I have two Tables. A & B
ID Name
1 A
2 B
3 C
4 D
and
ID Sal
1 400
2 300
3 500
Now I need to fetch the record (both ID, Name) from first table, those sal is not assigned in second table. Using sub query I got this. But i need to solve it without using sub query.
So I tried with minus operator. But I am getting full first table as it is.
select id,name from A
minus
select id,to_char(null) from B;
What am I doing wrong?
But without Using Sub Query i need to Solve.
Use this using CTE:
with tbl(id) as ( select id from B)
select id,name
from A
inner join tbl b
on a.id <> b.id
You can use the minus inside with clause
with ids as (
select id
from A
minus
select id
from B
) select A.id ,A.name
from A join ids on ids.userid=A.userid;
Related
I have two tables:
acc_num
ser_code
1
A
1
B
1
C
2
C
2
D
and the second one is:
ser_code
value
A
5
B
8
C
10
D
15
I want to exclude all the accounts with the service codes that they have value of 10 or 15.
Because my data set is huge, I want to use NOT EXIST but it just excludes combination of acc_num and ser_code.
I want to exclude the acc_num with all of it's ser_code, because on of it's ser_code meats my criteria.
I used:
select acc_num, ser_code
from table 1
where NOT EXIST (select 1
FROM table 2 where acc_num = acc_num and value in (10, 15)
out put with above code is:
acc_num
ser_code
1
A
1
B
Desire out put would be empty.
here you are
select t1.acc_num,t1.ser_code from table1 t1, table2 t2
where (t1.ser_code=t2.ser_code and t2.value not in (10,15))
and t1.acc_num not in
(
select t3.acc_num from table1 t3,table2 t4
where t1.acc_num=t3.acc_num and t3.ser_code=t4.ser_code
and t4.value in (10,15)
) ;
This could be achieved in many ways. However using NOT EXISTS is the best option. The problem with your query is for acc_num 1, there are ser_code that does not have value as 10, 15. So you will get A and B in result.
To overcome that you must pull acc_num inside the sub-query
Query 1 (using NOT EXISTS):
As you can see in the below query, I have included acc_num inside sub-query, so that the filter works properly,
SELECT DISTINCT a.acc_num, a.ser_code
FROM one as a
WHERE NOT EXISTS
(
SELECT DISTINCT one.acc_num
FROM two
INNER JOIN one
ON one.ser_code=two.ser_code
WHERE value IN (10,15) AND a.acc_num=one.acc_num
)
Query 2 (using LEFT JOIN):
NOT EXISTS often confusing due to it's nature (super fast though). Hence LEFT JOIN could also be used (expensive than NOT EXISTS),
SELECT DISTINCT a.acc_num, a.ser_code
FROM one as a
LEFT JOIN
(
SELECT DISTINCT one.acc_num
FROM two
INNER JOIN one
ON one.ser_code=two.ser_code
WHERE value IN (10,15)
) b
ON a.acc_num=b.acc_num
WHERE b.acc_num IS NULL
Query 3 (using NOT IN):
NOT IN would also achieve this with comprehensive query but expensive than both of the above methods,
SELECT DISTINCT a.acc_num, a.ser_code
FROM one as a
WHERE a.acc_num NOT IN
(
SELECT DISTINCT one.acc_num
FROM two
INNER JOIN one
ON one.ser_code=two.ser_code
WHERE value IN (10,15)
)
All 3 would yield same result. I would prefer to go with NOT EXISTS
See demo with time consumption in db<>fiddle
I have 3 tables. All of them have a column - id. I want to find if there is any value that is common across the tables. Assuming that the tables are named a.b and c, if id value 3 is present is a and b, there is a problem. The query can/should exit at the first such occurrence. There is no need to probe further. What I have now is something like
( select id from a intersect select id from b )
union
( select id from b intersect select id from c )
union
( select id from a intersect select id from c )
Obviously, this is not very efficient. Database is PostgreSQL, version 9.0
id is not unique in the individual tables. It is OK to have duplicates in the same table. But if a value is present in just 2 of the 3 tables, that also needs to be flagged and there is no need to check for existence in he third table, or check if there are more such values. One value, present in more than one table, and I can stop.
Although id is not unique within any given table, it should be unique across the tables; a union of distinct id should be unique, so:
select id from (
select distinct id from a
union all
select distinct id from b
union all
select distinct id from c) x
group by id
having count(*) > 1
Note the use of union all, which preserves duplicates (plain union removes duplicates).
I would suggest a simple join:
select a.id
from a join
b
on a.id = b.id join
c
on a.id = c.id
limit 1;
If you have a query that uses union or group by (or order by, but that is not relevant here), then you need to process all the data before returning a single row. A join can start returning rows as soon as the first values are found.
An alternative, but similar method is:
select a.id
from a
where exists (select 1 from b where a.id = b.id) and
exists (select 1 from c where a.id = c.id);
If a is the smallest table and id is indexes in b and c, then this could be quite fast.
Try this
select id from
(
select distinct id, 1 as t from a
union all
select distinct id, 2 as t from b
union all
select distinct id, 3 as t from c
) as t
group by id having count(t)=3
It is OK to have duplicates in the same table.
The query can/should exit at the first such occurrence.
SELECT 'OMG!' AS danger_bill_robinson
WHERE EXISTS (SELECT 1
FROM a,b,c -- maybe there is a place for old-style joins ...
