Hi my table structure is like this i am using laravel and postgres database
id | serving_start_time | serving_end_time
1 | 2016-10-05 00:24:08.894 | 2016-10-05 00:24:19.003
2 | 2016-10-05 00:24:59.875 | 2016-10-05 00:25:13.728
3 | 2016-10-05 11:43:52.055 | 2016-10-05 11:45:41.561
I want to calculate the 'total_serving_time'(serving_start_time-serving_end_time) and get only the min and max 'total_serving_time'. Is this possible in one query? please help
In one query like following?
SELECT
MIN(serving_end_time - serving_start_time) AS min_total_serving_time,
MAX(serving_end_time - serving_start_time) AS max_total_serving_time
FROM table;
Related
This question already has answers here:
PostgreSQL "Column does not exist" but it actually does
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SQL query column does not exist error
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As the title suggests, I have no clue why this doesn't work. If someone can point out what I am doing wrong it would be sweet.
Here's the current table rows and cols:
Makes table:
id | make
----+---------------
1 | Acura
Models Table:
id | model | makesId
-----+---------------------------------+---------
1 | CL | 1
2 | ILX | 1
3 | Integra | 1
4 | Legend | 1
5 | MDX | 1
6 | NSX | 1
7 | RDX | 1
8 | RL | 1
9 | RLX | 1
I am trying to query from both tables using a simple line with the WHERE clause with the following query:
SELECT models.model, makes.make
FROM models, makes
WHERE models.makesId = makes.id;
funprojectdb=# SELECT models.model, makes.make FROM models, makes WHERE models.makesId = makes.id;
ERROR: column models.makesid does not exist
LINE 1: ...models.model, makes.make FROM models, makes WHERE models.mak...
^
HINT: Perhaps you meant to reference the column "models.makesId".
The goal is to basically show me all of the models associated to the makes id.
Thanks to the people that answered my question.
It was an issue with postgres case sensitivity which I completely forgot about.
I will be re-doing the database columns with proper field names.
SQL newbie here. I'm trying to write a query that generates a scoring table, setting null to a student's grades in a module for which they haven't yet taken their exams (on PostgreSQL).
So I start with tables that look something like this:
student_evaluation:
|student_id| module_id | course_id |grade |
|----------|-----------|-----------|-------|
| 1 | 1 | 1 |3 |
| 1 | 1 | 1 |7 |
| 1 | 2 | 1 |8 |
| 2 | 4 | 2 |9 |
course_module:
| module_id | course_id |
| ---------- | --------- |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
In our use case, a course is made up of several modules. Each module has a single exam, but a student who failed his exam may have a couple of retries. The same module may also be present in different courses, but an exam attempt only counts for one instance of the module (ie. student A passed module 1's exam on course 1. If course 2 also has module 1, student A has to retake the same exam for course 2 if he also has access to that course).
So the output should look like this:
student_id
module_id
course_id
grade
1
1
1
3
1
1
1
7
1
2
1
8
1
3
1
null
2
4
2
9
I feel like this should have been a simple task, but I think I have a very flawed understanding of how outer and cross joins work. I have tried stuff like:
SELECT se.student_id, se.module_id, se.course_id, se.grade FROM student_evaluation se
RIGHT OUTER JOIN course_module ON course_module.course_id = se.course_id
AND course_module.module_id = se.module_id
or
SELECT se.student_id, se.module_id, se.course_id, se.grade FROM student_evaluation se
CROSS JOIN course_module WHERE course_module.course_id = se.course_id
Neither worked. These all feel wrong, but I'm lost as to what would be the proper way to go about this.
Thank you in advance.
I think you need both join types: first use a cross join to build a list of all combinations of students and courses, then use an outer join to add the grades.
SELECT sc.student_id,
sc.module_id,
sc.course_id,
se.grade
FROM student_evaluation se
RIGHT JOIN (SELECT s.student_id,
c.module_id,
c.course_id
FROM (SELECT DISTINCT student_id
FROM student_evaluation) AS s
CROSS JOIN course_module AS c) AS sc
USING (course_id));
I have this table inside my postgresql database,
item_code | date | price
==============================
aaaaaa.1 |2019/12/08 | 3.04
bbbbbb.b |2019/12/08 | 19.48
261893.c |2019/12/08 | 7.15
aaaaaa.1 |2019/12/17 | 4.15
bbbbbb.2 |2019/12/17 | 20
xxxxxx.5 |2019/03/12 | 3
xxxxxx.5 |2019/03/18 | 4.5
how can i calculate the average per item, per month over the year. so i get the result something like:
item_code | month | price
==============================
aaaaaa.1 | 2019/12 | 3.59
bbbbbb.2 | 2019/12 | 19.74
261893.c | 2019/12 | 7.15
xxxxxx.5 | 2019/03 | 3.75
I have tried to look and apply many alternatives but i am still not get the point, would really appreciate your help because i am new to postgresql.
I don't see how the question relates to a moving average. It seems you just want group by:
select item_code, date_trunc('month', date) as date_month, avg(price) as price
from mytable
group by item_code, date_month
This gives date_month as a date, truncated to the first day of the month - which I find more useful that the format you suggested. But it you do want that:
to_char(date, 'YYYY/MM') as date_month
I will be very grateful for your advice regarding the following issue.
Given:
PostgreSQL database
Initial (basic) query
select day, Value_1, Value_2, Value_3
from table
where day=current_date
which returns a row with following columns
Day | Value_1(int) | Value_2(int) | Value 3 (int)
2019-11-14 | 10 | 10 | 14
It is needed to create a view with this starting information and add a new row every day based on the outcome of initial query executed at 22:00.
The expected outcome tomorrow at 22:01 will be
Day | Value_1 | Value_2 | Value_3
2019-11-14 | 10 | 10 | 14
2019-11-15 | N | M | P
Many thanks in advance for your time and support.
After executing that query
select count(*) from tablename WHERE query=';';
that query will return count as 20.
But that table having totally 771498 records. while execute on SHOW STATUS LIKE 'sphinx_%';
it has return like this
+--------------------+--------+
| Variable_name | Value |
+--------------------+--------+
| sphinx_error | 5732 |
| sphinx_time | 837 |
| sphinx_total | 1000 |
| sphinx_total_found | 771498 |
| sphinx_word_count | 0 |
| sphinx_words | |
+--------------------+--------+
Here i have doubt .
what is sphinx_error?
what is sphinx_time?
what is sphinx_total?
what is sphinx_total_found?
what is sphinx_word_count?
what is sphinx_words?
It will be very helpful for me. Advance thanks
firstly sphinxse is not a real mysql table. Its a fake table. It accepts a query, then sphinxse forwards it to a running instance in the background, and returns the results to produce a 'table' to mysql.
So count(*) wont work. It simply runs the query and counts the rows. There are only 20 rows, unless you ask for more.
sphinx_error? - indicates an error - maybe SHOW WARNINGS would get the text.
sphinx_time? - how long in milisecons the query took
sphinx_total? - how many records you can actully retrieve (subject to max_matches)
sphinx_total_found? - how many records actully match
sphinx_word_count? - the number of words in your query
sphinx_words? - how many docs/hits match each of the words - because you have no query, its empty.