i have a table like this
i want to get the row of each table that have min responsetime
i have tried this query :
select tablename,
index1,
index2,
min(responsetime)
from tableconf
group by tablename
order by responsetime asc
but it doesn't give what i want
the output that i want is
+------------------+------------------+--------+--------------+
| tablename | index1 | index2 | responsetime |
+------------------+------------------+--------+--------------+
| salesorderheader | TotalDue | NULL | 6.1555 |
| salesterritory | Name | NULL | 11.66667 |
| store | BusinessEntityId | Name | 3.6222 |
| previous | previous | NULL | 5.03333 |
| NONE | NONE | NULL | 5.6 |
+------------------+------------------+--------+--------------+
what query i should use for get the output that i want
Select the minimum date per table name. Use an IN clause on these to get the rows:
select *
from tableconf
where (tablename, responsetime) in
(
select tablename, min(responsetime)
from tableconf
group by tablename
);
(Edited from previous answer)
I don't know if all SQL syntax accept a comma separated where parameter. Another option building off of the highest voted answer right now utilizes a join:
select *
from tableconf t
inner join (
select tablename, min(responsetime) min_rt
from tableconf t2
group by tablename
) t3 on t.tablename = t2.tablename and t.responsetime = t2.min_rt
Related
I don't know how to explain this in words. So please let me say an example.
Suppose the items table sorted by order column:
| id | name | order |
| 5 | x | 1 |
| 2 | y | 3 |
| 3 | z | 4 |
| 7 | p | 8 |
I want to update order column in a way which each of them has 1 difference with their successive row with keeping the order.
Desired result:
| id | name | order |
| 5 | x | 1 |
| 2 | y | 2 |
| 3 | z | 3 |
| 7 | p | 4 |
Edit:
Selecting row_number() isn't my solution as I want to change orders and I'm not just looking for the row number.
In MySQL8, just use row_number():
select t.*,
row_number() over(order by ord) as new_ord
from mytable t
This demonstrates that the information can easily be computed on the fly when needed and leads to the finding that storing such derived information might not be a good idea. It is tedious to keep it up to date when new rows are added or deleted.
Instead, you can use the above query, or put it in a view:
create view myview as
select t.*,
row_number() over(order by ord) as new_ord
from mytable t
Note: order is a language keyword, I used ord instead.
If you really need an update, for a one-time task for example:
update mytable t
inner join (
select id, row_number() over(order by ord) as new_ord from mytable
) t1 on t1.id = t.id
set t.ord = t1.new_ord
I would suggest using view for such requirement as also mentioned in other answer.
If this is the one time activity and if order is unique for each record then you can use the following query which uses corelated sub-query.
Update your_table t
Set t.order = (select count(1)
From your_table tt where tt.order <= t.order);
I have a MySQL DB and in it there's a table with activity logs of employees.
+-------------------------------------------------+
| log_id | employee_id | date_time | action_type |
+-------------------------------------------------+
| 1 | 1 | 2015/02/03 | action1 |
| 2 | 2 | 2015/02/01 | action1 |
| 3 | 2 | 2017/01/02 | action2 |
| 4 | 3 | 2016/02/12 | action1 |
| 5 | 1 | 2016/10/12 | action2 |
+-------------------------------------------------+
And I would need 2 queries. First, to get for every employee his last action. So from this example table I would need to get row 3,4 and 5 with all columns. And second, get the latest action only for specified employee.
Any ideas how to achieve this? I'm using Spring Data JPA, but raw SQL Query would be also great.
Thank you in advance.
Ready for a fred ed...
