I am moving from using SQL Server to Postgresql and I am having trouble delcaring a variable.
In SQL Server I wrote something like this, which works just fine:
--Compute the probabilities for unique users
declare #users_total decimal(18,2)
select #users_total=count(*) from unique_users_table
select column1, uvs, uvs/#users_totalm as puvs
into probabilities_table
from column_uniquevisits_table
I attempted to translate it to Postgresql like so but got errors:
--Compute the probabilities for unique users
declare users_total numeric(18,2);
select users_total=count(*)
from unique_users_table
select coumn1, uvs, uvs/users_total as puvs
insert into probabilitiestable
from column_uniquevisits_table
What is the proper way of writing what I originally had in SQL Server in Postgresql?
If you want to create a table based on a select, use create table as select.
There is no need for a declare (which can't be used outside of a PL/pgSQL function anyway)
create table probabilitiestable
as
select column1,
uvs,
uvs::numeric/(select count(*) from count(*) from unique_users_table) as puvs
from column_uniquevisits_table;
The cast ::numeric is necessary because otherwise the division would be done with integer arithmetic which means you would not get any fractional valuues. If uvs is already defined as numeric (or decimal or float) then you don't need that.
I'd use a cross join to create the count to avoid the context switches and avoid multiple queries to the unique_users_table. The reason we can use a cross join is because we know the result of the query will always be 1 record. Thus it doesn't have a multiplication effect on the results.
CREATE table probabilitiestable as
SELECT column1, uvs, uvs/ut.users_total as puvs
FROM column_uniquevisits_table
CROSS JOIN (SELECT count(*) as users_total
FROM unique_users_Table) ut
Related
I would like to know if is it possible to use the clause "with as" with a variable and/or in a block begin/end.
My code is
WITH EDGE_TMP
AS
(select edge.node_beg_id,edge.node_end_id,prg_massif.longueur,prg_massif.lgvideoupartage,prg_massif.lgsanscable from prg_massif
INNER JOIN edge on prg_massif.asset_id=edge.asset_id
where prg_massif.lgvideoupartage LIKE '1' OR prg_massif.lgsanscable LIKE '1')
,
journey (TO_TOWN, STEPS,DISTANCE,WAY)
AS
(SELECT DISTINCT node_beg_id, 0, 0, CAST(&&node_begin AS VARCHAR2(2000))
FROM EDGE_TMP
WHERE node_beg_id = &&node_begin
UNION ALL
SELECT node_end_id, journey.STEPS + 1
, journey.DISTANCE + EDGE_TMP.longueur,
CONCAT(CONCAT(journey.WAY,';'), EDGE_TMP.node_end_id
)
It create a string as output separated by a ; but i need to get it back as variable or table do you know how? I used a concat to retrieve data in a big string. Can i use a table to insert data
,
A need to use the result to proceed more treatment.
Thank you,
mat
No, WITH is a part of an SQL statement only. But if you describe why you need it in pl/sql, we'll can advice you something.
Edit: if you have SQL statement which produces result you need, you can assign it's value to pl/sql variable. There are several methods to do this, simpliest is to use SELECT INTO statement (add INTO variable clause into your select).
You can use WITH clause as a part of SELECT INTO statement (at least in not-too-very-old Oracle versions).
I am fairly new to SQL, and I am hoping someone can help me with a problem I'm having. I haven't been able to find any answers helping me figure out this exact problem.
I have two tables in two SQL Server databases on two different servers that I want to compare using the column ItemID. I want to find records from Table1 that have an ItemID that does not exist in Table2 and insert those into a table variable. I have the following code:
--Create table variable to hold query results
DECLARE #ItemIDTable TABLE
(
[itemid][NVARCHAR](20) NULL
);
--Query data and insert results into table variable
INSERT INTO #ItemIDTable
([itemid])
SELECT a.[itemid]
FROM database1.dbo.table1 a
WHERE NOT EXISTS (SELECT 1
FROM [Database2].[dbo].[table2]
WHERE a.itemid = [Database2].[dbo].[table2].[itemid])
ORDER BY itemid
This works on a test server where the two databases are on the same server, but not in real life where they are on different servers. I tried the following using OPENQUERY, but I know I haven't got it quite right.
--Create table variable to hold query results
DECLARE #ItemIDTable TABLE
(
[ItemID][nvarchar](20) NULL
);
--Query data and insert results into table variable
INSERT INTO #ItemIDTable
([ItemID])
SELECT a.[ItemID]
FROM Database1.dbo.Table1 a
WHERE NOT EXISTS (SELECT 1
FROM OPENQUERY([Server2], SELECT * FROM [Database2].[dbo].[Table2]')
WHERE a.ItemID = [Database2].[dbo].[Table2].[ItemID])
ORDER BY ItemID
I'm pretty sure I need to do something in the WHERE clause, where I have the two databases on two servers, I'm just not quite sure how to structure it. Could anyone help?
You can't create an OPENQUERY that is correlated to an outer query. You could populate a temp table with the results of an OPENQUERY and do your WHERE NOT EXISTS against the temp table, or you might want to look into Synonyms.
Openquery works like this:
select *
from openquery
(LINKED_SERVER_NAME,
'select query goes here'
)
Note that the sql portion is single quoted. That means you might have to quote the quotes if necessary. For example:
select *
from openquery
(LINKED_SERVER_NAME,
'
select SomeTextField
from SomeTable
where SomeDateField = ''20141014''
'
)
I couldn't find solution for this problem.
