I don't know if JPQL support the query like this(I am using EclipseLink 2.4.1):
select count(product.id if product.pics.count>0) as proWithPic,count(product.id if product.pics.count=0) as proWithoutPic from Product product group by product.brandName.
I know the syntax is ugly, please correct me.
Thanks
I would execute two queries.
select count(product.id) as proWithPic from Product product where size(product.pics) > 0 group by product.brandName
select count(product.id) as proWithoutPic from Product product where size(product.pics) = 0 group by product.brandName
There might be a way to execute them as a single query using sub-selects in the SELECT clause, or UNION, but two queries would be much simpler and probably perform better.
Related
I'm trying to build a sub-query with a list in the where clause, I have tried several variations and I think the problem is with the way I'm structuring the WHERE IN. Help is grealy appreciated!!
SELECT a.ACCT_SK,
a.BTN,
a.PRODUCT_SET,
MAX(b.ORD_CREATD_DT)
FROM MM.MEC_ACCT_ATTR a, CDI_CRM.ORD_MSTR b
WHERE a.ACCT_SK=b.ACCT_SK AND a.BTN=b.BTN
(SELECT b.ACCT_SK, b.ORD_CREATD_DT
FROM CDI_CRM.ORD_MSTR b
WHERE b.ACCT_SK IN ('44347714',
'44023302',
'43604964'));
SELECT Failed. 3706: (-3706)Syntax error: expected something between '(' and the 'SELECT' keyword
The desired output is a table with Product set for 50 ACCT_SKs with the most recent order date matched on ACCT_SK and BTN.
Sample data and desired results would really help. Your query doesn't make much sense, but I suspect you want:
SELECT a.ACCT_SK, a.BTN, a.PRODUCT_SET,
MAX(o.ORD_CREATD_DT)
FROM MM.MEC_ACCT_ATTR a JOIN
CDI_CRM.ORD_MSTR o
ON a.ACCT_SK = o.ACCT_SK AND a.BTN = o.BTN
WHERE a.ACCT_SK IN ('44347714', '44023302', '43604964')
GROUP BY a.ACCT_SK, a.BTN, a.PRODUCT_SET;
This returns the columns you want for the three specified accounts.
Notes:
Always use proper, explicit, standard JOIN syntax. Never use commas in the FROM clause.
Your subquery simply makes no sense. It is not connected to anything else in the query.
You are using an aggregation function (MAX()) so your query is an aggregation query and needs a GROUP BY.
Use meaningful table aliases. a makes sense for an accounts table, but b does not make sense for an orders table.
I wrote the query below as part of a larger query to create a table. As I'm new to SQL, this was done in a very step-by-step manner so that I could easily understand the individual steps in the query and what each part was doing.
However, I've now been tasked to make the below 2 parts of the query more efficient by joining them together, and this is where I'm struggling.
I feel like I should be creating a single table rather than 2 and that the single table should contain all of the columns/values that I require. However, I am not at all sure of the syntax required to make this happen or the order in which I need to re-write the query.
Is anyone able to offer any advice?
Many thanks
sys_type as (select nvl(dw_start_date,sysdate) date_updated, id, descr
from scd2.scd2_table_a
inner join year_month_period
on 1=1
WHERE batch_end_date BETWEEN dw_start_date and NVL(dw_end_date,sysdate)),
sys_type_2 as (select -1 as sys_typ_id,
'Unassigned' as sys_typ_desc,
sysdate as date_updated
from dual
union
select id as sys_typ_id, descr as sys_typ_desc, date_updated
from sys_type),
Assuming you are using Oracle database, the queries above seem fine. I don't think you can make them more efficient just by 'joining' them (joining defined very loosely here. Is there a performance issue?
I think you can get better results by tuning your first inline query 'sys_type'.
You have a cartesian product there. Do you need that? Why don't you put the condition in the where clause as the join clause?
Basically
sys_type as (select nvl(dw_start_date,sysdate) date_updated, id, descr
from scd2.scd2_table_a
inner join year_month_period
on (batch_end_date BETWEEN dw_start_date and NVL(dw_end_date,sysdate)))
I am new to SQL. Could anyone help me to figure out why the "Group By" Expression isn't working in this sql query? I get this error
ERROR at line 3:
ORA-00979: not a GROUP BY expression
The code I am using is
CREATE OR REPLACE VIEW CUSTOMER_LINE_ITEM AS
SELECT CUSTOMER_ORDER_CART_INFO.loginName,CUSTOMER_ORDER_CART_INFO.FirstName,
CUSTOMER_ORDER_CART_INFO.LastName,CUSTOMER_ORDER_CART_INFO.orderCartID,(lineItems.orderPrice*lineItems.qtyOrdered) AS TOTAL_ORDER
FROM CUSTOMER_ORDER_CART_INFO
INNER JOIN lineItems
ON CUSTOMER_ORDER_CART_INFO.orderCartID = lineItems.orderCartID
GROUP BY CUSTOMER_ORDER_CART_INFO.loginName,CUSTOMER_ORDER_CART_INFO.FirstName,
CUSTOMER_ORDER_CART_INFO.LastName,CUSTOMER_ORDER_CART_INFO.orderCartID
ORDER BY orderCartID;
Without the Group By expression I generate this view. I think the group by expression should just remove the duplicates and just give me the results with different order cart ID. Could anyone help me understand what I am doing wrong here?
