I am getting blank value with this query from sql server
SELECT TOP 1 Amount from PaymentDetails WHERE Id = '5678'
it has no row,that is why its returning blank,So I want if no row then it should return 0
I already tried with COALESCE ,but its not working
how to solve this?
You are selecting an arbitrary amount, so one method is aggregation:
SELECT COALESCE(MAX(Amount), 0)
FROM PaymentDetails
WHERE Id = '5678';
Note that if id is a number, then don't use single quotes for the comparison.
To be honest, I would expect SUM() to be more useful than an arbitrary value:
SELECT COALESCE(SUM(Amount), 0)
FROM PaymentDetails
WHERE Id = '5678';
You can wrap the subquery in an ISNULL:
SELECT ISNULL((SELECT TOP 1 Amount from PaymentDetails WHERE Id = '5678' ORDER BY ????),0) AS Amount;
Don't forget to add a column (or columns) to your ORDER BY as otherwise you will get inconsistent results when more than one row has the same value for Id. If Id is unique, however, then remove both the TOP and ORDER BY as they aren't needed.
You should never, however, use TOP without an ORDER BY unless you are "happy" with inconsistent results.
Related
Simplified example:
In hive, I have a table t with two columns:
Name, Value
Bob, 2
Betty, 4
Robb, 3
I want to do a case when that uses the total of the Value column:
Select
Name
, CASE
When value>0.5*sum(value) over () THEN ‘0’
When value>0.9*sum(value) over () THEN ‘1’
ELSE ‘2’
END as var
From table
I don’t like the fact that sum(value) over () is computed twice. Is there a way to compute this only once. Added twist, I want to do this in one query, so without declaring user variables.
I was thinking of scalar queries:
With total as
(Select sum(value) from table)
Select
Name
, CASE
When value>0.5*(select * from total) THEN ‘0’
When value>0.9*(select * from total)THEN ‘1’
ELSE ‘2’
END as var
From table;
But this doesn’t work.
TLDR: Is there a way to simplify the first query without user variables ?
Don't worry about that. Let the optimizer worry about it. But, you can use a subquery or CTE if you don't want to repeat the expression:
select Name,
(case when value > 0.5 * total then '0'
when value > 0.9 * total then '1'
else '2'
end) as var
From (select t.*, sum(value) over () as total
from table t
) t;
Cross join a subquery that fetches the sum to the table:
Select
t.Name
, CASE
When t.value>0.9*tt.value THEN '1'
When t.value>0.5*tt.value THEN '0'
ELSE '2'
END as var
From table t cross join (select sum(value) value from table) tt
and change the order of the WHEN clauses in the CASE expression because as they are, the 2nd case will never succeed.
Since I/O is the major factor the slows down Hive queries, we should strive to reduce the num of stages to get better performance.
So it's better not to use a sub-query or CTE here.
Try this SQL with a global window clause:
select
name,
case
when value > 0.5*sum(value) over w then '0'
when value > 0.9*sum(value) over w then '1'
else '2'
end as var
from my_table
window w as (ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
In this case window clause is the recommended way to reduce repetition of code.
Both the windowing and the sum aggregation will be computed only once. You can run explain select..., confirming that only ONE meaningful MR stage will be launched.
Edit:
1. A simple select clause on a subquery is not sth to worry about. It can be pushed down to the last phase of the subquery, so as to avoid additional MR stage.
2. Two identical aggregations residing in the same query block will only be evaluated once. So don’t worry about potential repeated calculation.
I am attempting to filter my table and get the item that sold for the most amount of money. In order to do this I am using "AuctionOpen" to determine whether or not the auction is still open. The auction cannot be open and have the item been sold (later I will use this for the most expensive item available).
I am able to use the AND operator to compare AuctionOpen by using the following:
select s.*
from auctionsite.dbo.Auction s
where s.HighestBid = (select max(s2.HighestBid) from auctionsite.dbo.Auction
s2) and s.AuctionOpen = 0;
When I set this equal to zero I get results, but when I set it equal to 1, it only returns the column titles even though there are values set to 1 in the table.
Results when compared to 0:
Results when compared to 1:
Clearly, the highest bid is on a record where AuctionOpen <> 1.
I recommend using order by and fetch (or the equivalent in your database):
select s.*
from auctionsite.dbo.Auction s
where s.AuctionOpen = 0
order by s.HIghestBid desc
fetch first 1 row only
In SQL Server, use either select top (1) or offset 0 rows fetch first 1 row only.
I think you should try the Count aggregate function
here, try this:
**Select count(Item_name) As
[Item with the highest money]
from table_name
Group by Item_name DSEC;**
You can check my page hereSQL/MySQL tips for some SQL/MySQL lessons
I have a database people that looks like this:
I wanted to count the occurrences of state='CA'.
My first attempt was:
SELECT COUNT(state='CA')
FROM people
;
this returned 1 row with a value of 1000. So I thought that there were 1000 people from CA in the database.
This turns out to be incorrect. I know that they are 127, which I can verify with the query
SELECT COUNT(*)
FROM people
WHERE state='CA'
;
which returns 1 row with a value of 127.
