I'm working with an access database and I have some tables set up like this.
Table1(Table1Id, Field1, Field2, ...)
Table2(Table2Id, Table1Id, AuditDate, Field1, Field2, ...)
I am trying to select every record in Table1, and those in Table2 with the latest AuditDate. If there is no entry in Table2 to tie back into Table1, I just want to populate a row of what is in Table1 and a bunch of empty fields where the data from Table2 would come from. Here is the query I have so far.
SELECT Table1.TableId,
Table1.Field1,
Table1.Field2,
Table2.Field1,
Table2.Field2
FROM Table1
LEFT OUTER JOIN Table2 ON Table1.TableId = Table2.Table1Id
WHERE Table2.AuditDate = (SELECT MAX(AuditDate) FROM Table2 WHERE Table1.TableId = Table2.Table1Id)
The problem with this is that it only returns two records. There are only two entries in Table2 but I want it to return a row of data for every record in Table1 as well instead of just the ones that find a match in Table2.
The problem is this line:
WHERE Table2.AuditDate = ...
In cases where no Table2 entry exists, AuditDate will be NULL. So you need to test for that:
WHERE Table2.Table2Id IS NULL OR Table2.AuditDate = ...
Guess that if you remove the outer you would get every entry from table 1.
Edit: but if you have more entries in Table 2 than in Table 1 it will still be a problem.
Maybe try a Full JOIN?
Related
I want to get a value from an IN subquery with two columns, without needing to do two queries.
Sample:
SELECT * FROM table1 WHERE id IN(SELECT id, flags FROM table2);
Now I want to get flags directly. Is it possible, and if yes, how?
Any help is appreciated :)
It sounds like you are trying to achieve one of two things:
1) Select every field of records in table1 (and the associated table 2 flag) where the record's id is also found in the id column of table2. If that is the case, then yes, a join will accomplish what you want:
SELECT t1.*,
t2.flags
FROM table1 t1
JOIN table2 t2
ON t1.id = t2.id;
Note that JOIN is used here (rather than other types of joins such as LEFT JOIN) because JOIN will return only table1 records with a match in table2.id. LEFT JOIN, on the other hand, would return every table1 record, and table1 ids without a match in table2 would simply have null in the flags column of your returned table.
2) Select every field of records in table1 where the record's id is also found in either the id column of table2 or the flags column of table2. If that is the case, there are a few ways you could get the desired result, but achieving this using a subquery similar to the question
SELECT *
FROM table1
WHERE id IN (SELECT id FROM table2 UNION DISTINCT SELECT flags FROM table2)
You do this using join:
SELECT t1.*, t2.flags
FROM table1 t1 JOIN
table2 t2
ON t1.id = t2.id;
I want to delete an entry in a table where multiple fields match the results of another select subquery which takes data from another table.
query :
DELETE FROM table1
WHERE carriedby_circuit IN (SELECT
circuit_id
FROM table2
WHERE circuit_name IN (SELECT
t.sc_prod_service_id
FROM table3 t));
So I want to modify the query in such a way that if circuit_id form table2 is present in carriedBY_circuit or in CARRIED_CIRCUIT columns of table1. it should delete the row from table1.
You can try with merge:
merge into table1 t1
using (select t2.circuit_id from table2 t2 inner join table3 t3 on t2.circuit_name = t3.sc_prod_service_id) d
on (d.circuit_id = t1.carriedby_circuit or d.circuit_id = t1.carried_circuit)
when matched then delete;
Assuming you have 3 tables and you are working with ids. Table1, table2 and table3. Your best approach is to join table2 with table3. Then query its results, to delete from table1.
Example:
DELETE FROM table1
WHERE table1.id IN(SELECT distinct id FROM tabel1 UNION SELECT ID as id FROM tabel2);
PS: The union select will probably duplicate your Id´s, this is why I propose to use distinct.
I'm breaking my head here where I'm going wrong.
The following query:
SELECT SUM(table1.col1) FROM table1
returns value x.
And the following query:
SELECT SUM(table1.col1) FROM table2 RIGHT OUTER JOIN table1 ON table2.ID = table1.ID
returns value y. (I need the Join for the other data of table2). Why is the 2nd example returning a different value than in the first?
Make life easier on yourself, your colleagues that will support your code, and your clients by temporarily ignoring the existence of RIGHT OUTER JOIN. Use Table1 as the "from table" instead of table2.
Then, If aggregating, you will often find it necessary to do this BEFORE joining, so that the numbers are accurate. e.g.
