I came up with this query to fill in a missing field from a second table using a subquery.
I can not modify the original table
SELECT
CASE WHEN original.target_field IS NULL THEN
(SELECT fill_in.target_field FROM second.table fill_in
WHERE original.id = fill_in.id)
ELSE
original.target_field END AS myField
FROM
primary.table original
I was wondering if I was missing something and if there was a more performant way to do this?
You could use LEFT JOIN and COALESCE instead of correlated subquery:
SELECT COALESCE(original.target_field,fill_in.target_field) AS myField
FROM primary.table original
LEFT JOIN second.table fill_in
ON original.id = fill_in.id
It is always worth testing different methods. But your query should be fine with an appropriate index.
I would write it as:
SELECT (CASE WHEN o.target_field IS NULL
THEN (SELECT f.target_field
FROM second.table f
WHERE o.id = f.id
)
ELSE o.target_field
END) AS myField
FROM primary.table o;
You want an index on second.table(id, target_field). You would want the same index for the LEFT JOIN version.
Related
Adding back some original info for historical purposes as I thought simplifying would help but it didn't. We have this stored procedure, in this part it is selecting records from table A (calldetail_reporting_agents) and doing a left join on table B (Intx_Participant). Apparently there are duplicate rows in table B being pulled that we DON'T want. Is there any easy way to change this up to only pick the first match on table B? Or will I need to rewrite the whole thing?
SELECT 'Agent Calls' AS CallType,
CallDate,
CallTime,
RemoteNumber,
DialedNumber,
RemoteName,
LocalUserId,
CallDurationSeconds,
Answered,
AnswerSpeed,
InvalidCall,
Intx_Participant.Duration
FROM calldetail_reporting_agents
LEFT JOIN Intx_Participant ON calldetail_reporting_agents.CallID = Intx_Participant.CallIDKey
WHERE DialedNumber IN ( SELECT DialedNumber
FROM #DialedNumbers )
AND ConnectedDate BETWEEN #LocStartDate AND #LocEndDate
AND (#LocQueue IS NULL OR AssignedWorkGroup = #LocQueue)
Simpler version: how to change below to select only first matching row from table B:
SELECT columnA, columnB FROM TableA LEFT JOIN TableB ON someColumn
I changed to this per the first answer and all data seems to look exactly as expected now. Thank you to everyone for the quick and attentive help.
SELECT 'Agent Calls' AS CallType,
CallDate,
CallTime,
RemoteNumber,
DialedNumber,
RemoteName,
LocalUserId,
CallDurationSeconds,
Answered,
AnswerSpeed,
InvalidCall,
Intx_Participant.Duration
FROM calldetail_reporting_agents
OUTER APPLY (SELECT TOP 1
*
FROM Intx_Participant ip
WHERE calldetail_reporting_agents.CallID = ip.CallIDKey
AND calldetail_reporting_agents.RemoteNumber = ip.ConnValue
AND ip.HowEnded = '9'
AND ip.Recorded = '0'
AND ip.Duration > 0
AND ip.Role = '1') Intx_Participant
WHERE DialedNumber IN ( SELECT DialedNumber
FROM #DialedNumbers )
AND ConnectedDate BETWEEN #LocStartDate AND #LocEndDate
AND (#LocQueue IS NULL OR AssignedWorkGroup = #LocQueue)
You can try to OUTER APPLY a subquery getting only one matching row.
...
FROM calldetail_reporting_agents
OUTER APPLY (SELECT TOP 1
*
FROM intx_Participant ip
WHERE ip.callidkey = calldetail_reporting_agents.callid) intx_participant
WHERE ...
You should add an ORDER BY in the subquery. Otherwise it isn't deterministic which row is taken as the first. Or maybe that's not an issue.
I have used a left join on two of my tables. Now I want to use case to identify the records from my left table who don't have a match in the right table. Such records exist and have a null value in the 'id_zeus' column of my join, however when I execute the case, it is as these fields don't exist. Where am I going wrong ? I get "Present" in all my column Disturbance. I am using Oracle SQL developer.
