Hello I Have a problem in getting rows from one table after comparing both. Detail of Both Table are as follows:-
I am using Ms Access database.
TableA is having a data of numeric type (Field Name is A it is primary key)
----------
Field A
==========
1
2
3
4
5
Table B is having data of numeric type ( Field Name is A it is foreign key)
--------
Field A
========
2
4
Now I am using below query which is this
select a.a
from a a
, b b
where a.a <> b.b
I want to show all the data from Table A which is not equal to Table B. But the above query is not working as I described.
Can you help me in this regard.
Regards,
Fawad Munir
In an attempt at clarity, I've used upper case for tables and lower case for fields:
Select A.a
FROM A LEFT OUTER JOIN B ON A.a=B.b
WHERE B.b is null
This will show all the records in A that are not in B (I assume that's what you want).
Read up on Access outer joins. In the query designer you double click the join and select something like "all records from table a and only the matching records in table b".
In your question you said that the name of the field in table B is 'A'. Given that, I'd say that your query should be something like
select a.a
from a, b
where a.a <> b.a
But I'm not sure this will do what you want. I think you're trying to find rows in table A which do not have a matching row in table B, in which case you might try
SELECT A.A
FROM A
LEFT OUTER JOIN B
ON (B.A = A.A)
WHERE B.A IS NULL
Try that and see if it does what you want.
Share and enjoy.
I don't know exactly if Access would accept the syntax, but here how I would do in SQL Server.
select a.a
from TableA a
where a.a NOT IN (
select b.a
from TableB b
)
or even as above-mentioned:
select a.a
from TableA a
left outer join TableB b on b.a = a.a
where b.a IS NULL
Its not entirely clear what you are trying to achieve, but its sounds like you are attempting to solve the common problem of finding rows in Table A missing associated data in Table B. If this is the case, it appears you misunderstand the semantics of the join you tried. In which case, you have 2 problems, because the understanding the the JOIN operation is critical to working with relational databases.
In relation to the first problem, please research how to express a subquery using the IN operator. Something like
... WHERE a NOT IN (SELECT a from b)
In relation to the second problem, try your query without the WHERE restriction, and see what is returned. Once you understand what the join is doing, you will see why applying a WHERE restriction to it will not solve your problem.
If I understand you correctly, you want to see every row in A for which column a contains a value that cannot be found in any column b value of B. You can get this data in several ways.
I think using NOT IN is the clearest, personally:
SELECT * FROM tableA WHERE columnA NOT IN
(SELECT columnB FROM tableB WHERE columnB IS NOT NULL)
Many people prefer a filtered JOIN:
SELECT tableA.* FROM tableA LEFT OUTER JOIN tableB
ON tableA.columnA = tableB.columnB WHERE tableB.columnB IS NULL
There is a NOT EXISTS variant as well:
SELECT * FROM tableA WHERE columnA NOT EXISTS
(SELECT * FROM tableB WHERE columnB = tableA.columnA)
Related
Using Snowflake,have 2 tables, one with many columns and the other with a few, trying to select * on their join, get the following error:
SQL compilation error:duplicate column name
which makes sense because my joining columns are in both tables, could probably use select with columns names instead of *, but is there a way I could avoid that? or at least have the query infer the columns names dynamically from any table it gets?
I am quite sure snowflake will let you choose all from both halves of two+ tables via
SELECT a.*, b.*
FROM table_a AS a
JOIN table_b AS b
ON a.x = b.x
what you will not be able to do is refer to the named of the columns in GROUP BY indirectly, thus this will not work
SELECT a.*, b.*
FROM table_a AS a
JOIN table_b AS b
ON a.x = b.x
ORDER BY x
even though some databases know because you have JOIN ON a.x = b.x there is only one x, snowflake will not allow it (well it didn't last time I tried this)
but you can with the above use the alias name or the output column position thus both the following will work.
