile_id = a2.uid
and a.status = 'checked'
and a2.status = 'checked';
You have a kind of explicit/inexplicit join going on. I reformatted to be completely explicit for clarity. You just need to add a filter to make sure all status values are checked.
Below is the SQL to build your test schema, which is nice to provide when asking these questions for SO users.
create table matched_profiles (
uid int,
profile_id int,
status varchar(18)
);
insert into matched_profiles
values
(1, 2, 'checked'),
(2, 1, 'checked'),
(3, 4, 'unchecked'),
(4, 1, 'unchecked'),
(4, 3, 'checked'),
(1, 4, 'checked');
This is a problem for which I have a working query, but it feels horribly inefficient to me and I'd like some help constructing a better one. This is going into a live production environment, and the number of queries the db handles each day is incredibly high, so the more efficient this can be, the better. I have a table structured something like this (stripped to just the relevant parts):
id | type | datecolumn
1 | A | 2014-01-01
1 | B | 0000-00-00
2 | A | 2014-01-02
2 | B | 2014-01-10
3 | A | 2014-01-01
3 | B | 0000-00-00
There will always be two rows for each id, one of type A and one of type B. A will always have a valid date, and B will either have a date >= that of A, or all 0s. What I want is a query that will produce output similar to this:
id | date for A | date for B
1 | 2014-01-01 | None
2 | 2014-01-02 | 2014-01-10
3 | 2014-01-01 | None
The way I'm doing this now is as follows:
SELECT
id,
IF(MIN(datecolumn) > 0, MIN(datecolumn), MAX(datecolumn)) AS 'date for A',
IF(MIN(datecolumn) > 0, MAX(datecolumn), 'None') AS 'date for B'
GROUP BY id
But it really feels like I should be able to pluck the datecolumn value on a by-type basis somehow. I know the simplest solution should be to change the table structure so that each id only uses one row, but I'm afraid that is not possible in this case; there has to be two rows. Is there a way to leverage the type column properly in this query?
Edit: Also, this is on a table that will have upwards of 10,000,000 rows. So again, efficiency is key.
I'd stick with what you've go, but maybe write it this way...
CREATE TABLE my_table
(id INT NOT NULL
,type CHAR(1) NOT NULL
,datecolumn DATE NOT NULL DEFAULT '0000-00-00'
,PRIMARY KEY(id,type)
);
INSERT INTO my_table VALUES
(1 ,'A','2014-01-01'),
(1 ,'B','0000-00-00'),
(2 ,'A','2014-01-02'),
(2 ,'B','2014-01-10'),
(3 ,'A','2014-01-01'),
(3 ,'B','0000-00-00');
SELECT id
, MAX(CASE WHEN type = 'A' THEN datecolumn END) a
, MAX(REPLACE(CASE WHEN type='B' THEN datecolumn END,'0000-00-00','none')) b
FROM my_table
GROUP
BY id;
+----+------------+------------+
| id | a | b |
+----+------------+------------+
| 1 | 2014-01-01 | none |
| 2 | 2014-01-02 | 2014-01-10 |
| 3 | 2014-01-01 | none |
+----+------------+------------+
Make sure you have an index that covers both the id and type columns (e.g ALTER TABLE tbl ADD INDEX (type,id)), then do:
SELECT
table_a.id,
table_a.datecolumn AS 'date for A',
IF(table_b.datecolumn > 0, table_b.datecolumn, 'None') AS 'date for B'
FROM tbl AS table_a
JOIN tbl AS table_b ON table_a.id = table_b.id AND table_b.type = 'B'
WHERE table_a.type = 'A';
Let's say I have such a table (ordered by date):
id | name | type | date
1 | A | 1 | 01-08-2012
2 | A | 2 | 01-08-2012
3 | B | 1 | 02-09-2012
4 | A | 1 | 01-10-2012
5 | A | 4 | 01-10-2012
6 | A | 5 | 02-10-2012
I want to group subsequent rows that have the same 'name' value and count them:
name | count
A | 2
B | 1
A | 3
I was thinking about writing a stored procedure and using cursors, but I was also wondering, if there's a simpler solution, for example using nested SELECTs, etc.
My question is very similar to: how to group array and count them, but that one concerns PHP.
To do that I used a couple of variables,
the table structure, I created my own just for testing and it's:
create table abc (id int, name varchar(20),type int);
insert into abc values
( 1 , 'A' , 1 ),
( 2 , 'A' , 2 ),
( 3 , 'B' , 1 ),
( 4 , 'A' , 1 ),
( 5 , 'A' , 4 ),
( 6 , 'A' , 5 )
the query ended being like this:
set #a:='';
set #counter:=1;
set #groupby:=0;
select *,count(REPEATED) from (select name,if(#a=name,#counter:=#counter+1,#counter:=1) as rep,if(#counter=1,#groupby:=#groupby+1,#groupby) as repeated,#a:=name type from abc) as t group by repeated
you can see it works in SQLFIDDLE if you have any question let me know.
In the SQLFIDDLE