SELECT
CASE DP.ID_PRB
WHEN NULL
THEN 'Absence'
ELSE 'Present' END as Disturbance,
FROM
FIRE.WSITE WI
LEFT JOIN
(SELECT DISTINCT
DPL.ID_PERT as ID_PRB
FROM FIRE.DEPPLAN DPL
GROUP BY DPL.ID_PERT
) DPL
ON WI.ID_PERT = DP.ID_PERT
What is const? You don't seem to need it. The SELECT DISTINCT and GROUP BY are redundant, so use only one of them. And your alias on the subquery is incorrect.
But your problem is the comparison to NULL. It doesn't even match when doing a comparison as you are doing in CASE. You need to use IS NULL:
SELECT (CASE WHEN DP.ID_PRB IS NULL THEN 'Absence' ELSE 'Present'
END) as Disturbance,
FROM FIRE.WSITE WI LEFT JOIN
(SELECT DISTINCT DPL.ID_PERT as ID_PRB
FROM FIRE.OSI_DEVIATION_PLANS DP
) DP
ON WI.ID_PERT = DP.ID_PERT;
This query would commonly be written as:
SELECT (CASE WHEN NOT EXISTS (SELECT 1
FROM FIRE.OSI_DEVIATION_PLANS DP
WHERE WI.ID_PERT = DP.ID_PERT
)
THEN 'Absence' ELSE 'Present'
END) as Disturbance,
FROM FIRE.WSITE WI ;
This offers more opportunities for optimization.
I am trying to use a case statement with sub query in a Update statement but I am facing an Issue like
single-row sub query returns more than
Please find my Query which I tried
update r_gl.ac
set meeting_cost = case currency_code when 'IND'
then amount
else round(tgt.amount)
from r_gl.ac tgt
join
(
select distinct
a.frm_cur,
a.to_cur,
a.exch_rate
from b_gl.currncy_conv_dim a
join r_gl.ac b
on (a.frm_cur = 123 and a.to_cur = b.cur_cd and f_rate = 'ABC')
join b_gl.int_fg
on b.in_s=c.in_s and a.cal_sk = trunc(c.intact_dt_key,-2)
) src
on tgt.cur_cd=src.to_cur
)
end
Please help me to solve this issue
Your current CASE expression is missing its END. That aside, I see even bigger problems with your UPDATE statement. Redshift is based on an old version of Postgres, and hence I expect that it would adhere to the same syntax Postgres would use for an update join:
UPDATE table1 AS t1
SET some_column = t2.some_other_column
FROM table2 AS t2
WHERE t1.id = t2.id
Applying this syntax to your current query along with the fix for the CASE expression leaves us with the following:
update r_gl.ac tgt
set meeting_cost = case when currency_code = 'IND'
then tgt.amount
else round(tgt.amount) end
from
(
select distinct
a.frm_cur,
a.to_cur,
a.exch_rate
from b_gl.currncy_conv_dim a
inner join r_gl.ac b
on (a.frm_cur = 123 and a.to_cur = b.cur_cd and f_rate = 'ABC')
inner join b_gl.int_fg
on b.in_s=c.in_s and a.cal_sk = trunc(c.intact_dt_key,-2)
) src
where tgt.cur_cd = src.to_cur
The table to which you are joining r_gl.ac has no effect on the data being used to update, but rather would only affect the update by targeting certain rows. If this be not your intended logic, then you might have to rethink the entire query.
I'm writing a some filtering logic that basically wants to first check if there's a value in the filter table, then if there is return the filtered values. When there isn't a value in the filter table just return everything. The following table does this correctly but I have to write the same select statement twice.
select *
from personTbl
where (not exists (select filterValue from filterTable where filterType = 'name') or
personTbl.name in (select filterValue from filterTable where filterType = 'name'))
Is there some better way to do this that will return true if the table is empty, or the value is contained within it?
