Starting with 2 tables, I want to get all rows with value in a certain column(cName) that is present on 1 table but not the other. I want to do this for both tables. I found a solution to use LEFT JOIN which gives me solution for 1 of the tables and I used UNION to combine. Is this a good way to do this or is there a better way?
select *
from College C1 LEFT JOIN myTestTable T1 on C1.cName = T1.cName
where T1.cName IS NULL
UNION
select *
from myTestTable T1 LEFT JOIN College C1 on T1.cName = C1.cName
where C1.cName IS NULL
You can use full join with a where:
SELECT *
FROM College C1 FULL JOIN
myTestTable T1
ON C1.cName = T1.cName
WHERE T1.cName IS NULL OR C1.cName IS NULL;
I prefer anti-join (NOT EXISTS) operators rather than LEFT JOIN. For one, if CName is not unique the left join produces multiple rows which the UNION must eliminate.
select * from College C1
WHERE NOT EXISTS (SELECT 1 FROM myTestTable T1 WHERE C1.cName = T1.cName)
UNION
select * from myTestTable T1
WHERE NOT EXISTS (SELECT 1 FROM College C1 WHERE T1.cName = C1.cName);
If indexes aren't available on CName you'll have some table scans with either LEFT JOIN or the NOT EXISTS.
You could also do this:
select * from College
union all
select * from myTestTable
MINUS ( select * from College intersect select * from myTestTable );
Related
I don't know, if I made good title, but please let me visualize this.
So I have two tables and for given case I need to select row where payment currency was ONLY in EUR.
Correct document Id's will be: 2, 3, 4, 5
These are overall bigger tables with 900k+ records.
Can you please suggest me how query should look?
use correlated subquery with not exists
select distinct a.document_id from tablename a inner join tablename b b on a.document_id=b.payment_docid
where not exists
(select 1 from tablename b1 where b1.payment_docid=b.payment_docid and currency<>'EUR')
Try this query:
select payment_docId from MyTable
group by payment_docId
having max(currency) = 'EUR'
and min(currency) = 'EUR'
or you could use having count(*) = 1 with min or max as well.
use corelated subquery
select t1.* from table2 as t1
where exists( select 1 from table2 t2 where t1.payment_docid=t2.payment_docid
having count(distinct currency)=1)
and currency='EUR'
It is possible to use INNER JOIN with the following conditions to get all rows:
SELECT
pd.payment_doc_id
, pd.currency
FROM DocTable dt
INNER JOIN PaymentDocs pd
ON dt.document_id = pd.payment_doc_id AND pd.currency IN ('EUR')
If you want distinct rows, then you can apply operator GROUP BY:
SELECT
pd.payment_doc_id
, pd.currency
FROM DocTable dt
INNER JOIN PaymentDocs pd
ON dt.document_id = pd.payment_doc_id AND pd.currency IN ('EUR')
GROUP BY pd.payment_doc_id
, pd.currency
Aggregation is the only efficient want :
select doc_id
from table t
group by doc_id
having min(currency) = max(currency) and min(currency) = 'EUR';
The DB I'm working with has three tables with identical column layouts, OPEX, NOPEX and CAPEX. I would like to query all three for items with a matching AssetId and get a single result set so that I can process them all at the same time in my .Net code.
The twist is that I do need to know which table they came from.
I know I can do this with a series of CASE in the SELECT clause, perhaps using the ID column in each where it's non-zero to decide which of the tables it came from. But I would have to have one for each column and the tables are pretty wide.
Is there some other way to solve this problem?
In order to get them into one set, you would use a combination of UNION and EXISTS() checks. The UNION ALL will give you a single result set that contains data from all three tables, and the EXISTS check on each will confirm the table you are querying from has corresponding records in the other tables.
SELECT *, 'OPEX' AS table_name
FROM OPEX o
WHERE EXISTS (
SELECT 1
FROM NOPEX n
WHERE n.asset_id = o.asset_id)
AND EXISTS (
SELECT 1
FROM CAPEX c
WHERE c.asset_id = o.asset_id)
UNION ALL
SELECT *, 'NOPEX' AS table_name
FROM NOPEX n
WHERE EXISTS (
SELECT 1
FROM Opex o
WHERE o.asset_id = n.asset_id)
AND EXISTS (
SELECT 1
FROM CAPEX c
WHERE c.asset_id = n.asset_id)
UNION ALL
SELECT *, 'CAPEX' AS table_name
FROM CAPEX c
WHERE EXISTS (
SELECT 1
FROM Opex o
WHERE o.asset_id = c.asset_id)
AND EXISTS (
SELECT 1
FROM NOPEX n
WHERE n.asset_id = c.asset_id)
I guess you could also do INNER JOINs?