I have table A with primary key ROW_ID, table B with same extern key and column SOMETHING.
Also, I have function created like this:
CREATE FUNCTION FIND_SOMETHING_FOR_ID(ROW_ID INTEGER)
RETURNS TABLE(SOMETHING INTEGER)
BEGIN ATOMIC
RETURN
SELECT SOME_SCALAR_FUNCTION(SOMETHING)
FROM B b
WHERE b.ROW_ID=ROW_ID;
END#
The thing I want to do is: for each ROW_ID in A get table returned by FIND_SOMETHING_FOR_ID
and then get UNION of all tables.
According to the documentation, you can do what you want as:
select fsfi.*
from A a cross join
table(find_something_for_id(a.row_id)) fsfi;
That is, a table-valued function can reference tables before it in the from clause, but not after it. (Note: I replaced the , in the from with cross join because I abhor commas in the from clause.)
By the way, SQL Server solves this problem with the cross apply operator.
Debugging an app which queries SQL Server 05, can't change the query but need to optimise things.
Running all the selects seperately are quick <1sec, eg: select * from acscard, select id from employee... When joined together it takes 50 seconds.
Is it better to set uninteresting accesscardid fields to null or to '' when using EXISTS?
SELECT * FROM ACSCard
WHERE NOT EXISTS
( SELECT Id FROM Employee
WHERE Employee.AccessCardId = ACSCard.acs_card_number )
AND NOT EXISTS
( SELECT Id FROM Visit
WHERE Visit.AccessCardId = ACSCard.acs_card_number )
ORDER by acs_card_id
Do you have indexes on Employee.AccessCardId, Visit.AccessCardId, and ACSCard.acs_card_number?
The SELECT clause is not evaluated in an EXISTS clause. This:
WHERE EXISTS(SELECT 1/0
FROM EMPLOYEE)
...should raise an error for dividing by zero, but it won't. But you need to put something in the SELECT clause for it to be a valid query - it doesn't matter if it's NULL or a zero length string.
In SQL Server, NOT EXISTS (and NOT IN) are better than the LEFT JOIN/IS NULL approach if the columns being compared are not nullable (the values on either side can not be NULL). The columns compared should be indexed, if they aren't already.
Is there a better solution to the problem of looking up multiple known IDs in a table:
SELECT * FROM some_table WHERE id='1001' OR id='2002' OR id='3003' OR ...
I can have several hundreds of known items. Ideas?
SELECT * FROM some_table WHERE ID IN ('1001', '1002', '1003')
and if your known IDs are coming from another table
SELECT * FROM some_table WHERE ID IN (
SELECT KnownID FROM some_other_table WHERE someCondition
)
The first (naive) option:
SELECT * FROM some_table WHERE id IN ('1001', '2002', '3003' ... )
However, we should be able to do better. IN is very bad when you have a lot of items, and you mentioned hundreds of these ids. What creates them? Where do they come from? Can you write a query that returns this list? If so:
SELECT *
FROM some_table
INNER JOIN ( your query here) filter ON some_table.id=filter.id
See Arrays and Lists in SQL Server 2005
ORs are notoriously slow in SQL.
Your question is short on specifics, but depending on your requirements and constraints I would build a look-up table with your IDs and use the EXISTS predicate:
select t.id from some_table t
where EXISTS (select * from lookup_table l where t.id = l.id)
For a fixed set of IDs you can do:
SELECT * FROM some_table WHERE id IN (1001, 2002, 3003);
For a set that changes each time, you might want to create a table to hold them and then query:
SELECT * FROM some_table WHERE id IN
(SELECT id FROM selected_ids WHERE key=123);
Another approach is to use collections - the syntax for this will depend on your DBMS.
Finally, there is always this "kludgy" approach:
SELECT * FROM some_table WHERE '|1001|2002|3003|' LIKE '%|' || id || '|%';
In Oracle, I always put the id's into a TEMPORARY TABLE to perform massive SELECT's and DML operations:
CREATE GLOBAL TEMPORARY TABLE t_temp (id INT)
SELECT *
FROM mytable
WHERE mytable.id IN
(
SELECT id
FROM t_temp
)
You can fill the temporary table in a single client-server roundtrip using Oracle collection types.
We have a similar issue in an application written for MS SQL Server 7. Although I dislike the solution used, we're not aware of anything better...
'Better' solutions exist in 2008 as far as I know, but we have Zero clients using that :)
We created a table valued user defined function that takes a comma delimited string of IDs, and returns a table of IDs. The SQL then reads reasonably well, and none of it is dynamic, but there is still the annoying double overhead:
1. Client concatenates the IDs into the string
2. SQL Server parses the string to create a table of IDs
There are lots of ways of turning '1,2,3,4,5' into a table of IDs, but the Stored Procedure which uses the function ends up looking like...
CREATE PROCEDURE my_road_to_hell #IDs AS VARCHAR(8000)
AS
BEGIN
SELECT
*
FROM
myTable
INNER JOIN
dbo.fn_split_list(#IDs) AS [IDs]
ON [IDs].id = myTable.id
END
The fastest is to put the ids in another table and JOIN
SELECT some_table.*
FROM some_table INNER JOIN some_other_table ON some_table.id = some_other_table.id
where some_other_table would have just one field (ids) and all values would be unique