One approach is to do a left outer join to your filter-subquery, and then select all the rows where the join either failed (meaning that the subquery returned no rows) or succeeded and had the right value:
SELECT personTbl.*
FROM personTbl
LEFT
OUTER
JOIN ( SELECT DISTINCT filterValue
FROM filterTable
WHERE filterType = 'name'
) filter
ON 1 = 1
WHERE filter.filterValue = personTbl.name
OR filter.filterValue IS NULL
;
To be honest, I'm not sure if the above is a good idea — it's not very intuitive1, and I'm not sure how well it will perform — but you can judge for yourself.
1. As evidence of its unintuitiveness, witness the mistaken claim below that it doesn't work. As of this writing, that comment has garnered two upvotes. So although the query is correct, it clearly inspires people to great confidence that it's wrong. Which is a nice party trick, but not generally desirable in production code.
You can use a collection to try to make the query more intuitive (and only require a single select from the filter table):
CREATE TYPE filterlist IS TABLE OF VARCHAR2(100);
/
SELECT p.*
FROM PersonTbl p
INNER JOIN
( SELECT CAST(
MULTISET(
SELECT filterValue
FROM filterTable
WHERE filterType = 'name'
)
AS filterlist
) AS filters
FROM DUAL ) f
ON ( f.filters IS EMPTY OR p.name MEMBER OF f.filters );
I created a table and i am in the process of inserting rows from another table into it. However, some of these rows require joins from other tables. To my knowledge, this means using a subquery select statement in the statement. the problem is subqueries only return one result, where i may have many. I am wanting to return a -1 where no records exists. Here is an example i am using but it is not working:
INSERT INTO [BDW_ReportPrototype].[dbo].[CustomerCreditFact]
( [MortgageDimID]
,[LeaseDimID]
,[OREODimID]
,[OfficerTypeDimID] )
SELECT
--[MortgageDimID]
-2
--LeaseDimID
,-2
--OREODimID
,-2
,CASE WHEN OfficerTypeDimID IS NULL THEN -1 ELSE OfficerTypeDimID END
FROM Staging_FDB_LN_CPDM_Daily LCD
LEFT OUTER JOIN ERMA..OfficerTypeDim OTD on OTD.OfficerNum = LCD.OFFICER
FROM dbo.Staging_FDB_LN_CPDM_Daily
Try this sql statement
SELECT CASE WHEN OfficerTypeDimID IS NULL THEN -1 ELSE OfficerTypeDimID END
FROM Staging_FDB_LN_CPDM_Daily LCD
LEFT OUTER JOIN ERMA..OfficerTypeDim OTD on OTD.OfficerNum = LCD.OFFICER
I would rework your query like the following.
First of all, use a LEFT OUTER JOIN in your query instead of the subqueries. This type of join says a row might exist in the "other" table but it might not but I want a row back regardless.
Now that you know you'll have all your rows, you'll want to see if there is a value there or not. Use the shorthand and easier to maintain check via the coalesce function. It basically is a list of values (column names, variables or hard coded values) and the optimizer will pick the first non-null value from the list and use it. Here we supply -1 for your query
INSERT INTO
[BDW_ReportPrototype].[dbo].[CustomerCreditFact]
(
[OfficerTypeDimID]
)
SELECT
-- coalesce returns the first non-null value
COALESCE(OTD.OfficerTypeDimID, -1) AS OfficerTypeDimID
FROM
dbo.Staging_FDB_LN_CPDM_Daily LCD
LEFT OUTER JOIN
ERMA..OfficerTypeDim OTD
ON OTD.OfficerNum = LCD.OFFICER
maybe something along these lines...
INSERT INTO [BDW_ReportPrototype].[dbo].[CustomerCreditFact]
([OfficerTypeDimID])
Select OfficerTypeDimID
from ERMA..OfficerTypeDim OTD
inner JOIN Staging_FDB_LN_CPDM_Daily LCD
on OTD.OfficerNum = LCD.OFFICER
UNION ALL
SELECT -1
FROM dbo.Staging_FDB_LN_CPDM_Daily LCD
WHERE NOT EXISTS
(
Select OfficerTypeDimID from ERMA..OfficerTypeDim
OTD
WHERE
OTD.OfficerNum = LCD.OFFICER
)