I have 2 queries. The first is what I want to accomplish, however, it was taking much too long. Here's how the query looked like:
SELECT *
FROM old_table
WHERE id NOT IN (SELECT id FROM new_table)
UNION ALL
SELECT *
FROM new_table
Basically, I want everything that's in the old table, but not in the new table. I then union everything from the old and new. Again, this query was taking much too long on a bigger dataset. So, I optimized it like so:
WITH union_tbl AS (
(SELECT * FROM old_table)
UNION ALL
(SELECT * FROM new_table)
), row_tbl AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY id ORDER BY ordering) AS row
FROM union_tbl
)
SELECT *
FROM row_tbl
WHERE row = 1
In the old_table and new_table (in a separate query) I add a new column to each called ordering. The new_table gets 1 for all its rows. For the old table, it gets 2 for all its rows. In the end, I select where the row number is 1. So that means if there's 2 rows one for new_table and one for old_table then it should get the new_table row instead.
This is how I'm envisioning it, however, I'm not getting the same results as my previous query. I'd expect it to have the same exact results with the same rows. What am I getting wrong? Is my query logic incorrect?
Can you try the below code?
SELECT a.*
FROM old_table a left join new_table b on a.id=b.id
WHERE b.id IS NULL
UNION ALL
SELECT *
FROM new_table
This is a very optimized way
Related
I want to get all rows in sequence from 2 tables in SQL Server.
Output should be 1st row from 1st table, then 1st row from 2nd table,
2nd row from 1st table, 2nd row from 2nd table....etc
What #eshirvana suggested will not get you the desired. Instead, it'll be table1.row1, table2.row1, table2.row2, table1.row2
You can use UNION to join data from two tables when the column names and types match. I'm making an assumption on how to order the data based on your desired outcome.
SELECT RowID, Row, z
FROM table1
UNION
SELECT *
FROM table2
ORDER BY z, RowID
Here's the working code:
https://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=068c0fd2056cc48718345e85b74b7bba
probably something like that :
select * from
(
select rowID,Row,z from table1
union all
select rowID,Row,z from table2
) alltables
order by z
You can try with below approach:
SELECT * FROM
(
SELECT RowId,Row,Z,1 AS TableOrder From Table1
UNION ALL
SELECT RowId,Row,z,2 AS TableOrder From Table2
)
ORDER BY Z,TableOrder
I have a table form which I need to extract some information. This table has an oracle spatial (MDSYS.SDO_GEOMETRY) column, from which I also need some data.
I started out with a simple query like this:
select id, field1, field2
FROM my_table;
After that, I was able to loop over the result to extract the data that was in the spatial column:
SELECT *
FROM TABLE (SELECT a.POSITIONMAP.sdo_ordinates
FROM my_table
WHERE ID = 18742084);
The POSITIONMAP.sdo_ordinates seems to usually hold 4 values, like these:
100050,887
407294,948
0,577464740471056
-0,816415625470689
I need the last 2 values. I can achieve that by changing the query into this:
SELECT * FROM
(SELECT rownum AS num,
column_value AS orientatie
FROM TABLE (SELECT a.POSITIONMAP.sdo_ordinates
FROM my_table
WHERE ID = 18742084))
WHERE num IN (3,4)
Looping over every row from my first query to extract the data from the POSITIONMAP column is of course not very performance friendly, so my query becomes slow very quickly.
I would like to retrieve all information in one query, but there are a few things that prevent me from doing so.
Not every row in the table has data in POSITIONMAP
Some rows do have data in POSITIONMAP, but they only contain 2 values (so not the 3rd and 4th value that I am looking for.
I need the data in one row for every row in the table (using the previous query would result in duplicate rows
The closest I got is:
select
id,
field1,
field2
t.*
FROM my_table v,
table (v.POSITIONMAP.sdo_ordinates) t
This gives my 4 rows for every row in my_table.
As soon as I try to put the rownum condition into this query, I get an error: "invalid user.table.column, table.column, or column specification"
Is there any way to combine what I want to do into 1 query?
You can use sdo_util.getvertices as follows:
select t.x,t.y
from my_table mt
,table(sdo_util.getvertices(mt.positionmap)) t
where t.id = 2
I'm assuming that your geometries are lines (gtype=2002) and points (gtype= 2001). If you want X,Y values for lines and empty values for point you can filter on the sdo_gtype property of the geometry object.
select t.x,t.y
from my_table mt
,table(sdo_util.getvertices(mt.positionmap)) t
where t.id = 2
and mt.positionmap.sdo_gtype=2002
union all
select null as X,
null as Y
from my_table mt
where mt.positionmap.sdo_gtype=2001
One method is to use the ROW_NUMBER() analytic function:
SELECT *
FROM (
select id,
field1,
field2,
t.*,
ROW_NUMBER() OVER ( PARTITION BY v.id ORDER BY ROWNUM ) AS rn
FROM my_table v,
TABLE( v.POSITIONMAP.sdo_ordinates ) t
)
WHERE rn IN ( 3, 4 )
I have the following problem.
Let TableA(Id int, Name nvarchar(200)) and TableB(Id int, Name nvarchar(200)).
If we run the following query:
SELECT *
FROM
(SELECT *
FROM TableA)
UNION
(SELECT *
FROM TableB)
we get the union of the two datasets.