WHERE a.id = b.id
OR a.id = c.id
OR c.id = b.id
);
Update: it appears the optimiser does not like carthesian joins with 3 OR conditions. The below query is a bit faster:
SELECT 'WTF!' AS danger_bill_robinson
WHERE exists (select 1 from a JOIN b USING (id))
OR exists (select 1 from a JOIN c USING (id))
OR exists (select 1 from c JOIN b USING (id))
;
I have two table:
A:
id code
1 A1
2 A1
3 B1
4 B1
5 C1
6 C1
=====================
B:
id Aid
1 1
2 4
(B doesn't contain the Aid which link to code C1)
Let me explain the overall flow:
I want to make each row in table A have different code(by delete duplicate),and I want to retain the Aid which I can find in table B.If Aid which not be saved in table B,I retain the id bigger one.
so I can not just do something as below:
DELETE FROM A
WHERE id NOT IN (SELECT MAX(id)
FROM A
GROUP BY code,
)
I can get each duplicate_code_groups by below sql statement:
SELECT code
FROM A
GROUP BY code
HAVING COUNT(*) > 1
Is there some code in sql like
for (var ids in duplicate_code_groups){
for (var id in ids) {
if (id in B){
return id
}
}
return max(ids)
}
and put the return id into a idtable?? I just don't know how to write such code in sql.
then I can do
DELETE FROM A
WHERE id NOT IN idtable
Using ROW_NUMBER() inside CTE (or sub-query) you can assign numbers for each Code based on your ordering and then just join the result-set with your table A to make a delete.
WITH CTE AS
(
SELECT A.*, ROW_NUMBER() OVER (PARTITION BY A.Code ORDER BY COALESCE(B.ID,0) DESC, A.ID desc) RN
FROM A
LEFT JOIN B ON A.ID = B.Aid
)
DELETE A FROM A
INNER JOIN CTE C ON A.ID = C.ID
WHERE RN > 1;
SELECT * FROM A;
SQLFiddle DEMO
The first select gives you all A.id that are in B - you don't want to delete them. The second select takes A, selects all codes without an id that appears in B, and from this subset takes the maximum id. These two sets of ids are the ones you want to keep, so the delete deletes the ones not in the sets.
DELETE from A where A.id not in
(
select aid from B
union
select MAX(A.id) from A left outer join B on B.Aid=A.id group by code having COUNT(B.id)=0
)
Actual Execution Plan on MS SQL Server 2008 R2 reveals that this solution performs quite well, it's 5-6 times faster than Nenad's solution :).
Try this Solution
DELETE FROM A
WHERE NOT id IN
(
SELECT MAX(B.AId)
FROM A INNER JOIN B ON A.id = B.aId
)
I have a table with data like so:
[ID, Name]
1, Bob
1, Joe
1, Joe
1, Bob
I want to retrieve a list of records showing the relationship between the records with the same ID.
For instance, I want the following result set from my query:
Bob, Joe
Joe, Bob
Bob, Bob
Joe, Joe
This shows me the "from" and "to" for every item in the table.
I can get this result by using the following query:
SELECT DISTINCT [NAME]
FROM TABLE A
INNER JOIN TABLE B ON A.ID = B.ID
Is there anyway for me to achieve the same result set without the use of the "distinct" in the select statement? If I don't include the distinct, I get back 16 records, not 4.
The reason you get duplicate rows without DISTINCT is because every row of ID = x will be joined with every other row with ID = x. Since the original table has (1, "Bob") twice, both of those will be joined to every row in the other table with ID = 1.
Removing duplicates before doing a join will do two things: decrease the time to run the query, and prevent duplicate rows from showing up in the result.
Something like (using MySQL version of SQL):
SELECT L.NAME, R.NAME
FROM (SELECT DISTINCT ID, NAME FROM A) AS L
INNER JOIN (SELECT DISTINCT ID, NAME FROM B) AS R
ON L.ID = R.ID
Edit: is B an alias for table A?
In SQL and MY SQL
SELECT COLUMN_NAME FROM TABLE_NAME group by COLUMN_NAME
Have you tried using a group by clause?
select name
from table a
inner join table b
on a.id=b.id
group by name
That should get you the same thing as your distinct query above. As for the result set that you want, a simple self join should do it:
select name1,name2
from(
select id,name as name1
from table
group by 1,2
)a
join(
select id,name as name2
from table
group by 1,2
)b
using(id)
Eliminating duplicate values with union without using distinct
Declare #TableWithDuplicateValue Table(Name Varchar(255))
Insert Into #TableWithDuplicateValue Values('Cat'),('Dog'),('Cat'),('Dog'),('Lion')
Select Name From #TableWithDuplicateValue
union
select null where 1=0
Go
Output
---------
Cat
Dog
Lion
For more alternate kindly visit my blog
http://www.w3hattrick.com/2016/05/getting-distinct-rows-or-value-using.html
I have two tables A and B where there is one-to-many relationship.
Now I want some records from A and with this existence field that shows if B has any matching records. I don't want to use the count function as B has too many records that delays SQL execution. Either I don't want to use proprietary keywords like rownum of Oracle like below, as I need as much compatibility as possible.
select A.*, (
select 1 from B where ref_column = A.ref_column and rownum = 1
) existence
...
You would use left join + count anyway, select statement in select list can be executed multiple times while join will be done only once.
Also you can consider EXISTS:
select A.*, case when exists (
select 1 from B where ref_column = A.ref_column and rownum = 1
) then 1 else 0 end
Use an EXISTS clause. If the foreign key in B is indexed, performance should not be an issue.
SELECT *
FROM a
WHERE EXISTS (SELECT 1 FROM b WHERE b.a_id = a.id)