I have a select that look like this:
SELECT * FROM (SELECT DISTICT COL1, COL2, COL3
FROM view a WHERE conditions ....
) QUERY
WHERE CONDITIONS... LIMIT 20 OFFSET 0
I'm executing this from java and I need this query return an unique id.
So i try:
SELECT TRIM(CHAR(HEX(GENERATE_UNIQUE()))) AS GUID, QUERY.* FROM (SELECT DISTICT COL1, COL2, COL3
FROM view a WHERE conditions ....
) QUERY
WHERE CONDITIONS... LIMIT 20 OFFSET 0
This one return an error telling me I can't use this function in that place.
If i try:
SELECT * FROM (SELECT DISTINCT TRIM(CHAR(HEX(GENERATE_UNIQUE()))) AS GUID, COL1, COL2, COL3
FROM view a WHERE conditions ....
) QUERY
WHERE CONDITIONS... LIMIT 20 OFFSET 0
I have duplicated rows because it is like I execute query wihout DISTINCT
Does anyone know a way to do it?
I don't know DB2 version (I have tried all solutions from How to check db2 version )
If a numeric id would do, how about just using row_number():
SELECT CAST(ROW_NUMBER() OVER (ORDER BY COL1, COL2, COL3) as VARCHAR(255)) as unique_id,
QUERY.*
FROM (SELECT DISTICT COL1, COL2, COL3
FROM view a
WHERE conditions ....
) QUERY
WHERE CONDITIONS...
LIMIT 20 OFFSET 0
Related
I want to select everything from mytable1 and combine that with just as many rows from mytable2. In my case mytable1 always has fewer rows than mytable2 and I want the final table to be a 50-50 mix of data from each table. While I feel like the following code expresses what I want logically, it doesn't work syntax wise:
Syntax error: Expected "#" or integer literal or keyword CAST but got
"(" at [3:1]
(SELECT * FROM `mytable1`)
UNION ALL (
SELECT * FROM `mytable2`
LIMIT (SELECT COUNT(*) FROM`mytable1`)
)
Using standard SQL in bigquery
The docs state that LIMIT clause accept only literal or parameter values. I think you can ROW_NUMBER() the rows from second table and limit based on that:
SELECT col1, col2, col3
FROM mytable1
UNION ALL
SELECT col1, col2, col3
FROM (
SELECT col1, col2, col3, ROW_NUMBER() OVER () AS rn
FROM mytable2
) AS x
WHERE x.rn <= (SELECT COUNT(*) FROM mytable1)
Each SELECT statement within UNION must have the same number of
columns
The columns must also have similar data types
The columns in each SELECT statement must also be in the same order
As your mytable1 always less column than mytable2 so you have to put same number of column by selection
select col1,col2,col3,'' as col4 from mytable1 --in case less column you can use alias
union all
select col1,col2,col3,col4 from mytable2
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 looking for a query where I can get unique values(5) in a table. For example.
The table consists of more 100+ columns. Is there any way I can get unique values.
I am using google big query and tried this option
select col1 col2 ... coln
from tablename
where col1 is not null and col2 is not null
group by col1,col2... coln
order by col1, col2... coln
limit 5
But problem is it gives zero records if all the column are null
Thanks
R
I think you might be able to do this in Google bigquery, assuming that the types for the columns are compatible:
select colname, colval
from (select 'col1' as colname, col1 as colvalue
from t
where col1 is not null
group by col1
limit 5
),
(select 'col2' as colname, col2 as colvalue
from t
where col2 is not null
group by col2
limit 5
),
. . .
For those not familiar with the syntax, a comas in the from clause means union all, not cross join in this dialect. Why did they have to change this?
Try This one, i hope it works
;With CTE as (
select * ,ROW_NUMBER () over (partition by isnull(col1,''),isnull(col2,'')... isnull(coln,'') order by isnull(col1,'')) row_id
from tablename
) select * from CTE where row_id =1
Experts, I have a single table with multiple columns. col1, col2, col3, col4, col5, col6
I need to select distinct (col4), but I need all other columns also on my output.
If I run, this ( select distinct(col4 ) from table1 ), then I get only col4 on my output.
May I know, how to do it on db2?.
Thank you
You simply do this...
Select * From Table1 Where col4 In (Select Distinct(col4) From Table1)
I'm not sure if you will be able to do this.
You might try to run group by on this column. You will be able to run some aggregate functions on other columns.
select count(col1), col4 from table1 group by (col4);
none of the answers worked for me so here is one that i got working. use group by on col4 while taking max values of other columns
select max(col1) as col1,max(col2) as col2,max(col3) as col3
, col4
from
table1
group by col4
At least in DB2, you can execute
SELECT
DISTINCT *
FROM
<YOUR TABLE>
Which will give you every distinct combination of your (in this case) 6 columns.
Otherwise, you'll have to specify what columns you want to include. If you do that, you can either use select distinct or group by.
This is my view:
Create View [MyView] as
(
Select col1, col2, col3 From Table1
UnionAll
Select col1, col2, col3 From Table2
)
I need to add a new column named Id and I need to this column be unique so I think to add new column as identity. I must mention this view returned a large of data so I need a way with good performance, And also I use two select query with union all I think this might be some complicated so what is your suggestion?
Use the ROW_NUMBER() function in SQL Server 2008.
Create View [MyView] as
SELECT ROW_NUMBER() OVER( ORDER BY col1 ) AS id, col1, col2, col3
FROM(
Select col1, col2, col3 From Table1
Union All
Select col1, col2, col3 From Table2 ) AS MyResults
GO
The view is just a stored query that does not contain the data itself so you can add a stable ID. If you need an id for other purposes like paging for example, you can do something like this:
create view MyView as
(
select row_number() over ( order by col1) as ID, col1 from (
Select col1 From Table1
Union All
Select col1 From Table2
) a
)
There is no guarantee that the rows returned by a query using ROW_NUMBER() will be ordered exactly the same with each execution unless the following conditions are true:
Values of the partitioned column are unique. [partitions are parent-child, like a boss has 3 employees][ignore]
Values of the ORDER BY columns are unique. [if column 1 is unique, row_number should be stable]
Combinations of values of the partition column and ORDER BY columns are unique. [if you need 10 columns in your order by to get unique... go for it to make row_number stable]"
There is a secondary issue here, with this being a view. Order By's don't always work in views (long-time sql bug). Ignoring the row_number() for a second:
create view MyView as
(
select top 10000000 [or top 99.9999999 Percent] col1
from (
Select col1 From Table1
Union All
Select col1 From Table2
) a order by col1
)
Using "row_number() over ( order by col1) as ID" is very expensive.
This way is much more efficient in cost:
Create View [MyView] as
(
Select ID = isnull(cast(newid() as varchar(40)), '')
, col1
, col2
, col3
From Table1
UnionAll
Select ID = isnull(cast(newid() as varchar(40)), '')
, col1
, col2
, col3
From Table2
)
use ROW_NUMBER() with "order by (select null)" this will be less expensive and will get your result.
Create View [MyView] as
SELECT ROW_NUMBER() over (order by (select null)) as id, *
FROM(
Select col1, col2, col3 From Table1
Union All
Select col1, col2, col3 From Table2 ) R
GO