SELECT c.*, 'CAPEX' AS table_name
FROM CAPEX c
INNER JOIN OPEX o
ON o.asset_id = c.asset_id
INNER JOIN NOPEX n
ON n.asset_id = c.asset_id
UNION ALL
SELECT o.*, 'OPEX' AS table_name
FROM OPEX o
INNER JOIN CAPEX c
ON c.asset_id = o.asset_id
INNER JOIN NOPEX n
ON n.asset_id = o.asset_id
UNION ALL
SELECT n.*, 'NOPEX' AS table_name
FROM NOPEX n
INNER JOIN OPEX o
ON o.asset_id = n.asset_id
INNER JOIN CAPEX c
ON c.asset_id = n.asset_id
Similar answer to dfundako, but resolving sooner where AssetId is in all three tables and less hitting of the indexes on the related tables:
;with cte as (
select
AssetID
from (
select distinct
AssetID
from Opex
union all
select distinct
AssetID
from Nopex
union all
select distinct
AssetID
from Capex
) as AssetIDs
group by AssetId
having count(AssetId) = 3
)
select 'Opex', * from Opex as o
inner join cte
on o.AssetID = cte.AssetID
union all
select 'Nopex', * from Nopex as n
inner join cte
on n.AssetID = cte.AssetID
union all
select 'Capex', * from Capex as c
inner join cte
on c.AssetID = cte.AssetID
is there a way to improve this query..
INSERT INTO mastertable
VALUES (SELECT *
FROM staging_tbl s
WHERE s.pac NOT IN (SELECT pac
FROM mastertable)
AND s.store NOT IN (SELECT store
FROM mastertable))
Not sure if this will work at first place.. Basically..want to select records from Staging_Tbl only if same PAC-STORE combination do not currently exist.. If PAC exist but for another STORE..yes, we should select and vice versa.
For eg: Should if MasterTable is as below,
PAC1 STORE1
PAC1 STORE2
PAC2 STORE1
PAC2 STORE2
I should insert only if there is a record like PAC1 STORE3 in the staging table..
and NOT PAC1 STORE2
Do you have indexes on those columns..that will make a change
you can also use NOT EXISTS
INSERT INTO MASTERTABLE
SELECT * FROM Staging_Tbl S
WHERE NOT EXISTS ( SELECT 1 FROM MasterTable M
WHERE S.STORE = M.STORE
AND S.PAC = M.PAC)
Or A LEFT JOIN
INSERT INTO MASTERTABLE
SELECT S.* FROM Staging_Tbl S
LEFT OUTER JOIN MasterTable M
ON S.STORE = M.STORE
AND S.PAC = M.PAC
WHERE M.PAC IS NULL
AND M.STORE IS NULL
Except, make sure to test performance with this one
INSERT INTO MASTERTABLE
SELECT * FROM Staging_Tbl
EXCEPT
SELECT * FROM MASTERTABLE
I myself like NOT EXISTS the best
See also Select all rows from one table that don't exist in another table for usage of OUTER APPLY and EXCEPT to do the same
INSERT MASTERTABLE
SELECT * FROM Staging_Tbl S
WHERE NOT EXISTS
(SELECT 1 FROM MASTERTABLE M
WHERE M.PAC = S.PAC AND M.STORE = S.STORE)
I have two tables with the same structure:
id name
1 Merry
2 Mike
and
id name
1 Mike
2 Alis
I need to union second table to first with keeping unique names, so that result is:
id name
1 Merry
2 Mike
3 Alis
Is it possible to do this with MySQL query, without using php script?
This is not a join (set multiplication), this is a union (set addition).
SELECT #r := #r + 1 AS id, name
FROM (
SELECT #r := 0
) vars,
(
SELECT name
FROM table1
UNION
SELECT name
FROM table2
) q
This will select all names from table1 and combine those with all the names from table2 which are not in table1.
(
select *
from table1
)
union
(
select *
from table2 t2
left join table1 t1 on t2.name = t1.name
where t1.id is null
)
Use:
SELECT a.id,
a.name
FROM TABLE_A a
UNION
SELECT b.id,
b.name
FROM TABLE_B b
UNION will remove duplicates.
As commented, it all depends on what your 'id' means, cause in the example, it means nothing.
