I think I have a misunderstanding of how NOT EXISTS work and hope it can be clarified to me.
Here is the sample code I am running (also on SQL Fiddle)
select sum(col1) col1, sum(col2) col1, sum(col3) col3
from (
select 1 col1, 1 col2, 1 col3
from dual tbl1
)
where not exists(
select 2 col1, 1 col2, 1 col3
from dual tbl2
)
I thought that it should return:
1, 1, 1
But instead it returns nothing.
I make this assumption only on the fact that I though NOT EXISTS would give me a list of all the rows in the first query that do not exist in the second query (in this case 1,1,1)
Why does this not work
What would be the appropriate way to make it work the way I am expecting it to?
You are performing an uncorrelated subquery in your NOT EXISTS() condition. It always returns exactly one row, therefore the NOT EXISTS condition is never satisfied, and your query returns zero rows.
Oracle has a rowset difference operator, MINUS, that should do what you wanted:
select sum(col1) col1, sum(col2) col1, sum(col3) col3
from (
select 1 col1, 1 col2, 1 col3
from dual tbl1
MINUS
select 2 col1, 1 col2, 1 col3
from dual tbl2
)
SQL Server has an EXCEPT operator that does the same thing as Oracle's MINUS. Some other databases implement one or the other of these.
EXISTS just returns true if a record exists in the result set; it does not do any value checking. Since the sub-query returns one record, EXISTS is true, NOT EXISTS is false, and you get no records in your result.
Typically you have a WHERE cluase in the sub-query to compare values to the outer query.
One way to accomplish what you want is to use EXCEPT:
select sum(col1) col1, sum(col2) col1, sum(col3) col3
from (
select 1 col1, 1 col2, 1 col3
from dual tbl1
)
EXCEPT(
select 2 col1, 1 col2, 1 col3
from dual tbl2
)
A not exists that includes a select from dual will never return anything. Not exists will exclude rows where the embedded SQL returns something. Normally not exists should be used more like this:
select ... from MY_TABLE A where not exists (select 1 from OTHER_TABLE B where A.SOME_COL = B.SOME_COL)
As using NOT EXISTS is not good approach as it is return only single row so try it with MINUS or EXCEPT
select sum(col1) col1, sum(col2) col1, sum(col3) col3 from ( select 1 col1, 1 col2, 1 col3 from dual tbl1 MINUS select 2 col1, 1 col2, 1 col3 from dual tbl2 )
select sum(col1) col1, sum(col2) col1, sum(col3) col3 from ( select 1 col1, 1 col2, 1 col3 from dual tbl1 ) EXCEPT( select 2 col1, 1 col2, 1 col3 from dual tbl2 )
Related
The problem is:
select (..)
UNION
select (..)
Result is:
Col1, Col2, Col3
Val1 Text1 Data
Val1 Text2 Data
The problem is that i need to save only 1 row of this two. Col2 value is not same at fact, but the same in business logic.
So, how to get result like this:
Col1, Col2,Col3
Val1 Text1 Data
OR
Col1, Col2, Col3
Val1 Text2 Data
Thank you!
You can place the UNION in a subquery and group again
SELECT
Col1,
MIN(Col2),
Col3
FROM (
SELECT Col1, Col2, Col3
FROM table1 t1
UNION ALL
SELECT Col1, Col2, Col3
FROM table2 t2
) t
GROUP BY
Col1,
Col2;
Note the use of UNION ALL rather than UNION, because you are grouping anyway it is not necessary to de-duplicate first.
Hmmm . . . If you want one row per val, then one method is:
with t1 as ( < query 1 here > ),
t2 as ( < query 2 here > )
select t1.*
from t1
union all
select t2.*
from t2
where not exists (select 1 from t1 where t1.val = t2.val);
I'm trying to union two tables but I need to essentially 'prefer' the first table using just one 'id' column.
If an 'id' appears in the second table that already exists in the first, I do not want to include that record.
Query looks like this
select id, col2, col3
from table(p_package.getData(param))
union
select id, col2, col3
from table1
where col7 = 'pass'
and col8 <> 'A'
and col9 = to_date(Date, 'mm/dd/yyyy')
the p_package.getData(param) is a pipelined function which returns a table. I would like to avoid calling this twice for performance reasons
You can use the ROW_NUMBER() analytic function to remove the duplicates:
SELECT id, col2, col3
FROM (
SELECT id, col2, col3,
ROW_NUMBER() OVER ( PARTITION BY id ORDER BY priority ) AS rn
FROM (
select id, col2, col3, 1 AS priority
from table(p_package.getData(param))
UNION ALL
select id, col2, col3, 2
from table1
where col7 = 'pass'
and col8 <> 'A'
and col9 = to_date(Date, 'mm/dd/yyyy')
)
)
WHERE rn = 1
and as a bonus, since you're filtering the duplicates elsewhere, you could change UNION to UNION ALL.
