Can I do this?:
SELECT * FROM calendar ORDER BY ((month * 31) + day)
Yes (assuming that you have numeric columns in your table called month and day)
Wouldn't you want
SELECT * FROM calendar ORDER BY ((`month` * 31) + `day`)
though?
Edit
Actually just use
SELECT * FROM calendar ORDER BY `month`, `day`
Unless I'm missing something?
You can order by any column in your query result. If you can SELECT such on-the-fly prepared information then you can ORDER BY it.
If you have columns in your table called month and day, then you should make a few changes to your query and it will work:
SELECT * FROM calendar ORDER BY ((month * 100) + day)
I removed the quotes from your column names and increased your month multiplier by one order of magnitude in order to ensure correct sorting on month and day numbers greater than or equal to 10. Also, I corrected a typo in the spelling of ORDER.
BUT
Your query will not sort correctly by year (not sure if this matters in your use case).
Your query will execute slowly on large data sets because of the dynamic nature of your ORDER by clause. Consider using a single date column and creating an index on it.
Related
I'm not sure if I'm asking this question right, but hopefully I can explain it well enough. I have a table that has a Date, Value, and WeekEndDate column. I want to create a sequence column that counts the distinct weeks from 1-13 and cycles every 13 weeks.
I attached a small sample of the output I'm trying to create. Is this even possible?
Use dense_rank() and some arithmetic:
select t.*,
((dense_rank() over (order by weekEnd) - 1) % 13) + 1
from t;
I have a table with some columns and a date column (that i made a partition with)
For example
[Amount, Date ]
[4 , 2020-4-1]
[3 , 2020-4-2]
[5 , 2020-4-4]
I want to get the latest Amount based on the Date.
I thought about doing a LIMIT 1 with ORDER BY, but, is that optimized by BigQuery or it will scan my entire table?
I want to avoid costs at all possible, I thought about doing a query based on the date today, and if nothing found search for yesterday, but I don't know how to do it in only one query.
Below is for BigQuery Standard SQL
#standardSQL
SELECT ARRAY_AGG(amount ORDER BY `date` DESC LIMIT 1)[SAFE_OFFSET(0)]
FROM `project.dataset.table`
WHERE `date` >= DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY)
Note: above assumes your date field is of DATE data type.
If your date field is a partition, you can use it in WHERE clause to filter which partitions should be read in your query.
In your case, you could do something like:
SELECT value
FROM <your-table>
WHERE Date >= DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY)
ORDER BY Data DESC
LIMIT 1
This query basically will:
Filter only today's and yesterday's partitions
Order the rows by your Date field, from the most recent to the older
Select the first element of the ordered list
If the table has a row with today's date, the query will return the data for today. If it dont't, the query will return the data for yesterday.
Finally, I would like to attach here this reference regarding querying partitioned tables.
I hope it helps
The LIMIT order stops the query whet it gets the amount of results indicated.
I think the query should be something like this, I'm not sure if "today()-1" returns
SELECT Amount
FROM <table> as t
WHERE date(t.Date) = current_date()
OR date(t.Date) = makedate(year(current_date()), dayofyear(current_date())-1);
Edited: Sorry, my answer is for MariaDB I now see you ask for Google-BigQuery which I didn't even know, but it looks like SQL, I hope it has some functions like the ones I posted.
I am attempting to pull month end balances from all accounts a customer has for every month. Here is what I've written. This runs correctly and gives me what I want—but it also runs extremely slowly. How would you recommend speeding it up?
SELECT DISTINCT
[AccountNo]
,SourceDate
,[AccountType]
,[AccountSub]
,[Balance]
FROM [DW].[dbo].[dwFactAccount] AS fact
WHERE SourceDate IN (
SELECT MAX(SOURCEDATE)
FROM [DW].[dbo].[dwFactAccount]
GROUP BY MONTH(SOURCEDATE),
YEAR (SOURCEDATE)
)
ORDER BY SourceDate DESC
I'd try a window function:
SELECT * FROM (
SELECT
[AccountNo]
,[SourceDate]
,[AccountType]
,[AccountSub]
,[Balance]
,ROW_NUMBER() OVER(
PARTITION BY accountno, EOMONTH(sourcedate)
ORDER BY sourcedate DESC
) as rn
FROM [DW].[dbo].[dwFactAccount]
)x
WHERE x.rn = 1
The row number will establish an incrementing counter in order of sourcedate descending. The counter will restart from 1 when the month in sourcedate changes (or the account number changes) thanks to the EOMONTH function quantising any date in a given month to be the last date of the month (2020-03-9 12:34:56 becomes 2020-03-31, as do all other datetimes in March). Any similar tactic to quantise to a fixed date in the month would also work such as using YEAR(sourcedate), MONTH(sourcedate)
You need to build a dimension table for the date with Date as PK, and your SourceDate in the fact table ref. that date dimension table.