SELECT x.*
FROM my_table x
JOIN
( SELECT employee_id
, MAX(date_time) date_time
FROM my_table
GROUP
BY employee_id
) y
ON y.employee_id = x.employee_id
AND y.date_time = x.date_time;
For your first query. Simply
SELECT t1.*
FROM tableName t1
WHERE t1.log_id = (SELECT MAX(t2.log_id)
FROM tableName t2
WHERE t2.employee_id = t1.employee_id)
For the second one
SELECT t1.*
FROM tableName t1
WHERE t1.employee_id=X and t1.log_id = (SELECT MAX(t2.log_id)
FROM tableName t2
WHERE t2.employee_id = t1.employee_id);
You can get the expected output by doing a self join
select a.*
from demo a
left join demo b on a.employee_id = b.employee_id
and a.date_time < b.date_time
where b.employee_id is null
Note it may return multiple rows for single employee if there are rows with same date_time you might need a CASE statement and another attribute to decide which row should be picked to handle this kind of situation
Demo
I need a list of item names ordered by count of items. Item names and corresponing id's are stored in tabletwo while tableone refers to items by id's:
tableone tabletwo
+--------+-----------+ +----+------+
| itemid | condition | | id | name |
+--------+-----------+ +----+------+
| 2 | satisfied | | 1 | foo |
+--------+-----------+ +----+------+
| 1 | satisfied | | 2 | bar |
+--------+-----------+ +----+------+
| 3 | satisfied | | 3 | hurr |
+--------+-----------+ +----+------+
| 3 | satisfied | | 4 | durr |
+--------+-----------+ +----+------+
| 3 | satisfied |
+--------+-----------+
| 4 | satisfied |
+--------+-----------+
| 4 | satisfied |
+--------+-----------+
| 3 | nope |
+--------+-----------+
| 1 | satisfied |
+--------+-----------+
SQL code:
SELECT `itemname` FROM `tabletwo` WHERE `id` IN (
SELECT `itemid` FROM (
SELECT count(`itemid`), `itemid`
FROM `tableone`
WHERE `some_codition`="satisfied"
GROUP BY `itemid`
ORDER BY count(`itemid`) DESC
) alias
)
The nested SELECT returns a list of item id's in descendant order: 3, 4, 1, 2. This list is then used as an argument of an IN() clause. The expected result of the whole query is: hurr, durr, foo, bar (in this exact order). But the order is not preserved. I know it can be done like this: ORDER BY FIELD(id, 3, 4, 1, 2) but I don't know how to do this trick when the ordered list is fetched dynamically like in my case. Do I need to SELECT it again? Or temporary table maybe? Or is it better to build another query outside SQL?
Try using JOIN instead:
SELECT t2.`itemname`
FROM `tabletwo` AS t2
JOIN (
SELECT count(`itemid`) AS cnt, `itemid`
FROM `tableone`
WHERE `some_codition`="satisfied"
GROUP BY `itemid`
) AS t1 ON t1.`itemid` = t2.`id`
ORDER BY t1.cnt DESC
You can create a derived table using the subquery of the IN operator and perform a JOIN to this table, so that you are able to use the COUNT in the ORDER BY clause of the main query.
Use JOIN instead of IN:
SELECT
t2.name
FROM tabletwo t2
LEFT JOIN tableone t1
ON t1.itemid = t2.id
AND t1.`condition` = 'satisfied'
GROUP BY
t2.id, t2.name
ORDER BY COUNT(*) DESC
If you want to exclude rows from tabletwo that do not have a match on tableone, use INNER JOIN instead of LEFT JOIN.
ONLINE DEMO
I have a table like this:
+----+---------+------------+
| id | conn_id | read_date |
+----+---------+------------+
| 1 | 1 | 2010-02-21 |
| 2 | 1 | 2011-02-21 |
| 3 | 2 | 2011-02-21 |
| 4 | 2 | 2013-02-21 |
| 5 | 2 | 2014-02-21 |
+----+---------+------------+
I want the second highest read_date for particular 'conn_id's i.e. I want a group by on conn_id. Please help me figure this out.
