Say I have an table like this:
DROP TABLE tmp;
CREATE TABLE tmp (id SERIAL, name TEXT);
INSERT INTO tmp VALUES (1, 'one'), (2, 'two'), (3, 'three'), (4, 'four'), (5, 'five');
SELECT id, name FROM tmp;
It's like this:
id | name
----+-------
1 | one
2 | two
3 | three
4 | four
5 | five
(5 rows)
Then I have an array of ARRAY[3,1,2]. I want to get query the table by this array, so I can get an array of ARRAY['three', 'one', 'two']. I think this should be very easy but I just can't get it figured out.
Thanks in advance.
To preserve the array order, it needs to be unnested with the index order (using row_number()), then joined to the tmp table:
SELECT array_agg(name ORDER BY f.ord)
FROM (
select row_number() over() as ord, a
FROM unnest(ARRAY[3, 1, 2]) AS a
) AS f
JOIN tmp ON tmp.id = f.a;
array_agg
-----------------
{three,one,two}
(1 row)
Use unnest function:
SELECT id, name FROM tmp
WHERE id IN (SELECT unnest(your_array));
There is a different technique as suggested by Eelke:
You can also use the any operator
SELECT id, name FROM tmp WHERE id = ANY ARRAY[3, 1, 2];
If you want to return the array as output then try this:
SELECT array_agg(name) FROM tmp WHERE id = ANY (ARRAY[3, 1, 2]);
SQL FIDDLE
Related
If my subquery foo liberates the rows:-
ID, USERS
1 {23129}
2 {23142}
3 {23300,23300}
4 {23129,23300}
How can I get a count of unique users in a query using a window function such as:-
SELECT ... FROM ( <subquery> ) FOO
I tried this:-
array_length(array_agg(array_length(array(SELECT Distinct unnest(users))),1)) over(), 1)
But get the error that the array dimensions are not the same
NOTE WELL: I cannot change the subquery to solve this problem.
I can get the IDs in an array as follows:-
string_to_array(string_agg(array_to_string(user_ids, ','), ',') over(),',')
But they are not distinct.
You're overcomplicating things - you can unnest the array, and then query a distinct count from it:
SELECT COUNT(DISTINCT u)
FROM (SELECT UNNEST(users) AS u
FROM mytable) t
You can always use a known alghoritm in a simple SQL function:
create or replace function array_unique_elements(arr anyarray)
returns integer
language sql immutable
as $$
select count(distinct a)::int
from unnest(arr) a
$$;
Use:
select *, array_unique_elements(users)
from (
values
(1, '{23129}'::int[]),
(2, '{23142}'),
(3, '{23300,23300}'),
(4, '{23129,23300}')
) foo (id, users)
id | users | array_unique_elements
----+---------------+-----------------------
1 | {23129} | 1
2 | {23142} | 1
3 | {23300,23300} | 1
4 | {23129,23300} | 2
(4 rows)
I would as well just count distinct as Mureinik suggests.
And regarding error that you get - here's tight syntax example with array_length:
t=# with a(v) as (values('{1,2}'::int[]),('{2,3}'))
select array_length(array_agg(distinct unnest),1) from (
select unnest(v) from a
) a;
array_length
--------------
3
(1 row)
Of course it WILL NOT with window aggregation - only with GROUP BY
Is there a built in function for comma separated column values in DB2 SQL?
Example: If there are columns with an ID and it has 3 rows with the same ID but have three different roles, the data should be concatenated with a comma.
ID | Role
------------
4555 | 2
4555 | 3
4555 | 4
The output should look like the following, per row:
4555 2,3,4
LISTAGG function is new function in DB2 LUW 9.7
see example:
create table myTable (id int, category int);
insert into myTable values (1, 1);
insert into myTable values (2, 2);
insert into myTable values (5, 1);
insert into myTable values (3, 1);
insert into myTable values (4, 2);
example: select without any order in grouped column
select category, LISTAGG(id, ', ') as ids from myTable group by category;
result:
CATEGORY IDS
--------- -----
1 1, 5, 3
2 2, 4
example: select with order by clause in grouped column
select
category,
LISTAGG(id, ', ') WITHIN GROUP(ORDER BY id ASC) as ids
from myTable
group by category;
result:
CATEGORY IDS
--------- -----
1 1, 3, 5
2 2, 4
I think with this smaller query, you can do what you want.
This is equivalent of MySQL's GROUP_CONCAT in DB2.