If you can have duplicates id values from the pipelined function and you want those but not any from table1 then:
SELECT id, col2, col3
FROM (
SELECT id, col2, col3, priority
ROW_NUMBER() OVER ( PARTITION BY id ORDER BY priority ) AS rn
FROM (
select id, col2, col3, 1 AS priority
from table(p_package.getData(param))
UNION ALL
select id, col2, col3, 2
from table1
where col7 = 'pass'
and col8 <> 'A'
and col9 = to_date(Date, 'mm/dd/yyyy')
)
)
WHERE priority = 1
OR rn = 1
Assuming you don't want to include any col1 value in the second half of the union which would introduce a value already included in the first half, you could use an exists clause:
select col1, col2, col3
from table(p_package.getData(param))
union
select col1, col2, col3
from table1 t1
where col7 = 'pass' and col8 <> 'A'and col9 = to_date(Date, 'mm/dd/yyyy') and
not exists (select 1 from table(p_package.getData(param)) t2
where t1.col1 = t2.col1);
The other solutions work but I opted to use a common table expression as suggested by xQbert
with cte as
(select id, col2, col3
from table(p_package.getData(param)))
select * from cte
union
select id, col2, col3
from table1
where col7 = 'pass'
and col8 <> 'A'
and col9 = to_date(Date, 'mm/dd/yyyy')
and id not in (select id from cte)
EDIT: I realized that a CTE does not actually store the data returned by a query but stores the query itself instead. While this works it does not avoid calling the pipelined function twice
I am currently using UNION on two queries (see psuedo-code below):
query1
UNION
query2
I want to add an additional column to my results that says the source of the data. The new column called "Source" would return one of the following: "1", "2", or "both".
Being able to handle "both" is very important because query1 and query2 will have similar results and many overlapping records. If anyone could help point me in the right direction, especially with how to handle the "both" case, that would be greatly appreciated!
Sample:
If query1 has a row "Apple,Yellow,Bob" and query2 has the same row, then the result I'm hoping for is:
"Apple,Yellow,Bob,Both"
The individual queries themselves will not have duplicates, but there may be the same row both in query1 and query2 (as seen above).
you can make use of an additional column col4 like this
select col1,col2,col3,sum(col4)
from(
Select col1, col2, col3, 1 as col4 from table1
UNION
Select col1,col2,col3, 2 as col4 from table4
)
group by col1,col2,col3
The records with col4=1 only exist in table1.
The records with col4=2 only exist in table2.
The records with col4=3 exist in both table1+table
add a Source field to both query 1 and query 2:
select 1 as source, ...
from table1
union
select 2 as source, ...
from table2
Here's one way
WITH T
AS (SELECT '1' AS Source,
Col1,
Col2,
Col3
FROM table1
UNION ALL
SELECT '2' AS Source,
Col1,
Col2,
Col3
FROM table2)
SELECT CASE
WHEN MAX(Source) = MIN(Source) THEN Source
ELSE 'Both'
END AS Source,
Col1,
Col2,
Col3
FROM T
GROUP BY Col1,
Col2,
Col3
One more approach
SELECT col1
,col2
,source = CASE
WHEN count(DISTINCT source) > 1
THEN 'Both'
ELSE max(source)
END
FROM (
SELECT col1 ,col2, source = 'source1'
FROM source1
UNION ALL
SELECT col1, col2, source = 'source2'
FROM source2
) u
GROUP BY col1, col2
You can try this
SELECT
a.col1 , a.col2,
CASE WHEN MAX(a.Source) <> MIN(a.Source)
THEN 'BOTH'
ELSE MAX(a.Source) END
FROM
(
SELECT
col1, col2 ,'Source2' AS Source
FROM Table1
UNION ALL
SELECT
col1, col2 ,'Source1' AS Source
FROM Table2
) a
GROUP BY
a.col1 , a.col2
Link to the Sample
I'm trying to write a query that pulls data from a lot of tables, and has about 20 unions. It's pulling the same information repeatedly, but with more layers each time, to show a sort of tree.
I want to compare the final two columns. I'm using a case to do this, and if I add a case to this query then I get the error "query block has incorrect number of results columns". This seems to be because the final select in the union has an extra column (the compare case).
Is there any way to work around this? I don't want to add the case to each select, as this would add about 15 more columns that I don't want.
Use a sub-query:
SELECT col1,
col2,
CASE
WHEN col1 = 'somevalue'
THEN 'someresult'
ELSE 'otherresult'
END AS col3
FROM (
SELECT col1, col2 FROM table1 UNION ALL
SELECT col1, col2 FROM table2 UNION ALL
SELECT col1, col2 FROM table3
-- ...
);
Or use a sub-query factoring clause:
WITH data ( col1, col2 ) AS (
SELECT col1, col2 FROM table1 UNION ALL
SELECT col1, col2 FROM table2 UNION ALL
SELECT col1, col2 FROM table3
-- ...
)
SELECT col1,
col2,
CASE
WHEN col1 = 'somevalue'
THEN 'someresult'
ELSE 'otherresult'
END AS col3
FROM data;
I am trying to combine three tables in an SQLite database into one new combined table. The three tables have the same column names, but the third table is missing one of the columns. Here is how I am trying to do it:
CREATE TABLE cobmined
AS
SELECT col1, col2, col3
FROM
(
SELECT col1, col2, col3 from table1
UNION ALL
SELECT col1, col2, col3 from table2
UNION ALL
SELECT col1, col2 from table3
) s
;
This works when doing this only on the first two tables, when adding the third table I get the message:
SELECTs to the left and right of UNION do not have the same number of result columns
Is there a way to let SQL ignore the missing column and leave it with NULLs if needed?
Add a NULL value to the third table
CREATE TABLE cobmined
AS
SELECT col1, col2, col3
FROM
(
SELECT col1, col2, col3 from table1
UNION ALL
SELECT col1, col2, col3 from table2
UNION ALL
SELECT col1, col2, null from table3
) s
;
Also, no need for sub-query
CREATE TABLE cobmined
AS
SELECT col1, col2, col3 from table1
UNION ALL
SELECT col1, col2, col3 from table2
UNION ALL
SELECT col1, col2, null from table3
I want to note that you don't need the subquery:
CREATE TABLE combined AS
SELECT col1, col2, col3 from table1
UNION ALL
SELECT col1, col2, col3 from table2
UNION ALL
SELECT col1, col2, NULL from table3;
In addition, you may find that a view is more suitable for your purposes than an actual table.