SELECT DISTINCT(name) FROM t1 JOIN t2 ON something
if you only want the names
SELECT SUM(something), name FROM t1 JOIN t2 ON something GROUP BY name
if you want to do some group by
SELECT DISTINCT(name) FROM t1 JOIN t2 ON t1.id = t2.id
if the id's are the same
SELECT DISTINCT COALESCE(t1.name,t2.name) FROM
mytable t1 LEFT JOIN mytable t2 ON (t1.name=t2.name);
will get you a list of unique names from the 2 tables. If you want them to get new ids (like Alis does in your desired results), that's something else and requires the answers to a couple of questions:
do any of the names need to maintain their previous id. And if they do, which table's id should be preferred?
why do you have 2 tables with the same structure? ie what are you trying to accomplish when you generate the unique name list?
I have a Join
SELECT * FROM Y
INNER JOIN X ON ISNULL(X.QID, 0) = ISNULL(y.QID, 0)
Isnull in a Join like this makes it slow. It's like having a conditional Join.
Is there any work around to something like this?
I have a lot of records where QID is Null
Anyone have a work around that doesn't entail modifying the data
You have two options
INNER JOIN x
ON x.qid = y.qid OR (x.qid IS NULL AND y.qid IS NULL)
or easier
INNER JOIN x
ON x.qid IS NOT DISTINCT FROM y.qid
If you want null values to be included from Y.QID then Fastest way is
SELECT * FROM Y
LEFT JOIN X ON y.QID = X.QID
Note: this solution is applicable only if you need null values from Left table i.e. Y (in above case).
Otherwise
INNER JOIN x ON x.qid IS NOT DISTINCT FROM y.qid
is right way to do
This article has a good discussion on this issue. You can use
SELECT *
FROM Y
INNER JOIN X ON EXISTS(SELECT X.QID
INTERSECT
SELECT y.QID);
Are you committed to using the Inner join syntax?
If not you could use this alternative syntax:
SELECT *
FROM Y,X
WHERE (X.QID=Y.QID) or (X.QUID is null and Y.QUID is null)
I'm pretty sure that the join doesn't even do what you want. If there are 100 records in table a with a null qid and 100 records in table b with a null qid, then the join as written should make a cross join and give 10,000 results for those records. If you look at the following code and run the examples, I think that the last one is probably more the result set you intended:
create table #test1 (id int identity, qid int)
create table #test2 (id int identity, qid int)
Insert #test1 (qid)
select null
union all
select null
union all
select 1
union all
select 2
union all
select null
Insert #test2 (qid)
select null
union all
select null
union all
select 1
union all
select 3
union all
select null
select * from #test2 t2
join #test1 t1 on t2.qid = t1.qid
select * from #test2 t2
join #test1 t1 on isnull(t2.qid, 0) = isnull(t1.qid, 0)
select * from #test2 t2
join #test1 t1 on
t1.qid = t2.qid OR ( t1.qid IS NULL AND t2.qid IS NULL )
select t2.id, t2.qid, t1.id, t1.qid from #test2 t2
join #test1 t1 on t2.qid = t1.qid
union all
select null, null,id, qid from #test1 where qid is null
union all
select id, qid, null, null from #test2 where qid is null
Hey it is kind of late to answer that but I got the same question, what I realized is that you must have a record with the ID of 0 in you second table to make this :
SELECT * FROM Y
INNER JOIN X ON ISNULL(Y.QID, 0) = ISNULL(X.QID, 0)
to happen, it actually says if there is none, then use 0. BUT what if Y table does NOT have a record with the ID of 0?
So, I found this method, (and worked for my case):
SELECT
ISNULL(Y.QName, 'ThereIsNone') AS YTableQName
FROM
X
LEFT OUTER JOIN Y ON X.QID = Y.QID
A snapshot of my case
This way you DON'T need a record with 0 ID value in your second table (which is Y in this case and Customers in my case), OR any record at all
UPDATE:
You can also take a look at this post for better understanding.
Basically you want to join two tables together where their QID columns are both not null, correct? However, you aren't enforcing any other conditions, such as that the two QID values (which seems strange to me, but ok). Something as simple as the following (tested in MySQL) seems to do what you want:
SELECT * FROM `Y` INNER JOIN `X` ON (`Y`.`QID` IS NOT NULL AND `X`.`QID` IS NOT NULL);
This gives you every non-null row in Y joined to every non-null row in X.
Update: Rico says he also wants the rows with NULL values, why not just:
SELECT * FROM `Y` INNER JOIN `X`;
You could also use the coalesce function. I tested this in PostgreSQL, but it should also work for MySQL or MS SQL server.
INNER JOIN x ON coalesce(x.qid, -1) = coalesce(y.qid, -1)
This will replace NULL with -1 before evaluating it. Hence there must be no -1 in qid.