SELECT
NUM,
SUBSTR(xmlserialize(xmlagg(xmltext(CONCAT( ', ',ROLES))) as VARCHAR(1024)), 3) as ROLES
FROM mytable
GROUP BY NUM;
This will output something like:
NUM ROLES
---- -------------
1 111, 333, 555
2 222, 444
assumming your original result was something like that:
NUM ROLES
---- ---------
1 111
2 222
1 333
2 444
1 555
Depending of the DB2 version you have, you can use XML functions to achieve this.
Example table with some data
create table myTable (id int, category int);
insert into myTable values (1, 1);
insert into myTable values (2, 2);
insert into myTable values (3, 1);
insert into myTable values (4, 2);
insert into myTable values (5, 1);
Aggregate results using xml functions
select category,
xmlserialize(XMLAGG(XMLELEMENT(NAME "x", id) ) as varchar(1000)) as ids
from myTable
group by category;
results:
CATEGORY IDS
-------- ------------------------
1 <x>1</x><x>3</x><x>5</x>
2 <x>2</x><x>4</x>
Use replace to make the result look better
select category,
replace(
replace(
replace(
xmlserialize(XMLAGG(XMLELEMENT(NAME "x", id) ) as varchar(1000))
, '</x><x>', ',')
, '<x>', '')
, '</x>', '') as ids
from myTable
group by category;
Cleaned result
CATEGORY IDS
-------- -----
1 1,3,5
2 2,4
Just saw a better solution using XMLTEXT instead of XMLELEMENT here.
Since DB2 9.7.5 there is a function for that:
LISTAGG(colname, separator)
check this for more information: Using LISTAGG to Turn Rows of Data into a Comma Separated List
My problem was to transpose row fields(CLOB) to column(VARCHAR) with a CSV and use the transposed table for reporting. Because transposing on report layer slows down the report.
One way to go is to use recursive SQL. You can find many articles about that but its difficult and resource consuming if you want to join all your recursive transposed columns.
I created multiple global temp tables where I stored single transposed columns with one key identifier. Eventually, I had 6 temp tables for joining 6 columns but due to limited resource allocation I wasnt able to bring all columns together. I opted to below 3 formulas and then I just had to run 1 query which gave me output in 10 seconds.
I found various articles on using XML2CLOB functions and have found 3 different ways.
REPLACE(VARCHAR(XML2CLOB(XMLAGG(XMLELEMENT(NAME "A",ALIASNAME.ATTRIBUTENAME)))),'', ',') AS TRANSPOSED_OUTPUT
NVL(TRIM(',' FROM REPLACE(REPLACE(REPLACE(CAST(XML2CLOB(XMLAGG(XMLELEMENT(NAME "E", ALIASNAME.ATTRIBUTENAME))) AS VARCHAR(100)),'',' '),'',','), '', 'Nothing')), 'Nothing') as TRANSPOSED_OUTPUT
RTRIM(REPLACE(REPLACE(REPLACE(VARCHAR(XMLSERIALIZE(XMLAGG(XMLELEMENT(NAME "A",ALIASNAME.ATTRIBUTENAME) ORDER BY ALIASNAME.ATTRIBUTENAME) AS CLOB)), '',','),'',''),'','')) AS TRANSPOSED_OUTPUT
Make sure you are casting your "ATTRIBUTENAME" to varchar in a subquery and then calling it here.
other possibility, with recursive cte
with tablewithrank as (
select id, category, rownumber() over(partition by category order by id) as rangid , (select count(*) from myTable f2 where f1.category=f2.category) nbidbycategory
from myTable f1
),
cte (id, category, rangid, nbidbycategory, rangconcat) as (
select id, category, rangid, nbidbycategory, cast(id as varchar(500)) from tablewithrank where rangid=1
union all
select f2.id, f2.category, f2.rangid, f2.nbidbycategory, cast(f1.rangconcat as varchar(500)) || ',' || cast(f2.id as varchar(500)) from cte f1 inner join tablewithrank f2 on f1.rangid=f2.rangid -1 and f1.category=f2.category
)
select category, rangconcat as IDS from cte
where rangid=nbidbycategory
Try this:
SELECT GROUP_CONCAT( field1, field2, field3 ,field4 SEPARATOR ', ')
Ideally I'd like to run a single query that returns a table where each row is a column name of a specified table, and jsonb array of all the distinct values in the table corresponding to that column.
The tricky part seems to be doing so dynamically, where I can specify just the table and not each individual column.
