I have two tables, one contains a list of items which is called watch_list with some important attributes and the other is just a list of prices which is called price_history. What I would like to do is group together 10 of the lowest prices into a single column with a group_concat operation and then create a row with item attributes from watch_list along with the 10 lowest prices for each item in watch_list. First I tried joins but then I realized that the operations where happening in the wrong order so there was no way I could get the desired result with a join operation. Then I tried the obvious thing and just queried the price_history for every row in the watch_list and just glued everything together in the host environment which worked but seemed very inefficient. Now I have the following query which looks like it should work but it's not giving me the results that I want. I would like to know what is wrong with the following statement:
select w.asin,w.title,
(select group_concat(lowest_used_price) from price_history as p
where p.asin=w.asin limit 10)
as lowest_used
from watch_list as w
Basically I want the limit operation to happen before group_concat does anything but I can't think of a sql statement that will do that.
Figured it out, as somebody once said "All problems in computer science can be solved by another level of indirection." and in this case an extra select subquery did the trick:
select w.asin,w.title,
(select group_concat(lowest_used_price)
from (select lowest_used_price from price_history as p
where p.asin=w.asin limit 10)) as lowest_used
from watch_list as w
Related
I'm inserting data into table from another table using below query in Teradata and I want to run this statement until table reaches 20GB. So I want to run below statement in a loop to achieve that. However I written one but it's giving query invalid error when I'm trying to execute. Could you please help me as I'm new to Teradata. Thanks.
insert into schema1.xyx select * from schema2.abc;
if/loop/etc. are only allowed in Stored Procedures.
Looping a billion times will be quite inefficient (and will result in much more than 20GB). Better check the current size of table abc from dbc.TableSizeV, calculate how many loops you need and then cross join.
insert into schema1.xyx
select t.*
from schema2.abc AS t
cross join
( -- calculated number of loops
select top 100000 *
-- any table with a large number of rows
from sys_calendar_calendar
);
But much easier is using sampling.
Calculate the number of rows needed and then
insert into schema1.xyx
select *
from schema2.abc
sample with replacement 100000000;
In ClickHouse, is there any way use the topK query on more than the column ,
for example:
select topK(10)(AGE,COUNTRY) ...
meaning I want the top10 combinations of AGE+COUNTRY,
I only found a workaround using concat on fields and topK on them, wondered if there is any other way.
You can pass array (or tuple) of columns to topK:
SELECT topK(10)([Age, Country])
FROM table
Or use the straightforward calculation (it is much slower but provides the exact result):
SELECT
Age,
Country
FROM table
GROUP BY
Age,
Country
ORDER BY count() DESC
LIMIT 10
I have two tables, one has single entries like this:
'rs47' 1027
The other has ranges:
'gene1' 1000 1500
These tables are huge, so I am trying to figure out the most efficient way to get all entries from table 1 where the entries are within any range in table 2.
I don't think that INTERSECT can be used like this. I know how to use SELECT to do this for a single entry:
SELECT name FROM 'table2' INDEXED BY 'start_end' WHERE 1027 BETWEEN start AND end
But I am not sure how to do that for every record in a table. Any ideas?
To check whether corresponding rows exist in the other table, you can use a correlated subquery:
SELECT *
FROM Table1
WHERE EXISTS (SELECT 1
FROM Table2
WHERE Table1.Value BETWEEN Table2.StartValue AND Table2.EndValue);
This is a pretty simple question that I haven't been able to find an answer for. Is it possible to have two separate SELECT commands (from the same table) in the same SqlDataSource command to populate two different cells in a given GridView?
I haven't been able to find current information so far.
::EDIT::
The challenge is that I'm attempting to manupulate one cell with a COUNT command and the second cell with a numerical grand total from the same information.
You can Combine results from two separate SELECT Statements by doing something like this..
SELECT X.A , Y.B
FROM (SELECT Column1 AS A FROM TableName) X, (SELECT Column2 AS B FROM TableName) Y
So I know enough SQL just to be really dangerous (I don't normally work the back-end) but cannot get the following view to be created successfully ;) The result set I'm after is a data set that has rows assigned as a column alias from multiple tables (instead of a 1xN flat of all columns). There is a many-to-one relationship when looking at the main table, based on foreign keys associated to the row id of the appropriate related table.
Ideally I'd like a data set that looks like this in the return:
dataset.transaction_row[n]: col1, col2, col3, coln... (columns from the transaction table)
dataset.category_row[n]: col1, co2, col3, coln... (columns from the category table)
and so on...
I get the following error:
Query Error: near "AS": syntax error Unable to execute statement
From:
CREATE VIEW view_unreconciled_transactions
AS SELECT account_transaction.* AS transaction_row,
category.* AS category_row,
memorized.name_rule_replace OR account_transaction.name AS payee
FROM account_transaction
LEFT JOIN memorized ON account_transaction.memorized_key = memorized.id
LEFT JOIN category ON account_transaction.category_key = category.id
WHERE status != 2
ORDER BY account_transaction.dt_posted DESC
It seems easy enough since the result-column selector is repeatable which includes expressions (referencing sqlite's syntax diagrams). In reference to the error, I'm assuming it's complaining about the 2nd 'AS' where I'm trying to get table.* assigned as an alias. Any help in the right direction is appreciated. If I had to, I suppose I could explicitly state all columns but that feels like a kludge.
The AS modifier can only be applied to a single column, not to a collection such as the * you used. You will have to break them out into specific names, (which is best practice IMHO anyway)
It looks like you want to make a "pivot table". They can be tricky to make in a database. I can say that if you a data result, where each row comes from a different table source, and the columns form each table are IDENTICAL, then you could try using a UNION statement to join the different results together like they are just one dataset.
NOTE that the columns all take their naming cue from the first dataset in a UNION and the datatype all need to be the same.