Here's a solution for a particular conn_id :
select max (read_date) from my_table
where conn_id=1
and read_date<(
select max (read_date) from my_table
where conn_id=1
)
If you want to get it for all conn_id using group by, do this:
select t.conn_id, (select max(i.read_date) from my_table i
where i.conn_id=t.conn_id and i.read_date<max(t.read_date))
from my_table t group by conn_id;
Following answer should work in MSSQL :
select id,conn_id,read_date from (
select *,ROW_NUMBER() over(Partition by conn_id order by read_date desc) as RN
from my_table
)
where RN =2
There is an intresting article on use of rank functions in MySQL here : ROW_NUMBER() in MySQL
If your table design as ID - date matching (ie a big id always a big date), you can group by id, otherwise do the following:
$sql_max = '(select conn_id, max(read_date) max_date from tab group by 1) as tab_max';
$sql_max2 = "(select tab.conn_id,max(tab.read_date) max_date2 from tab, $sql_max
where tab.conn_id = tab_max.conn_id and tab.read_date < tab_max.max_date
group by 1) as tab_max2";
$sql = "select tab.* from tab, $sql_max2
where tab.conn_id = tab_max2.conn_id and tab.read_date = tab_max2.max_date2";
Firstly, pardon the incredibly vague/long question, I'm really not sure how to summarise my query without the full explanation.
Ok, I have a single MySQL table with the format like so
some_table
user_id
some_key
some_value
If you imagine that, for each user, there are multiple rows, for example:
1 | skill | html
1 | skill | php
1 | foo | bar
2 | skill | html
3 | skill | php
4 | foo | bar
If I want to find all the users who have listed HTML as a skill I can simply do:
SELECT user_id
FROM some_table
WHERE some_key = 'skill' AND some_value='html'
GROUP BY user_id
Easy enough. This would give me user ID's 1 and 2.
If I want to find all users who have listed HTML or PHP as a skill then I can do:
SELECT user_id
FROM some_table
WHERE (some_key = 'skill' AND some_value='html') OR (some_key = 'skill' AND some_value='php')
GROUP BY user_id
This would give me use ID's 1, 2 and 3.
Now, what I'm struggling to work out is how I can query the same table but this time say "give me all the users who have listed both HTML and PHP as a skill", i.e: just user ID 1.
Any advice, guidance or links to docs massively appreciated.
Thanks.
Here's one way:
SELECT user_id
FROM some_table
WHERE user_id IN (SELECT user_id FROM some_table where (some_key = 'skill' AND some_value='html'))
AND user_id IN (SELECT user_id FROM some_table where (some_key = 'skill' AND some_value='php'))
you need to use a nested query (or a self join, which is different)
I set up the following table.
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| type | char(10) | YES | | NULL | |
| value | char(10) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
inserted the following values
+------+-------+-------+
| id | type | value |
+------+-------+-------+
| 1 | skill | html |
| 1 | skill | php |
| 2 | skill | html |
| 3 | skill | php |
| 2 | skill | php |
+------+-------+-------+
ran this query
select id
from test
where type = 'skill'
and value = 'html'
and id in (
select id
from test
where type = 'skill'
and value = 'php');
and got
+------+
| id |
+------+
| 1 |
| 2 |
+------+
a self join would be as follows
select e1.id
from test e1, test e2
where e1.id = e2.id
and e2.type = 'skill'
and e2.value = 'html'
and e1.type = 'skill'
and e1.value = 'php'
;
and produce the same result.
so there you have two ways to try it in your code.
I don't know if this is valid for mysql, but should be (works for other db engines):
SELECT php.user_id
FROM some_table php, some_table html
WHERE php.user_id = html.user_id
AND php.some_key = 'skill'
AND html.some_key = 'skill'
AND php.some_value = 'php'
AND html.some_value = 'html';
And alternative, by using HAVING statement:
SELECT user_id, count(*)
FROM some_table
WHERE some_key = 'skill'
AND some_value in ('php','html')
GROUP BY user_id
HAVING count(*) = 2;
And a third option is to use inner selects. A slight alternative approach to David's approach:
SELECT user_id FROM some_table
WHERE
some_key = 'skill' AND
some_value = 'html' AND
user_id IN (
SELECT user_id FROM some_table
WHERE
some_key = 'skill' AND
some_value = 'php' AND
user_id IN (
SELECT user_id FROM some_table
WHERE
some_key = 'skill' AND
some_value = 'js' -- AND user_id IN ... for next level, etc.
)
);
... idea is that you can "pipe" the inner selects. With each new property you add new inner select to the most inner one.