I'm trying to insert different numbers of rows into my table by adjusting #s:=1 and #s<1000 but it only inserts one at a time. What am I doing wrong?
INSERT INTO
rent
(
id
)
select #s:=#s+1 as seq
FROM (SELECT #s:=1) AS baseview, rent
WHERE #s<1000
ORDER by #s ASC;
Can you try this?:
INSERT INTO
rent
(
id
)
SELECT seq FROM (
select #s:=#s+1 as seq
FROM (SELECT #s:=1) AS baseview, rent
WHERE #s<1000
ORDER by #s ASC
) seqSource;
Related
I'm trying in MySql to count the number of users created each day and then get an accumulative figure on a row by row basis. I have followed other suggestions on here, but I cannot seem to get the accumulation to be correct.
The problem is that it keeps counting from the base number of 200 and not taking account of previous rows.
Where was I would expect it to return
My Sql is as follows;
SELECT day(created_at), count(*), (#something := #something+count(*)) as value
FROM myTable
CROSS JOIN (SELECT #something := 200) r
GROUP BY day(created_at);
To create the table and populate it you can use;
CREATE TABLE myTable (
id INT AUTO_INCREMENT,
created_at DATETIME,
PRIMARY KEY (id)
);
INSERT INTO myTable (created_at)
VALUES ('2018-04-01'),
('2018-04-01'),
('2018-04-01'),
('2018-04-01'),
('2018-04-02'),
('2018-04-02'),
('2018-04-02'),
('2018-04-03'),
('2018-04-03');
You can view this on SqlFiddle.
Use a subquery:
SELECT day, cnt, (#s := #s + cnt)
FROM (SELECT day(created_at) as day, count(*) as cnt
FROM myTable
GROUP BY day(created_at)
) d CROSS JOIN
(SELECT #s := 0) r;
GROUP BY and variables have not worked together for a long time. In more recent versions, ORDER BY also needs a subquery.
here i am trying to insert patient_id and nurse_id which are from two different tables.
insert into nurse_take_care(patient_id,nurse_id) values (patient_id(select MAX(p_id) from patient;), nurse_id(Select n_id from nurse order by Rand() limit 1;))
is this the right way to do??
The query would be like:
insert into nurse_take_care(patient_id,nurse_id) values
(select MAX(p_id) from patient limit 1, Select n_id from nurse order by Rand() limit 1);
Please try this insert into nurse_take_care(patient_id,nurse_id)
SELECT (select MAX(p_id) from patient) as p_id, (select n_id from nurse order by Rand() limit 1) as n_id
Try something like this:
INSERT INTO nurse_take_care (patient_id, nurse_id)
SELECT ( SELECT MAX(p_id) FROM patient ),
( SELECT n_id FROM nurse ORDER BY RAND() LIMIT 1 )
Let's say I was looking for the second most highest record.
Sample Table:
CREATE TABLE `my_table` (
`id` int(2) NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
`value` int(10),
PRIMARY KEY (`id`)
);
INSERT INTO `my_table` (`id`, `name`, `value`) VALUES (NULL, 'foo', '200'), (NULL, 'bar', '100'), (NULL, 'baz', '0'), (NULL, 'quux', '300');
The second highest value is foo. How many ways can you get this result?
The obvious example is:
SELECT name FROM my_table ORDER BY value DESC LIMIT 1 OFFSET 1;
Can you think of other examples?
I was trying this one, but LIMIT & IN/ALL/ANY/SOME subquery is not supported.
SELECT name FROM my_table WHERE value IN (
SELECT MIN(value) FROM my_table ORDER BY value DESC LIMIT 1
) LIMIT 1;
Eduardo's solution in standard SQL
select *
from (
select id,
name,
value,
row_number() over (order by value) as rn
from my_table t
) t
where rn = 1 -- can pick any row using this
This works on any modern DBMS except MySQL. This solution is usually faster than solutions using sub-selects. It also can easily return the 2nd, 3rd, ... row (again this is achievable with Eduardo's solution as well).
It can also be adjusted to count by groups (adding a partition by) so the "greatest-n-per-group" problem can be solved with the same pattern.
