I need the below results ..
Table :
Order postcode qnty
123 2234 1
Expected result:
Order 123
Postcode 2234
Qnty 1
SQL server:
Select pvt.element_name
,pvt.element_value(select order.postcode
from table name)up
unpivot (element_value for element_name in(order,postcode) as Pvt
How to achieve this in db2?
Db2 for IBM i doesn't have a built-in unpviot function.. AFAIK, it's not available on any Db2 platofrm...unless it's been added recently.
The straight forward method
select 'ORDER' as key, order as value
from mytable
UNION ALL
select 'POSTCODE', postcode
from mytable
UNION ALL
select 'QNTY', char(qnty)
from mytable;
A better performing method is to do a cross join between the source table and a correlated VALUES of as many rows as columns that need to be unpivoted.
select
Key, value
from mytable T,
lateral (values ('ORDER', t.order)
, ('POSTCODE', t.postcode)
, ('QNQTY', varchar(t.qnty))
) as unpivot(key, value);
However, you'll need to know ahead of time what the values you're unpivoting on.
If you don't know the values, there are some ways to unpivot with the XMLTABLE (possibly JSON_TABLE) that might work. I've never used them, and I'm out of time to spend answering this question. You can find some examples via google.
I have created a stored procedure for LUW that rotate a table:
https://github.com/angoca/db2tools/blob/master/pivot.sql
You just need to call the stored procedure by passing the tablename as parameter, and it will return a cursor with the headers of the column in the first column.
Related
Documentation provides an example of using the pivot() function.
SELECT *
FROM (SELECT partname, price FROM part) PIVOT (
AVG(price) FOR partname IN ('prop', 'rudder', 'wing')
);
I would like to use pivot() without having to manually specify each value of partname. I want all parts. I tried:
SELECT *
FROM (SELECT partname, price FROM part) PIVOT (
AVG(price) FOR partname);
That gave an error. Then tried:
SELECT *
FROM (SELECT partname, price FROM part) PIVOT (
AVG(price) FOR partname IN (select distinct partname from part)
);
That also threw an error.
How can I tell Redshift to include all values of partname in the pivot?
I don't think this can be done in a simple single query. This would mean that the query compiler would need to work without knowing how many output columns will be produced. I don't think it can do that.
You can do this in multiple queries - use a query to create the list of partnames and then use this to "generate" a second query that populates the IN list. So something needs issue these queries and generated the second. This can be some code external to Redshift (lots of options) or a stored procedure in Redshift. This code, no matter where it exists, should understand that Redshift has a max number of columns limit - 1,600.
The Redshift docs are fairly good on the topic of dynamic SQL for stored procedures. The EXECUTE statement will be used to fire off the second query in a stored procedure. See: https://docs.aws.amazon.com/redshift/latest/dg/c_PLpgSQL-statements.html
ّ am trying to insert multiple records got from the join table to another table user_to_property. In the user_to_property table user_to_property_id is primary, not null it is not autoincrementing. So I am trying to add user_to_property_id manually by an increment of 1.
WITH selectedData AS
( -- selection of the data that needs to be inserted
SELECT t2.user_id as userId
FROM property_lines t1
INNER JOIN user t2 ON t1.account_id = t2.account_id
)
INSERT INTO user_to_property (user_to_property_id, user_id, property_id, created_date)
VALUES ((SELECT MAX( user_to_property_id )+1 FROM user_to_property),(SELECT
selectedData.userId
FROM selectedData),3,now());
The above query gives me the below error:
ERROR: more than one row returned by a subquery used as an expression
How to insert multiple records to a table from the join of other tables? where the user_to_property table contains a unique record for the same user-id and property_id there should be only 1 record.
Typically for Insert you use either values or select. The structure values( select...) often (generally?) just causes more trouble than it worth, and it is never necessary. You can always select a constant or an expression. In this case convert to just select. For generating your ID get the max value from your table and then just add the row_number that you are inserting: (see demo)
insert into user_to_property(user_to_property_id
, user_id
, property_id
, created
)
with start_with(current_max_id) as
( select max(user_to_property_id) from user_to_property )
select current_max_id + id_incr, user_id, 3, now()
from (
select t2.user_id, row_number() over() id_incr
from property_lines t1
join users t2 on t1.account_id = t2.account_id
) js
join start_with on true;
A couple notes:
DO NOT use user for table name, or any other object name. It is a
documented reserved word by both Postgres and SQL standard (and has
been since Postgres v7.1 and the SQL 92 Standard at lest).
You really should create another column or change the column type
user_to_property_id to auto-generated. Using Max()+1, or
anything based on that idea, is a virtual guarantee you will generate
duplicate keys. Much to the amusement of users and developers alike.
What happens in an MVCC when 2 users run the query concurrently.
I'm working on a table which has more than 10 columns. One of the column name is ASAT which is of type DATE(Format is yyyy-mm-dd HH:MM:SS:mmm).
I'm looking for a sql query which returns all records of max date. Trying to use that query in java for JDBC call.
I tried this:
Select * from tablename where ASAT in (select MAX(ASAT) from tablename).
But it is not returning any records.
Any help is really appreciated.Thanks
How about:
SELECT MAX(Asat) FROM TableA;
SELECT MAX(Asat) FROM TableA GROUP BY Asat;
When you self join, I suggest aliasing each copy of the table. Personally I use the table letter with a number afterwards in case I need to track it for larger queries.