I can retrieve all the column names of the relevant table from information_schema.columns, but is there an easy way to couple this with a query to retrieve all the distinct values for each column?
create table example(id int primary key, str text, val numeric);
insert into example values
(1, 'a', 1),
(2, 'a', 2),
(3, 'b', 2);
select key, array_agg(distinct value)
from example, jsonb_each_text(to_jsonb(example))
group by key;
key | array_agg
-----+-----------
id | {1,2,3}
str | {a,b}
val | {1,2}
(3 rows)
or
select key, json_agg(distinct value)
from example, jsonb_each(to_jsonb(example))
group by key;
key | json_agg
-----+------------
id | [1, 2, 3]
str | ["a", "b"]
val | [1, 2]
(3 rows)
No sure I understood you completely, but this seems to do what you want:
select json_build_object(colname, array_agg(distinct val))
from the_table
cross join lateral json_each_text(row_to_json(the_table)) as j(colname,val)
group by colname;
I have a table where one column has an array - but stored in a text format:
mytable
id ids
-- -------
1 '[3,4]'
2 '[3,5]'
3 '[3]'
etc ...
I want to find all records that have the value 5 as an array element in the ids column.
I was trying to achieve this by using the "string to array" function and removing the [ symbols with the translate function, but couldn't find a way.
You can do this: http://www.sqlfiddle.com/#!1/5c148/12
select *
from tbl
where translate(ids, '[]','{}')::int[] && array[5];
Output:
| ID | IDS |
--------------
| 2 | [3,5] |
You can also use bool_or: http://www.sqlfiddle.com/#!1/5c148/11
with a as
(
select id, unnest(translate(ids, '[]','{}')::int[]) as elem
from tbl
)
select id
from a
group by id
having bool_or(elem = 5);
To see the original elements:
with a as
(
select id, unnest(translate(ids, '[]','{}')::int[]) as elem
from tbl
)
select id, '[' || array_to_string(array_agg(elem), ',') || ']' as ids
from a
group by id
having bool_or(elem = 5);
Output:
| ID | IDS |
--------------
| 2 | [3,5] |
Postgresql DDL is atomic, if it's not late yet in your project, just structure your stringly-typed array to a real array: http://www.sqlfiddle.com/#!1/6e18c/2
alter table tbl
add column id_array int[];
update tbl set id_array = translate(ids,'[]','{}')::int[];
alter table tbl drop column ids;
Query:
select *
from tbl
where id_array && array[5]
Output:
| ID | ID_ARRAY |
-----------------
| 2 | 3,5 |
You can also use contains operator: http://www.sqlfiddle.com/#!1/6e18c/6
select *
from tbl
where id_array #> array[5];
I prefer the && syntax though, it directly connotes intersection. It reflects that you are detecting if there's an intersection between two sets(array is a set)
http://www.postgresql.org/docs/8.2/static/functions-array.html
If you store the string representation of your arrays slightly differently, you can cast to array of integer directly:
INSERT INTO mytable
VALUES
(1, '{3,4}')
,(2, '{3,5}')
,(3, '{3}');
SELECT id, ids::int[]
FROM mytable;
Else, you have to put in one more step:
SELECT (translate(ids, '[]','{}'))::int[]
FROM mytable
I would consider making the column an array type to begin with.
Either way, you can find your row like this:
SELECT id, ids
FROM (
SELECT id, ids, unnest(ids::int[]) AS elem
FROM mytable
) x
WHERE elem = 5
Is there a built in function for comma separated column values in DB2 SQL?
Example: If there are columns with an ID and it has 3 rows with the same ID but have three different roles, the data should be concatenated with a comma.
ID | Role
------------
4555 | 2
4555 | 3
4555 | 4
The output should look like the following, per row:
4555 2,3,4
LISTAGG function is new function in DB2 LUW 9.7
see example:
create table myTable (id int, category int);
insert into myTable values (1, 1);
insert into myTable values (2, 2);
insert into myTable values (5, 1);
insert into myTable values (3, 1);
insert into myTable values (4, 2);
example: select without any order in grouped column
select category, LISTAGG(id, ', ') as ids from myTable group by category;
result:
CATEGORY IDS
--------- -----
1 1, 5, 3
2 2, 4
example: select with order by clause in grouped column
select
category,
LISTAGG(id, ', ') WITHIN GROUP(ORDER BY id ASC) as ids
from myTable
group by category;
result:
CATEGORY IDS
--------- -----
1 1, 3, 5
2 2, 4
I think with this smaller query, you can do what you want.