I understand how the second query works. However, I do not understand what is wrong with the first one. What is it returning?
If you want to see what's going on, run the query:
select state='CA' from people;
You will see that you will get one result for each row in people, with the value 0 or 1 (or True/False). What you've selected is whether state='CA' for each row, and there will be just as many of those results as there are rows.
You can't constrain a COUNT statement within the statement, you have to do that via the WHERE clause as in your second example.
count is not a sum .. your first query is improper because don't return the number of the rows true .. but the total numbers of not null rows true or false
if you want a filter count you must use a where condition (as your second query) otherwise you must use an if or a a select case inside the sum() function eg:
Select sum(case
when state='CA' then 1 else 0
end) as my_result from People;
or if you want count .. use null and not 0min count
Select count(case
when state='CA' then 1 else null
end) as my_result from People;
Try this-:
Select count(case when state='CA' then 1 else null end) as xyz from People;
1st query will work if you use case when in side count,
like below query will returned count of CA
SELECT sum( case when state='CA' then 1 else 0 end)
FROM people
In first query it is assigning the value 'CA' to the column state for all 1000 rows instead of filtering the values. That is what SELECT does. SELECT does not filter the number of returning rows, it modifies the data.
Whereas in WHERE clause the rows are being filtered first then the SELECT clause runs the COUNT function.
There is a sequence for running the query. It starts from FROM then WHERE, GROUP BY, ORDER BY at the end SELECT will run.
To answer the actual question - why do you get 1000? I'm guessing that there are 1000 rows in your database, or at least 1000 where state is not null. Count will return the number of rows where the thing inside the () is not null and as one of your comments says, the part inside your () will return either true or false, neither of which is null, so will count them all. Your second example is of course the right way to do it.
I have the below query. The problem is the last column productdesc is returning two records and the query fails because of distinct. Now i need to add one more column in where clause of the select query so that it returns one record. The issue is that the column i need
to add should not be a part of group by clause.
SELECT product_billing_id,
billing_ele,
SUM(round(summary_net_amt_excl_gst/100)) gross,
(SELECT DISTINCT description
FROM RES.tariff_nt
WHERE product_billing_id = aa.product_billing_id
AND billing_ele = aa.billing_ele) productdescr
FROM bil.bill_sum aa
WHERE file_id = 38613 --1=1
AND line_type = 'D'
AND (product_billing_id, billing_ele) IN (SELECT DISTINCT
product_billing_id,
billing_ele
FROM bil.bill_l2 )
AND trans_type_desc <> 'Change'
GROUP BY product_billing_id, billing_ele
I want to modify the select statement to the below way by adding a new filter to the where clause so that it returns one record .
(SELECT DISTINCT description
FROM RRES.tariff_nt
WHERE product_billing_id = aa.product_billing_id
AND billing_ele = aa.billing_ele
AND (rate_structure_start_date <= TO_DATE(aa.p_effective_date,'yyyymmdd')
AND rate_structure_end_date > TO_DATE(aa.p_effective_date,'yyyymmdd'))
) productdescr
The aa.p_effective_date should not be a part of GROUP BY clause. How can I do it? Oracle is the Database.
So there are multiple RES.tariff records for a given product_billing_id/billing_ele, differentiated by the start/end dates
You want the description for the record that encompasses the 'p_effective_date' from bil.bill_sum. The kicker is that you can't (or don't want to) include that in the group by. That suggests you've got multiple rows in bil.bill_sum with different effective dates.
The issue is what do you want to happen if you are summarising up those multiple rows with different dates. Which of those dates do you want to use as the one to get the description.
If it doesn't matter, simply use MIN(aa.p_effective_date), or MAX.
Have you looked into the Oracle analytical functions. This is good link Analytical Functions by Example
I'm using MS SQL, and here is my query...
SELECT SUM(Quantity) FROM table1
WHERE [item_no]='0052556'
AND [qty_to_ship] > 0
AND [type] = 5
Interestingly, the query as it stands above returns 'NULL'...however, if I remove either one of the last 2 conditions it works fine (returns a real number)
to clarify, these queries work fine:
SELECT SUM(Quantity) FROM table1
WHERE [item_no]='0052556'
AND [type] = 5
and
SELECT SUM(Quantity) FROM table1
WHERE [item_no]='0052556'
AND [qty_to_ship] > 0
also note: 'type' is a PK, int, not null
what might be causing this?
Do you have a record that fullfils all the requirement in your (most restrictive) WHERE?
If not - there's your anwer.
Edit: RedFilter's comment is correct is well. You can add your own logic (ISNULL, etc.) in the SELECT Portion to change NULL to values you like (like 0, for instance)
Simply, there are no records that match both clauses
[qty_to_ship] > 0
AND [type] = 5
or the records that do match contain NULL in the Quantity field.
Please check if the below query returns you any rows.
SELECT * FROM table1
WHERE [item_no]='0052556'
AND [qty_to_ship] > 0
AND [type] = 5
If this is returning you atleast one row, then the SUM should not return NULL