SELECT a.*, b.*
FROM table_a AS a
JOIN table_b AS b
ON a.x = b.x
ORDER BY a.x
SELECT a.*, b.*
FROM table_a AS a
JOIN table_b AS b
ON a.x = b.x
ORDER BY 1 -- assuming x is the first column
in general the * and a.* forms are super convenient, but are actually bad for performance.
when selecting you are now are risk of getting the columns back in a different order if the table has been recreated, thus making reading code unstable. Which also impacts VIEWs.
It also means all meta data for the table need to be loaded to know what the complete form of the data will be in. Where if you want x,y,z only and later a w was added to the table, the whole query plan can be compiled faster.
Lastly if you are selecting SELECT * FROM table in a sub-select and only a sub-set of those columns are needed the execution compiler doesn't need to prune these. And if all variables are attached to a correctly aliased table, if later a second table adds the same named column, naked columns are not later ambiguous. Which will only occur when that SQL is run, which might be an "annual report" which doesn't happen that often. wow, what a long use alias rant.
You can prefix the name of the column with the name of the table:
select table_a.id, table_b.name from table_a join table_b using (id)
The same works in combination with *:
select table_a.id, table_b.* from table_a join table_b using (id)
It works in "join" and "where" parts of the statement as well
select table_a.id, table_b.* from table_a join table_b
on table_a.id = table_b.id where table_b.name LIKE 'b%'
You can use table aliases to make the statement sorter:
select a.id, b.* from table_a a join table_b b
on a.id = b.id
Aliases could be applies on fields to use in subqueries, client software and (depending on the SQL server) in the other parts of the statements, for example 'order by':
select a.id as a_id, b.* from table_a a join table_b b
on a.id = b.id order by a_id
If you're after a result that includes all the distinct non-join columns from each table in the join with the join columns included in the output only once (given they will be identical for an inner-join) you can use NATURAL JOIN.
e.g.
select * from d1 natural inner join d2 order by id;
See examples: https://docs.snowflake.com/en/sql-reference/constructs/join.html#examples
I face issue about duplicate data when join table, here my sample data table I have
-- Table A
I want to join with
-- Table B
this my query notation for join both table,
select a.trans_id, name
from tableA a
inner join tableB b
on a.ID_Trans = b.trans_id
and this the result, why I get the duplicating data which should show only two lines of data, please help me to solve this case.
Firstly, as you have been told multiple times in the comments, this is working exactly as you have written, and (more importantly) as intended. You have 2 rows in tableA and those 2 rows match 2 rows in your table tableB according to the ON clause. This means that each join operation, for the each of the rows in tableA, results in 2 rows as well; thus 4 rows (2 * 2 = 4).
Considering that your table, TableA only has one column then it seems that you should be cleaning up that data and deleting the duplicates. There are plenty of examples on how to do that already (example).
Perhaps the column you show us in TableA is one many, and thus instead you have a denormalisation issue, and instead there should be another table with the details of Id_trans and a PRIMARY KEY or UNIQUE CONSTRAINT/INDEX on it. Then you would join fron that table to TableB.
Finally, what you might be after is an EXISTS, which would look like this:
SELECT B.trans_id, B.[name]
FROM dbo.TableB B
WHERE EXISTS(SELECT 1
FROM dbo.TableA A
WHERE A.ID_Trans = B.trans_id); --Odd that it's called ID_Trans in one table, and Trans_ID in another
As the comments mentioned your query does exactly what you asked it to do but I think you wanted something like:
select a.trans_id, a.name, b.name
from tableA a
inner join tableB b on a.trans_id = b.trans_id
group by a.trans_id, a.name, b.name
Since there are two rows in both table with same ID join will make them four. You can use distinct to remove duplicates:
select distinct a.trans_id, name
from tableA a
inner join tableB b
on a.id_trans = b.trans_id
But I would suggest to use exists:
select trans_id, name
from tableB b
exists (select 1 from tableA a where a.trans_id=b.trans_id)
I have an empty table that I would like to fill with rows from a second table, based off a third table, Ill call them A,B,C respectively.
Table C has ID numbers that match ID numbers for rows in Table B. For every ID in table C, I want to add the corresponding row from table B into Table A.
This is what I have, and I am getting an error saying that I cannot use the last statement.