SELECT T1.SUMCOL1
FROM (
SELECT id, SUM(col1) as SUMCOL1 FROM Table1 GROUP BY id
) T1
LEFT OUTER JOIN table2 T2 on T1.id = T2.ID
Obvious answer is because table2 is many to table1's one. That is, there are multiple rows in table2 for one id in table1. You may also be eliminating rows from table1 if the id isn't present in table2.
Compare:
SELECT COUNT(*) FROM table1
To:
SELECT COUNT(*) FROM table2 RIGHT OUTER JOIN table1 ON table2.ID = table1.ID
If you get different results, you're aggregating duplicates or eliminating rows from table1.
If you want to avoid this, you'll need to use a subquery.
I have two tables where each one contains columns with numbers. I need to compare columns in both tables and extract the number that does exist in first table, and does not exist in second one. I don't need unique value.
I wrote this query:
SELECT Table1.Numbers, Table1.Name
FROM Table1, Table2
WHERE Table1.Numbers != Table2.numbers
Since I am working on several million records can someone recommend more efficient query which would provide me with identical results?
I would use NOT EXISTS:
SELECT Table1.Numbers, Table1.Name
FROM Table1
WHERE NOT EXISTS(
SELECT 1 FROM Table2
WHERE Table1.Numbers=Table2.Numbers
)
Other approaches:
Should I use NOT IN, OUTER APPLY, LEFT OUTER JOIN, EXCEPT, or NOT EXISTS?
You can do this easily by checking for the existance on the number in Table2.
SELECT T1.Numbers
,T1.Name
FROM Table1 T1
WHERE NOT EXISTS (SELECT 1 FROM Table2 T2 WHERE T2.Numbers = T1.Numbers)
Try this (assuming that your Numbers column are not nullable)
SELECT T1.Numbers, T1.Name
FROM Table1 AS T1
LEFT JOIN Table2 AS T2 ON T1.Numbers = T2.Numbers
WHERE T2.Numbers IS NULL;
SELECT
Table1.Numbers, Table1.Name
FROM
Table1, Table2
GROUP BY
Table1, Table2
HAVING
COUNT(*) > 1
Sorry I missed and deleted earlier question on accident again.
I have a situation, I am trying to select distinct values from table 1 that are new and store them in table 2. The problem is that table has duplicates on column "name" but it does have a key column "id", but the different ids of course map to the same name.
My idea on the query would be
INSERT INTO TABLE2
(NAME, UniqueID)
SELECT DISTINCT TABLE1.NAME, TABLE1.ID
FROM TABLE1
LEFT JOIN TABLE2 ON TABLE1.ID=TABLE2.UniqueID
WHERE TABLE2.NAME IS NULL
Need help on getting the query to return my desired results, right now it still produces duplicates in table2 (on name column), which I don't want. I would want it to only append new records even if I run the query multiple times. For example if two new records were added into table1 but one has the name already in table 2, then the query would only add 1 new record to table2
just a note: I am using ms access, so it has strict syntax on single queries
EDIT:
Folliwing input I had came with this query
INSERT INTO TABLE2
(NAME, UniqueID)
SELECT TABLE1.NAME, Min(TABLE1.ID)
FROM TABLE1
LEFT JOIN TABLE2 ON TABLE1.NAME=TABLE2.NAME
WHERE TABLE2.UniqueID IS NULL
Group By TABLE1.NAME;
but these actually had to be separated to two separate wueries in access to run without a reserver error flag but now I ran into additional problem. When I run the two separate queries, it works fine the first time, but when I run it twice trying to test to see if any new records have been added to table 1, it then appends 1 record when no new records are in table 1, so it appends a blank name value and a duplicate unique id, and continually does that same process everytime I run it.
Since you're pulling both Name and ID, the distinct keyword will only pull distinct combinations of those. Two records with the same Name and different ID's is still valid.
In the case of two Names with different ID's, which would you like to be inserted?...
insert into table2 (Name, UniqueID)
select t1.Name, MIN(t1.ID)
from table1 t1
left join table2 t2 on t1.ID = t2.UniqueID
where t2.Name is null
group by t1.Name
in response to comments, I realize the Name field is what should be joined on, to prevent dupes that already exist.
insert into table2 (Name, UniqueID)
select t1.Name, MIN(t1.ID)
from table1 t1
left join table2 t2 on t1.Name = t2.Name
where t2.UniqueID is null
group by t1.Name
INSERT INTO TABLE2 (UniqueID, NAME)
SELECT min(t1.ID) as UniqueID, t1.NAME
FROM TABLE1 t1
LEFT JOIN TABLE2 t2 ON t1.ID=t2.UniqueID
WHERE t2.NAME IS NULL
group by t1.NAME