My Problem is that I want the results of the second dataset to be the ordered by the Name column.
The reason why I need this, is the fact that TableA is a temporary table in my query, that always will hold one record, and this record I want to be the first in the resulting dataset from the union of the two datasets. Also, I want the multiple records of the TableB to be ordered by the Name column.
Unfortunately, when I try to execute the following query
SELECT *
FROM
(SELECT *
FROM TableA)
UNION
(SELECT *
FROM TableB
ORDER BY Name)
I get an ambiguous error message, that informs me that I have an incorrect syntax near the keyword order.
Thanks in advance for any help.
try this:
select id
, name
from
(select 1 as ordercol
, a.id
, a.name
from tableA
union
select 2 as ordercol
, b.id
, b.name
from tableB) i
order by ordercol, name
the error message resulted in you trying to union two subselects. you can put union between two selects that will then be put into a subselect. there is always a select after a union (or union all). i would also suggest you use a union all, that saves time because sql-server will otherwise try and remove records that are in both selects (which in this case is impossible due to the ordercol-column)
i have included a second order-by column that will order the first select before the second. if you order by that first and then by name, you should get the desired result.
I am trying to get the diff between two nearly identical tables in postgresql. The current query I am running is:
SELECT * FROM tableA EXCEPT SELECT * FROM tableB;
and
SELECT * FROM tableB EXCEPT SELECT * FROM tableA;
Each of the above queries takes about 2 minutes to run (Its a large table)
I wanted to combine the two queries in hopes to save time, so I tried:
SELECT * FROM tableA EXCEPT SELECT * FROM tableB
UNION
SELECT * FROM tableB EXCEPT SELECT * FROM tableA;
And while it works, it takes 20 minutes to run!!! I would guess that it would at most take 4 minutes, the amount of time to run each query individually.
Is there some extra work UNION is doing that is making it take so long? Or is there any way I can speed this up (with or without the UNION)?
UPDATE: Running the query with UNION ALL takes 15 minutes, almost 4 times as long as running each one on its own, Am I correct in saying that UNION (all) is not going to speed this up at all?
With regards to your "extra work" question. Yes. Union not only combines the two queries but also goes through and removes duplicates. It's the same as using a distinct statement.
For this reason, especially combined with your except statements "union all" would likely be faster.
Read more here:
http://www.postgresql.org/files/documentation/books/aw_pgsql/node80.html
In addition to combining the results of the first and second query, UNION by default also removes duplicate records. (see http://www.postgresql.org/docs/8.1/static/sql-select.html). The extra work involved in checking for duplicate records between the two queries is probably responsible for the extra time. In this situation there should not be any duplicate records so the extra work looking for duplicates can be avoided by specifying UNION ALL.
SELECT * FROM tableA EXCEPT SELECT * FROM tableB
UNION ALL
SELECT * FROM tableB EXCEPT SELECT * FROM tableA;
I don't think your code returns resultset you intend it to. I rather think you want to do this:
SELECT *
FROM (
SELECT * FROM tableA
EXCEPT
SELECT * FROM tableB
) AS T1
UNION
SELECT *
FROM (
SELECT * FROM tableB
EXCEPT
SELECT * FROM tableA
) AS T2;
In other words, you want the set of mutually exclusive members. If so, you need to read up on relational operator precedence in SQL ;) And when you have, you may realise the above can be rationalised to:
SELECT * FROM tableA
UNION
SELECT * FROM tableB
EXCEPT
SELECT * FROM tableA
INTERSECT
SELECT * FROM tableB;
FWIW, using subqueries (derived tables T1 and T2) to explicitly show (what would otherwise be implicit) relational operator precedence, your original query is this:
SELECT *
FROM (
SELECT *
FROM (
SELECT *
FROM tableA
EXCEPT
SELECT *
FROM tableB
) AS T2
UNION
SELECT *
FROM tableB
) AS T1
EXCEPT
SELECT *
FROM tableA;
The above can be relationalised to:
SELECT *
FROM tableB
EXCEPT
SELECT *
FROM tableA;
...and I think not what is intended.
You could use tableA FULL OUTER JOIN tableB, which would give what you want (with a propre join condition) with only 1 table scan, it probably would be faster than the 2 queries above.
Post more info please.
For this MySQL SELECT statement:
SELECT * FROM MY_TABLE WHERE ID IN(x,y,y,z):
I want 4 rows back - ie I WANT row duplication for the case where I pass duplicate IDs in the list.
Is this possible?
using the IN() construct, that's not possible.
the only way i can think to do this is with a UNION:
SELECT * FROM my_table WHERE id = x
UNION ALL
SELECT * FROM my_table WHERE id = y
UNION ALL
SELECT * FROM my_table WHERE id = y
UNION ALL
SELECT * FROM my_table WHERE id = z
but in all honesty, i would just do the IN() like you have it and make your app code duplicate the rows as needed.
Put your IDs, including dups in a temp table and join your results on that table. The join will take care of filtering, but will keep duplicates if it's in the temp table twice
SELECT * FROM MY_TABLE WHERE ID IN(x,y,z)
union all
SELECT * FROM MY_TABLE WHERE ID IN(y)
To me, IN specify a set of values to search in (and duplication is a concept that conflict with the set one).
You should use other mean to reach your scope.