INSERT INTO TABLEA
SELECT * FROM TABLEB
WHERE ID FROM TABLEB = ID FROM TABLEC;
DSNT408I SQLCODE = -199, ERROR: ILLEGAL USE OF KEYWORD FROM. TOKEN ( . AT
MICROSECONDS MICROSECOND SECONDS SECOND MINUTES MINUTE WAS EXPECTED
DSNT418I SQLSTATE = 42601 SQLSTATE RETURN CODE
Any help would be appreciated.
INSERT INTO TableA
SELECT B.*
FROM TableB AS B
JOIN TableC AS C ON B.ID = C.ID
Or possibly that will give you too many duplicates (if there are multiple rows in C that match a given row in B), in which case you might need:
INSERT INTO TableA
SELECT B.*
FROM TableB AS B
WHERE B.ID IN (SELECT C.ID FROM TableC AS C)
Or:
INSERT INTO TableA
SELECT DISTINCT B.*
FROM TableB AS B
JOIN TableC AS C ON B.ID = C.ID
Both of those give you one row in A for each row in B that matches one or more rows in C.
How would I add a WHEN clause to this? Let's say Table C has another column called VALUE, and I want to add all the ID numbers that have a value of 'x' or greater. How would I do that, I tried adding JOIN TableC AS C ON B.ID = C.ID AND C.VALUE > 5 but I still got all the values from TABLE C.
Working with the first query (fixing the others being left as an 'exercise for the reader'), then what I think you should be doing is just:
INSERT INTO TableA
SELECT B.*
FROM TableB AS B
JOIN TableC AS C ON B.ID = C.ID
WHERE C.Value > 5
The optimizer should translate that to an equivalent expression:
INSERT INTO TableA
SELECT B.*
FROM TableB AS B
JOIN TableC AS C ON B.ID = C.ID AND C.Value > 5
I'm not clear from your comment whether you somehow added a second reference to TableC in the one query, or you modified your query as shown in this second example. If you were not using LEFT JOIN anywhere, then adding the AND C.Value > 5 term to the ON clause or as a WHERE clause should have yielded the correct data.
When debugging this sort of problem, it is worth noting that this INSERT statement has a perfectly good SELECT statement in it that you can run on its own to review what is going to be added to TableA. You might want to augment the select-list to include (at least) C.ID and C.Value just to make sure nothing is going haywire.
I'm a newbie, just learning SQL and have this question: I have two tables with the same columns. Some registers are in the two tables but others only are in one of the tables. To illustrate, suppose table A = (1,2,3,4), table B=(3,4,5,6), numbers are registers. I need to select all registers in table B if they are not in table A, that is result=(5,6). What query should I use? Maybe a join. Thanks.
You can either use a NOT IN query like this:
SELECT col from A where col not in (select col from B)
or use an outer join:
select A.col
from A LEFT OUTER JOIN B on A.col=B.col
where B.col is NULL
The first is easier to understand, but the second is easier to use with more tables in the query.
Select register from TABLE_B b
Where not exists (Select register from TABLE_A a where a.register = b.register)
I assumed you have a column named register in TABLE_A and TABLE_B
I was wondering, is there a way to make a kind of one to one left outer join:
I need a join that matches say table A with table B, for each record on table A it must search for its pair on table B, but there exists only 1 record that matches that condition, so when it has found its pair on B, it must stop and continue with the next row at table A.
What I have is a simple LEFT OUTER JOIN.
select * from A left outer join B on A.ID = B.ID order by (NAME) asc
Thanks in advance!
SQL doesn't work this way. In the first place it does not look at things row-by-row. In the second place what defines the record you want to match on?
Assuming you don't really care which row is selcted, something like this might work:
SELECT *
From tableA
left outer join
(select b.* from tableb b1
join (Select min(Id) from tableb group by id) b2 on b1.id - b2.id) b
on a.id = b.id
BUt it still is pretty iffy that you wil get the records you want when there are multiple records with the id in table b.
The syntax you present in your question is correct. There is no difference in the query for joining on a one-to-one relationship than on a one-to-many.