Date dimension table can have month, year, week, is_weekend, is_holiday, etc. columns. You join your fact table with the date dimension table and you can group data using any columns in date table you want.
Your absolute first step should be to view the execution plan for the query and determine why the query is slow.
The following explains how to see a graphical execution plan:
Display an Actual Execution Plan
The steps to interpreting the plan and optimizing the query are too much for an SO answer, but you should be able to find some good articles on the topic by Googling. You could also post the plan in an edit to your question and get some real feedback on what steps to take to improve query performance.
I have a table with create_dt times and i need to get records but without the datas that have similar create_dt time (15 minutes).
So i need to get only one record instead od two records if the create_dt is in 15 minutes of the first one.
Format of the date and time is '(29.03.2019 00:00:00','DD.MM.YYYY HH24:MI:SS'). Thanks
It's a bit unclear what exactly you want, but one thing I can think of, is to round all values to the nearest "15 minute" and then only pick one row from those "15 minute" intervals:
with rounded as (
select create_dt,
date '0001-01-01' + (round((cast(create_dt as date) - date '0001-01-01') * 24 * 60 / 15) * 15 / 60 / 24) as rounded,
... other columns ....
from your_table
), numbered as (
select create_dt,
rounded,
row_number() over (partition by rounded order by create_dt) as rn
... other columns ....
from rounded
)
select *
from numbered
where rn = 1;
The expression date '0001-01-01' + (round((cast(create_dt as date) - date '0001-01-01') * 24 * 60 / 15) * 15 / 60 / 24) will return create_dt rounded up or down to the next "15 minutes" interval.
The row_number() then assigns unique numbers for each distinct 15 minutes interval and the final select then always picks the first row for that interval.
Online example: https://dbfiddle.uk/?rdbms=oracle_11.2&fiddle=e6c7ea651c26a6f07ccb961185652de7
I'm going to walk you through this conceptually. First of all, there's a difficulty in doing this that you might not have noticed.
Let's say you wanted one record from the same hour or day. But if there are two record created on the same day, you only want one in your results. Which one?
I mention this because to the designers of SQL, there is not a single answer that they can provide SQL to pick. Then cannot show data from both records without both records being in the tabular output.
This is a common problem, but when the designers of SQL provided a feature to handle it, it can only work if there is no ambiguity of how to have one row of result for two records. That solution is GROUP BY, but it only works for showing the fields other than the timestamp if they are the same for all the records which match the time period. You have to include all the fields in your select clause and if multiple records in your time period are the same, they will create multiple records in your output. So although there is a tool GROUP BY for this problem, you might not be able to use it.
So here is the solution you want. If multiple records are close together, then don't include the records after the first one. So you want a WHERE clause which will exclude a record if another record recently proceeds it. So the test for each record in the result will involve other records in the table. You need to join the table to itself.
Let's say we have a table named error_events. If we get multiples of the same value in the field error_type very close to the time of other similar events, we only want to see the first one. The SQL will look something like this:
SELECT A.*
FROM error_events A
INNER JOIN error_events B ON A.error_type = B.error_type
WHERE ???
You will have to figure out the details of the WHERE clause, and the functions for the timestamp will depend you when RDBMS product you are using. (mysql and postgres for instance may work differently.)
You want only the records where there is no record which is earlier by less then 15 minutes. You do want the original record. That record will match itself in the join, but it will be the only record in the time period between its timestamp and 15 minutes prior.
So an example WHERE clause would be
WHERE B.create_dt BETWEEN [15 minutes before A.create_dt] and A.create_dt
GROUP BY A.*
HAVING 1 = COUNT(B.pkey)
Like we said, you will have to find out how your database product subtracts time, and how 15 minutes is represented in that difference.
I have a table that I would like to sort by a timestamp desc and then compare all consecutive rows to determine the difference between each row. From there, I would like to find all the rows whose difference is greater than ~2hours.
I'm stuck on how to actually compare consecutive rows in a table. Any help would be much appreciated.
I'm using Oracle SQL Developer 3.2
You didn't show us your table definition, but something like this:
select *
from (
select t.*,
t.timestamp_column,
t.timestamp_column - lag(timestamp_column) over (order by timestamp_column) as diff
from the_table t
) x
where diff > interval '2' hour;
This assumes that timestamp_column is defined as timestamp not date (otherwise the result of the difference wouldn't be an interval)