I am writing a simple select statement to compare two different tables.
table 1 table 2
a a
b b
c c
H d
e
f
I need to select any item in table 1 that does not exist in table 2.
You have a few options, one of which is
select table1.col from table1 where
not exists (select col from table2 where table2.col = table1.col)
SELECT table_1.name
FROM table_1
LEFT JOIN table_2 ON table_1.name = table_2.name
WHERE table_2.name IS NULL
Subquery should do it:
Select * from table1
where Id not in
(select distinct col from table2)
Since it looks like there is only one column.
Try this.
select * from table a -- select all of the things in a
minus
select * from table b -- remove from it the things in b
Related
I have below table join and noticed that Hive keeps two copies of the pk column - one from table b and one from table c. Is there a way to keep only 1 of those columns?
I can always replace select * with exact select column1, column2 etc but that wont be too efficient
with a as (
select
*
from table1 b left join table2 c
on b.pk = c.pk
)
select
*
from a;
;
#update 1
is it possible to alias many columns?
for example the below line works
select b.pk as duplicate_pk
but is there a way to do something like
select b.* as table2 to add text table2 before all the columns of the table b?
Not sure if you already tried this but you can choose what to select using either
b.* to select cols of only table1
c.* to select cols of only table2
Example:
with a as (
select
b.*
from table1 b left join table2 c
on b.pk = c.pk
)
select
*
from a;
Need your help to know if possible to select values from a table with the below condition :
Table content : matching between 2 objects
(Id_obj_A; name_obj_A; country_obj_A; Id_obj_B; name_obj_B; country_obj_B)
Select *
from table
Where (only if country_obj_A <> country_obj_B)
Many thanks for your help
Yes. There are a few ways, one is to use NOT EXISTS like this:
select
*
from tableA
where NOT EXISTS (
select NULL
from tableB
where tableB.country_obj_B = tableA.country_obj_A
)
or, using NOT IN
select
*
from tableA
where country_obj_A NOT IN (
select country_obj_B
from tableB
)
or, using a LEFT JOIN then exclude the joined rows:
select
*
from tableA
left join tableB on tableA.country_obj_A = tableB.country_obj_B
where tableB.country_obj_B IS NULL
Table A:
id Name
1 a
2 b
3 c
4 d
5 e
Table B:
id Name
3 c
4 d
5 e
Here, id is the primary key connected to Table B.
I need output like this:-
id
1
2
That means, which ids in Table A are not present in Table B
Use EXCEPT operator:
select id from tableA
except
select id from tableB
You can use a left join, which will preserve all records on the left side and associate them with null if no matching record is available on the right side.
This way you can then filter on the right side columns to be null to get the desired outcome
select t1.id
from tableA t1
left join
tableB t2
on t1.id = t2.id
where t2.id is null
Use NOT EXISTS in WHERE clause
SELECT id FROM TableA A
WHERE NOT EXISTS(SELECT 1 FROM TableB B WHERE A.id = B.Id )
Using Not in statement.
Try this:-
Select id from TableA
where id not in (Select id from TableB);
You can use minus:
select * from tableA
minus
select * from tableB
I have two tables
Table A:
ID
1
2
3
4
Table B:
ID
1
2
3
I have two requests:
I want to select all rows in table A that table B doesn't have, which in this case is row 4.
I want to delete all rows that table B doesn't have.
I am using SQL Server 2000.
You could use NOT IN:
SELECT A.* FROM A WHERE ID NOT IN(SELECT ID FROM B)
However, meanwhile i prefer NOT EXISTS:
SELECT A.* FROM A WHERE NOT EXISTS(SELECT 1 FROM B WHERE B.ID=A.ID)
There are other options as well, this article explains all advantages and disadvantages very well:
Should I use NOT IN, OUTER APPLY, LEFT OUTER JOIN, EXCEPT, or NOT EXISTS?
For your first question there are at least three common methods to choose from:
NOT EXISTS
NOT IN
LEFT JOIN
The SQL looks like this:
SELECT * FROM TableA WHERE NOT EXISTS (
SELECT NULL
FROM TableB
WHERE TableB.ID = TableA.ID
)
SELECT * FROM TableA WHERE ID NOT IN (
SELECT ID FROM TableB
)
SELECT TableA.* FROM TableA
LEFT JOIN TableB
ON TableA.ID = TableB.ID
WHERE TableB.ID IS NULL
Depending on which database you are using, the performance of each can vary. For SQL Server (not nullable columns):
NOT EXISTS and NOT IN predicates are the best way to search for missing values, as long as both columns in question are NOT NULL.
select ID from A where ID not in (select ID from B);
or
select ID from A except select ID from B;
Your second question:
delete from A where ID not in (select ID from B);
SELECT ID
FROM A
WHERE NOT EXISTS( SELECT 1
FROM B
WHERE B.ID = A.ID
)
This would select 4 in your case
SELECT ID FROM TableA WHERE ID NOT IN (SELECT ID FROM TableB)
This would delete them
DELETE FROM TableA WHERE ID NOT IN (SELECT ID FROM TableB)
SELECT ID
FROM A
WHERE ID NOT IN (
SELECT ID
FROM B);
SELECT ID
FROM A a
WHERE NOT EXISTS (
SELECT 1
FROM B b
WHERE b.ID = a.ID)
SELECT a.ID
FROM A a
LEFT OUTER JOIN B b
ON a.ID = b.ID
WHERE b.ID IS NULL
DELETE
FROM A
WHERE ID NOT IN (
SELECT ID
FROM B)
I have a table containing a unique ID field. Another field (REF) contains a reference to another dataset's ID field.
Now I have to select all datasets where REF points to a dataset that doesn't exist.
SELECT * FROM table WHERE ("no dataset with ID=REF exists")
How can I do this?
3 ways
SELECT * FROM YourTable y WHERE NOT EXISTS
(SELECT * FROM OtherTable o WHERE y.Ref = o.Ref)
SELECT * FROM YourTable WHERE Ref NOT IN
(SELECT Ref FROM OtherTable WHERE Ref IS NOT NULL)
SELECT y.* FROM YourTable y
LEFT OUTER JOIN OtherTable o ON y.Ref = o.Ref
WHERE o.Ref IS NULL
See also Five ways to return all rows from one table which are not in another table
Try this:
SELECT * FROM TABLE WHERE NOT EXISTS
(SELECT * FROM OtherTable WHERE TABLE.Ref = OtherTable.ID)
I think this should work
SELECT * FROM table WHERE id NOT IN (SELECT ref_id FROM ref_table)
or with JOIN
SELECT table.*
FROM table LEFT JOIN ref_table ON table.id = ref_table.ref_id
WHERE ref_table.ref_id IS NULL
SELECT
table1.*
FROM
table1
LEFT JOIN table2 ON table1.id = table2.ref
WHERE
table2.ref IS NULL
You can do a subquery like:
select * from table where somefield not in (select otherfield from sometable where ID=REF)
SELECT *
FROM table
WHERE ((SELECT COUNT(*) FROM table2 WHERE table2.id = table.ref) = 0)
Something like that :
SELECT * FROM table WHERE ID NOT IN(SELECT REF FROM Table2 )
Yes you can use
select * from x where not exist ( select * from y )