VIEW of CUSTOMER_LINE_ITEM without 'group by'
The error is with group by clause. Remember simple rule of thumb, all columns being selected to be in group by clause, or the columns to be selected which are not part of group by clause are to be selected as some aggregate function, like, MAX, MIN, SUM, AVG, etc.
Try the following query, which would run without issue. But I can't say its logical correctness which you need to figure out on your requirement basis.
CREATE OR REPLACE VIEW customer_line_item AS
SELECT cac.loginName,
cac.FirstName,
cac.LastName,
cac.orderCartID,
(SUM(li.orderPrice) * SUM(li.qtyOrdered)) AS TOTAL_ORDER
FROM customer_order_cart_info cac
INNER JOIN lineItems li
ON cac.orderCartID = li.orderCartID
GROUP BY cac.loginName,
cac.FirstName,
cac.LastName,
cac.orderCartID
ORDER BY cac.orderCartID;
Now thing to note here is, li.orderPrice and li.qtyOrdered were being selected, but were neither in group by nor in a aggregate function.
The use of group by is that, the columns in group by clause are used to logically group your data. Here your data is grouped by loginName, firstname, lastname, ordercartid. But there is a probability that multiple orderprice and qty exist for each group, and SQL is not able to justify the grouping logic then. Per your query one requirement that I could think of was, you want find the total value of order for a customer in his cart. Hence, you are multiplying orderPrice with qtyOrdered. To achieve this, you need to multiply orderPrice and orderqty of each lineItem. Hence, what you need is a sum of (orderPrice*orderQty) group by lineItem(lineItemID/lineItemNo maybe, just a guess). For this one, give me some time, let me devise an example and I will edit my answer with that. Till then you try something like above.
The cause of the error message is that you don't aggregate (lineItems.orderPrice*lineItems.qtyOrdered).
The Oracle documentation tells us
SelectItems in the SelectExpression with a GROUP BY clause must
contain only aggregates or grouping columns.
That means you should aggregate TOTAL_ORDER by using e.g.
sum(lineItems.orderPrice*lineItems.qtyOrdered)
or whatever the requirement is.
I've seen the following example:
Let T be a table with 2 columns - [id,value] (both int)
Then:
SELECT * FROM T
WHERE id=(SELECT MAX(id) FROM T t2 where T.value=t2.value);
is equivalent to:
SELECT MAX(id) FROM T GROUP BY value
What is going on behind the scene? How can we refer to T1.value?
What is the meaning of T1.value=t2.value?
#JuanCarlosOropeza is correct, your premise is false. Those are not equivalent queries. The second query should error out. But more to the point. The purpose of the WHERE clause in the subquery is to restrict the rows in the subquery to the id from the outer query.
For what's going on behind the scenes, use the explain plan, which provides information about how the optimizer decides to get the data your query asks for.
I am trying to create view, But select statement from this view is taking more than 15 secs.How can i make it faster. My query for the view is below.
create view Summary as
select distinct A.Process_date,A.SN,A.New,A.Processing,
COUNT(case when B.type='Sold' and A.status='Processing' then 1 end) as Sold,
COUNT(case when B.type='Repaired' and A.status='Processing' then 1 end) as Repaired,
COUNT(case when B.type='Returned' and A.status='Processing' then 1 end) as Returned
from
(select distinct M.Process_date,M.SN,max(P.enter_date) as enter_date,M.status,
COUNT(case when M.status='New' then 1 end) as New,
COUNT(case when M.status='Processing' and P.cn is null then 1 end) as Processing
from DB1.dbo.Item_details M
left outer join DB2.dbo.track_data P on M.SN=P.SN
group by M.Process_date,M.SN,M.status) A
left outer join DB2.dbo.track_data B on A.SN=B.SN
where A.enter_date=B.enter_date or A.enter_date is null
group by A.Process_date,A.New,A.Processing,A.SN
After this view..my select query is
select distinct process_date,sum(New),sum(Processing),sum(sold),sum(repaired),sum(returned) from Summary where month(process_date)=03 and year(process_date)=2011
Please suggest me on what changes to be made for the query to perform faster.
Thank you
ARB
It is hard to give advices without seeing the actual data and the structure of the tables. I would rewrite the query keeping in mind these principles:
Use inner join instead of outer join if possible.
Get rid of case operator inside COUNT function. Build a query so you use conditions in WHERE section not in COUNT.
Try to not use aggregated values in GROUP BY. Currently you use aggregated values New and Processing for grouping. Use GROUP BY by existing table values if possible.
If the query gets too complicated, break it into smaller queries and combine results in the final query. Writing a store procedure may help in this case.
I hope this helps.
For tuning a database query, I shall add few items additional to what #Davyd has already listed:
Look at the tables and indexing on those tables. Putting the right index and avoiding the wrong ones always speed up the query.
Is there anything in the where condition that is not part of any index? At times we put index on a column and in the query we use a cast or convert on the column. So the underlying index is not effective. You may consider setting the index on the cast/convert of the column.
Look at the normal form conformity or over normalisation. 3.
Good luck.
If your are using Postgresql, I suggest you use a tool like "http://explain.depesz.com/" in order to see more clearly what part of your query is slow. Depending on what you get, you could either optimize your indexes, or rewrite part of your query. If your are using another database, I'm sure a similar tool exists.
If none of these ideas help, the final solution would be to create a "materialized query". There are plenty of infos on the web regarding this.
Good luck.