Select *
from tablename t1
where t1.ASAT = (
select MAX(t2.ASAT)
from tablename t2
)
I believe you are looking for something like this if I'm understanding you. First build a CTE containing the primary key and the MAX(ASAT). Then join to it, selecting where the primary key matches the primary key of the row with the MAX(ASAT). Note your "ID" may have to be more than one column.
with tbl_max_asat(id, max_asat) as (
select id, max(asat) max_asat
from tablename
group by id
)
select *
from tablename t
join tbl_max_asat tma
on t.id = tma.id;
This old post just popped up because it was edited today. Maybe my answer will still help someone. :-)
I thought I understood how I can do a SELECT from the results of another SELECT statement, but there seems to be some sort of blurring of scope that I don't understand. I am using SQL Server 2008R2.
It is easiest to explain with an example.
Create a table with a single nvarchar column - load the table with a single text value and a couple of numbers:
CREATE TABLE #temptable( a nvarchar(30) );
INSERT INTO #temptable( a )
VALUES('apple');
INSERT INTO #temptable( a )
VALUES(1);
INSERT INTO #temptable( a )
VALUES(2);
select * from #temptable;
This will return: apple, 1, 2
Use IsNumeric to get only the rows of the table that can be cast to numeric - this will leave the text value apple behind. This works fine.
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1 ;
This returns: 1, 2
However, if I use that exact same query as an inner select, and try to do a numeric WHERE clause, it fails saying cannot convert nvarchar value 'apple' to data type int. How has it got the value 'apple' back??
select
x.NumA
from
(
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1
) x
where x.NumA > 1
;
Note that the failing query works just fine without the WHERE clause:
select
x.NumA
from
(
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1
) x
;
I find this very surprising. What am I not getting? TIA
If you take a look at the estimated execution plan you'll find that it has optimized the inner query into the outer and combined the WHERE clauses.
Using a CTE to isolate the operations works (in SQL Server 2008 R2):
declare #temptable as table ( a nvarchar(30) );
INSERT INTO #temptable( a )
VALUES ('apple'), ('1'), ('2');
with Numbers as (
select cast(a as int) as NumA
from #temptable
where IsNumeric(a) = 1
)
select * from Numbers
The reason you are getting this is fair and simple. When a query is executed there are some steps that are being followed. This is a parse, algebrize, optimize and compile.
The algebrize part in this case will get all the objects you need for this query. The optimize will use these objects to create a best query plan which will be compiled and executed...
So, when you look into that part you will see it will do a table scan on #temptable. And #temptable is defined as the way you created your table. That you will do some compute on it is a different thing..... The column still has the nvarchar datatype..
To know how this works you have to know how to read a query. First all the objects are retrieved (from table, inner join table), then the predicates (where, on), then the grouping and such, then the select of the columns (with the cast) and then the orderby.
So with that in mind, when you have a combination of selects, the optimizer will still process it that way.. since your select is subordinate to the from and join parts of your query, it will be a reason for getting this error.
I hope i made it a little clear?
The optimizer is free to move expressions in the query plan in order to produce the most cost efficient plan for retrieving the data (the evaluation order of the predicates is not guaranteed). I think using the case expression like bellow produces a NULL in absence of the ELSE clause and thus takes the APPLE out
select a from #temptable where case when isnumeric(a) = 1 then a end > 1
I've got two SQL2008 tables, one is a "Import" table containing new data and the other a "Destination" table with the live data. Both tables are similar but not identical (there's more columns in the Destination table updated by a CRM system), but both tables have three "phone number" fields - Tel1, Tel2 and Tel3. I need to remove all records from the Import table where any of the phone numbers already exist in the destination table.
I've tried knocking together a simple query (just a SELECT to test with just now):
select t2.account_id
from ImportData t2, Destination t1
where
(t2.Tel1!='' AND (t2.Tel1 IN (t1.Tel1,t1.Tel2,t1.Tel3)))
or
(t2.Tel2!='' AND (t2.Tel2 IN (t1.Tel1,t1.Tel2,t1.Tel3)))
or
(t2.Tel3!='' AND (t2.Tel3 IN (t1.Tel1,t1.Tel2,t1.Tel3)))
... but I'm aware this is almost certainly Not The Way To Do Things, especially as it's very slow. Can anyone point me in the right direction?
this query requires a little more that this information. If You want to write it in the efficient way we need to know whether there is more duplicates each load or more new records. I assume that account_id is the primary key and has a clustered index.
I would use the temporary table approach that is create a normalized table #r with an index on phone_no and account_id like
SELECT Phone, Account into #tmp
FROM
(SELECT account_id, tel1, tel2, tel3
FROM destination) p
UNPIVOT
(Phone FOR Account IN
(Tel1, tel2, tel3)
)AS unpvt;
create unclustered index on this table with the first column on the phone number and the second part the account number. You can't escape one full table scan so I assume You can scan the import(probably smaller). then just join with this table and use the not exists qualifier as explained. Then of course drop the table after the processing
luke
I am not sure on the perforamance of this query, but since I made the effort of writing it I will post it anyway...
;with aaa(tel)
as
(
select Tel1
from Destination
union
select Tel2
from Destination
union
select Tel3
from Destination
)
,bbb(tel, id)
as
(
select Tel1, account_id
from ImportData
union
select Tel2, account_id
from ImportData
union
select Tel3, account_id
from ImportData
)
select distinct b.id
from bbb b
where b.tel in
(
select a.tel
from aaa a
intersect
select b2.tel
from bbb b2
)
Exists will short-circuit the query and not do a full traversal of the table like a join. You could refactor the where clause as well, if this still doesn't perform the way you want.
SELECT *
FROM ImportData t2
WHERE NOT EXISTS (
select 1
from Destination t1
where (t2.Tel1!='' AND (t2.Tel1 IN (t1.Tel1,t1.Tel2,t1.Tel3)))
or
(t2.Tel2!='' AND (t2.Tel2 IN (t1.Tel1,t1.Tel2,t1.Tel3)))
or
(t2.Tel3!='' AND (t2.Tel3 IN (t1.Tel1,t1.Tel2,t1.Tel3)))
)