Say I have a rather large table in a Teradata database, "Sales" that has a daily record for every sale and I want to write a SQL statement that limits this to the latest date only. This will not always be the previous day, for example, if it was a Monday the latest date would be the previous Friday.
I know I can get the results by the following:
SELECT s.*
FROM Sales s
JOIN (
SELECT MAX(SalesDate) as SalesDate
FROM Sales
) sd
ON s.SalesDate=sd.SalesDt
I am not knowledgable on how it would process the subquery and since Sales is a large table would there be a more efficient way to do this given there is not another table I could use?
Another (more flexible) way to get the top n utilizes OLAP-functions:
SELECT *
FROM Sales s
QUALIFY
RANK() OVER (ORDER BY SalesDate DESC) = 1
This will return all rows with the max date. If you want only one of them switch to ROW_NUMBER.
That is probably fine, if you have an index on salesdate.
If there is only one row, then I would recommend:
select top 1 s.*
from sales s
order by salesdate desc;
In particular, this should make use of an index on salesdate.
If there is more than one row, use top 1 with ties.
Related
I have a sales data table with cust_ids and their transaction dates.
I want to create a table that stores, for every customer, their cust_id, their last purchased date (on the basis of transaction dates) and the count of times they have purchased.
I wrote this code:
SELECT
cust_xref_id, txn_ts,
DENSE_RANK() OVER (PARTITION BY cust_xref_id ORDER BY CAST(txn_ts as timestamp) DESC) AS rank,
COUNT(txn_ts)
FROM
sales_data_table
But I understand that the above code would give an output like this (attached example picture)
How do I modify the code to get an output like :
I am a beginner in SQL queries and would really appreciate any help! :)
This would be an aggregation query which changes the table key from (customer_id, date) to (customer_id)
SELECT
cust_xref_id,
MAX(txn_ts) as last_purchase_date,
COUNT(txn_ts) as count_purchase_dates
FROM
sales_data_table
GROUP BY
cust_xref_id
You are looking for last purchase date and count of distinct transaction dates ( like if a person buys twice, it should be considered as one single time).
Although you mentioned you want count of dates but sample data shows you want count of distinct dates - customer 284214 transacted 9 times but distinct will give you 7.
So, here is the SQL you can use to get your result.
SELECT
cust_xref_id,
MAX(txn_ts) as last_purchase_date,
COUNT(distinct txn_ts) as count_purchase_dates -- Pls note distinct will count distinct dates
FROM sales_data_table
GROUP BY 1
I need to program a query where I can see the changes that certain fields have undergone in a certain date period.
Example: From the CAM_CONCEN table bring those records where the ACCOUNT_NUMBER undergoes a modification in the CONCTACT field in a period of 6 months before the date.
I would be grateful if you can guide me.
You can use LAG() to peek at the previous row of a particular subset of rows (the same account in this case).
For example:
select *
from (
select c.*,
lag(contact) over(partition by account_number
order by change_date) as prev_contact
from cam_concen c
) x
where contact <> prev_contact
I'm new to SQL. Trying to get a certain date for jobs from a table. The only way to get these dates is to look to a massive table where every item for each job is stored with a last transaction date. The date I want is the largest date in the lst_trx_date column for each job.
The data in the table looks something like this:
Where each job has a varying amount of items. My biggest hurdle and my main question: How can I instead of selecting the entire job table only select the largest lst_trx_date for each job? I initially brought in the data using microsoft query, but I realize my request will probably require modifying the SQL command text directly.
Try something like this.. this will give you the max date
SELECT MAX (lst_trx_date) AS "Max Date"
FROM table where job = 1234;
To get the latest date for each job, you can use windowing functions. As an example try:
select job, item, lst_trx_date from (select job, item, lst_trx_date, row_number()
over(partition by stat,job,item order by
lst_trx_date desc) rn
from <table>)t
where rn = 1
I think it would be along these lines:
SELECT job, MAX(lst_trx_date) as job, last_transaction_date
FROM table
GROUP BY job
ORDER BY lst_trx_date DESC
I am trying to select all records in a time-variant Account table for each account with a change in an associated value (e.g. the maturity date). A change in the value will result in the most recent record for an account being end-dated and a new record (containing a new effective date of the following day) being created. The most recent records for accounts in this table have an end-date of 12/31/9000.
For instance, in the below illustration, account 44444444 would not be included in my query result set since it hasn't had a change in the value (and thus also has no additional records aside from the original); however, the other accounts have multiple changes in values (and multiple records), so I would want to see those returned.
I've tried using the row_num function, as well as a reflexive join, but for some reason I'm not getting the expected results. What are some ways to obtain the results I need?
Note: The primary key for this table includes the acct_id and eff_dt. Also, I'm using PostgreSQL in a Greenplum environment.
Here are two types of queries I tried to use but which produced problematic results:
Query 1
Query 2
If you want only the accounts, use aggregation:
select acct_id
from t
group by acct_id
having min(value) <> max(value);
Based on your description, you could also use count(*) >.
If you want the original records, you can use window functions:
select t.*
from (select t.*, count(*) over (partition by acct_id) as cnt
from t
) t
where cnt > 1;
I have some records track inquires by DATETIME. There is an glitch in the system and sometimes a record will enter multiple times on the same day. I have a query with a bunch of correlated subqueries attached to these but the numbers are off because when there were those glitches in the system then these leads show up multiple times. I need the first entry of the day, I tried fooling around with MIN but I couldn't quite get it to work.
I currently have this, I am not sure if I am on the right track though.
SELECT SL.UserID, MIN(SL.Added) OVER (PARTITION BY SL.UserID)
FROM SourceLog AS SL
Here's one approach using row_number():
select *
from (
select *,
row_number() over (partition by userid, cast(added as date) order by added) rn
from sourcelog
) t
where rn = 1
You could use group by along with min to accomplish this.
Depending on how your data is structured if you are assigning a unique sequential number to each record created you could just return the lowest number created per day. Otherwise you would need to return the ID of the record with the earliest DATETIME value per day.
--Assumes sequential IDs
select
min(Id)
from
[YourTable]
group by
--the conversion is used to stip the time value out of the date/time
convert(date, [YourDateTime]