Here is a SQLFiddle to play around with: http://sqlfiddle.com/#!12/286d0/1
This only works for exactly the second highest:
SELECT * FROM my_table two
WHERE EXISTS (
SELECT * FROM my_table one
WHERE one.value > two.value
AND NOT EXISTS (
SELECT * FROM my_table zero
WHERE zero.value > one.value
)
)
LIMIT 1
;
This one emulates a window function rank() for platforms that don't have them. It can also be adapted for ranks <> 2 by altering one constant:
SELECT one.*
-- , 1+COALESCE(agg.rnk,0) AS rnk
FROM my_table one
LEFT JOIN (
SELECT one.id , COUNT(*) AS rnk
FROM my_table one
JOIN my_table cnt ON cnt.value > one.value
GROUP BY one.id
) agg ON agg.id = one.id
WHERE agg.rnk=1 -- the aggregate starts counting at zero
;
Both solutions need functional self-joins (I don't know if mysql allows them, IIRC it only disallows them if the table is the target for updates or deletes)
The below one does not need window functions, but uses a recursive query to enumerate the rankings:
WITH RECURSIVE agg AS (
SELECT one.id
, one.value
, 1 AS rnk
FROM my_table one
WHERE NOT EXISTS (
SELECT * FROM my_table zero
WHERE zero.value > one.value
)
UNION ALL
SELECT two.id
, two.value
, agg.rnk+1 AS rnk
FROM my_table two
JOIN agg ON two.value < agg.value
WHERE NOT EXISTS (
SELECT * FROM my_table nx
WHERE nx.value > two.value
AND nx.value < agg.value
)
)
SELECT * FROM agg
WHERE rnk = 2
;
(the recursive query will not work in mysql, obviously)
You can use inline initialization like this:
select * from (
select id,
name,
value,
#curRank := #curRank + 1 AS rank
from my_table t, (SELECT #curRank := 0) r
order by value desc
) tb
where tb.rank = 2
SELECT name
FROM my_table
WHERE value < (SELECT max(value) FROM my_table)
ORDER BY value DESC
LIMIT 1
SELECT name
FROM my_table
WHERE value = (
SELECT min(r.value)
FROM (
SELECT name, value
FROM my_table
ORDER BY value DESC
LIMIT 2
) r
)
LIMIT 1
I have a table like this:
Fiddle: http://sqlfiddle.com/#!2/44d9e/14
CREATE TABLE IF NOT EXISTS `mytable` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(20) NOT NULL,
`money_earned` int(20) NOT NULL,
PRIMARY KEY (`id`)
) ;
INSERT INTO mytable (user_id,money_earned) VALUES ("111","10");
INSERT INTO mytable (user_id,money_earned) VALUES ("111","6");
INSERT INTO mytable (user_id,money_earned) VALUES ("111","40");
INSERT INTO mytable (user_id,money_earned) VALUES ("222","45");
INSERT INTO mytable (user_id,money_earned) VALUES ("222","1");
INSERT INTO mytable (user_id,money_earned) VALUES ("333","5");
INSERT INTO mytable (user_id,money_earned) VALUES ("333","19");
I need to know table has how many rows, how many different users, and how many times each user has earned.
I need this result:
TOTAL_ROWS: 7
TOTAL_INDIVIDUAL_USERS: 3
USER_ID USER_TIMES
111 3
222 2
333 2
Is your problem that you want the total as well? If so, then you can get this using rollup:
SELECT coalesce(cast(user_id as char(20)), 'TOTAL USER_TIMES'),
COUNT(*) as times
FROM mytable
GROUP BY user_id with rollup;
You can get the user counts in a separate column with this trick:
SELECT coalesce(cast(user_id as char(20)), 'TOTAL USER_TIMES'),
COUNT(*) as times, count(distinct user_id) as UserCount
FROM mytable
GROUP BY user_id with rollup;
You realize that a SQL query just returns a table of values. You are asking for very specific formatting, which is typically done better at the application level. That said, you can get close to what you want with something like this:
select user, times
from ((SELECT 3 as ord, cast(user_id as char(20)) as user, COUNT(*) as times
FROM mytable
GROUP BY user_id
)
union all
(select 1, 'Total User Count', count(*)
from mytable
)
union all
(select 2, 'Total Users', count(distinct user_id)
from mytable
)
) t
order by ord;
I think this could be a typo anyway your are trying to sum your COUNT() times, simply replace with money_earned
SELECT user_id,
COUNT(*) AS 'times',
SUM(money_earned) AS 'sum_money'
FROM mytable GROUP BY user_id;
SQL Fiddle
I create a temporary table #tbl(account, last_update). I have following two inserts from different source (could be tables from different databases) to insert account with last update date. For example
create table #tbl ([account] numeric(18, 0), [last_update] datetime)
insert into #tbl(account , last_update)
select table1.account, max(table1.last_update)
from table1 join…
group by table1.account
insert into #tbl(account , last_update)
select table2.account, max(table2.last_update)
from table2 join…
group by table2.account
The problem is this could cause duplicate account in the table #tbl. I either have to avoid it during each insert or remove the duplicate after both insert. Also, if there is account with two different last_update, I want the #tbl have the latest last_update. How do I achieve this conditional insert? Which one will have better performance?
Do you think you could rewrite your query to something like:
create table #tbl ([account] numeric(18, 0), [last_update] datetime)
insert into #tbl(account , last_update)
select theaccount, MAX(theupdate) from
(
select table1.account AS theaccount, table1.last_update AS theupdate
from table1 join…
UNION ALL
select table2.account AS theaccount, table2.last_update AS theupdate
from table2 join…
) AS tmp GROUP BY theaccount
The UNION ALL will build you 1 unique table combining table1 + table2 records. From there, you can act as if was a regular table, which means that you are able to find the max last_update for each record using a "group by"
insert into #tbl(account , last_update)
select account, last_update
from
(
select a.* from #table1 a where
last_update in( select top 1 last_update from #table1 b
where
a.account = b.account
order by last_update desc)
UNION
select a.* from #table2 a where
last_update in( select top 1 last_update from #table2 b
where
a.account = b.account
order by last_update desc)
) AS tmp