This is equivalent of MySQL's GROUP_CONCAT in DB2.
SELECT
NUM,
SUBSTR(xmlserialize(xmlagg(xmltext(CONCAT( ', ',ROLES))) as VARCHAR(1024)), 3) as ROLES
FROM mytable
GROUP BY NUM;
This will output something like:
NUM ROLES
---- -------------
1 111, 333, 555
2 222, 444
assumming your original result was something like that:
NUM ROLES
---- ---------
1 111
2 222
1 333
2 444
1 555
Depending of the DB2 version you have, you can use XML functions to achieve this.
Example table with some data
create table myTable (id int, category int);
insert into myTable values (1, 1);
insert into myTable values (2, 2);
insert into myTable values (3, 1);
insert into myTable values (4, 2);
insert into myTable values (5, 1);
Aggregate results using xml functions
select category,
xmlserialize(XMLAGG(XMLELEMENT(NAME "x", id) ) as varchar(1000)) as ids
from myTable
group by category;
results:
CATEGORY IDS
-------- ------------------------
1 <x>1</x><x>3</x><x>5</x>
2 <x>2</x><x>4</x>
Use replace to make the result look better
select category,
replace(
replace(
replace(
xmlserialize(XMLAGG(XMLELEMENT(NAME "x", id) ) as varchar(1000))
, '</x><x>', ',')
, '<x>', '')
, '</x>', '') as ids
from myTable
group by category;
Cleaned result
CATEGORY IDS
-------- -----
1 1,3,5
2 2,4
Just saw a better solution using XMLTEXT instead of XMLELEMENT here.
Since DB2 9.7.5 there is a function for that:
LISTAGG(colname, separator)
check this for more information: Using LISTAGG to Turn Rows of Data into a Comma Separated List
My problem was to transpose row fields(CLOB) to column(VARCHAR) with a CSV and use the transposed table for reporting. Because transposing on report layer slows down the report.
One way to go is to use recursive SQL. You can find many articles about that but its difficult and resource consuming if you want to join all your recursive transposed columns.
I created multiple global temp tables where I stored single transposed columns with one key identifier. Eventually, I had 6 temp tables for joining 6 columns but due to limited resource allocation I wasnt able to bring all columns together. I opted to below 3 formulas and then I just had to run 1 query which gave me output in 10 seconds.
I found various articles on using XML2CLOB functions and have found 3 different ways.
REPLACE(VARCHAR(XML2CLOB(XMLAGG(XMLELEMENT(NAME "A",ALIASNAME.ATTRIBUTENAME)))),'', ',') AS TRANSPOSED_OUTPUT
NVL(TRIM(',' FROM REPLACE(REPLACE(REPLACE(CAST(XML2CLOB(XMLAGG(XMLELEMENT(NAME "E", ALIASNAME.ATTRIBUTENAME))) AS VARCHAR(100)),'',' '),'',','), '', 'Nothing')), 'Nothing') as TRANSPOSED_OUTPUT
RTRIM(REPLACE(REPLACE(REPLACE(VARCHAR(XMLSERIALIZE(XMLAGG(XMLELEMENT(NAME "A",ALIASNAME.ATTRIBUTENAME) ORDER BY ALIASNAME.ATTRIBUTENAME) AS CLOB)), '',','),'',''),'','')) AS TRANSPOSED_OUTPUT
Make sure you are casting your "ATTRIBUTENAME" to varchar in a subquery and then calling it here.
other possibility, with recursive cte
with tablewithrank as (
select id, category, rownumber() over(partition by category order by id) as rangid , (select count(*) from myTable f2 where f1.category=f2.category) nbidbycategory
from myTable f1
),
cte (id, category, rangid, nbidbycategory, rangconcat) as (
select id, category, rangid, nbidbycategory, cast(id as varchar(500)) from tablewithrank where rangid=1
union all
select f2.id, f2.category, f2.rangid, f2.nbidbycategory, cast(f1.rangconcat as varchar(500)) || ',' || cast(f2.id as varchar(500)) from cte f1 inner join tablewithrank f2 on f1.rangid=f2.rangid -1 and f1.category=f2.category
)
select category, rangconcat as IDS from cte
where rangid=nbidbycategory
Try this:
SELECT GROUP_CONCAT( field1, field2, field3 ,field4 SEPARATOR ', ')