I have a table that consists of potentially multiple sequences to each schedules. I would like to output a single (latest) record from each sequence. Below is an example of the table, and the output I'm looking for:
Table sample:
Expected output:
The table name is dataschedule - could you let me know how to best write the sql query to get this data? Thank you!
Hmmm . . . if you want the latest sequence, you can use a correlated subquery:
select t.*
from t
where t.sequence = (select max(t2.sequence)
from t t2
where t2.schedule = t.schedule and t2.id = t.id
);
In most databases, this has quite good performance with an index on (id, schedule, sequence).
Please try this, i havent tested it as you dint provide the insert and create table scripts. Just replace table_name by you table name.
select table_name.*
from table_name, (select ID,schedule,max(sequence) from table_name group by ID,schedule) a
where
table_name.ID = a.ID and
table_name.schedule = a.schedule ;
Related
I'd like to create 3-4 separate temporary tables within a single BigQuery query (all of the tables are based on different data sources) and then join them in various ways later on in the query.
I'm trying to do this by using multiple WITH statements, but it appears that you're only able to use one WITH statement in a query if you're not nesting them. Each time I've tried, I get an error saying that a 'SELECT' statement is expected.
Am I missing something? I'd prefer to do this all in one query if at all possible.
I don't know what you mean by "temporary tables", but I suspect you mean common table expressions (CTEs).
Of course you can have a query with multiple CTEs. You just need the right syntax:
with t1 as (
select . . .
),
t2 as (
select . . .
),
t3 as (
select . . .
)
select *
from t1 cross join t2 cross join t3;
bq mk --table --expiration [INTEGER] --description "[DESCRIPTION]"
--label [KEY:VALUE, KEY:VALUE] [PROJECT_ID]:[DATASET].[TABLE]
Expiration date will make your table temporary. You can create one table at the time with "bq mk" but you can use this in a script.
You can use the DDL, but here also you can only create one table at the time.
{CREATE TABLE | CREATE TABLE IF NOT EXISTS | CREATE OR REPLACE TABLE}
table_name [( column_name column_schema[, ...] )]
[PARTITION BY partition_expression] [OPTIONS(options_clause[, ...])]
[AS query_statement]
If by "temporary table" you meant "subqueries" this is the syntax you have to use:
WITH
subQ1 AS (
SELECT * FROM Roster
WHERE SchoolID = 52),
subQ2 AS (
SELECT SchoolID FROM subQ1)
SELECT DISTINCT * FROM subQ2;
You should be able to use common table expressions without issue. However, if you have large queries with a significant amount of common table expressions/subqueries you may run into resource issues in BQ specifically regarding the ability for BQ to create an execution plan. Temporary tables have helped me in these scenarios, but there are likely better practices.
CREATE TEMP TABLE T1 AS (
WITH
X as (query),
Y as (query),
Z as (query)
SELECT * FROM
(combination_of_above_queries)
);
CREATE TEMP TABLE T2 AS (
WITH
A as (query),
B as (query),
C as (query)
SELECT * FROM
(combination_of_above_queries)
);
CREATE TABLE new_table AS (
SELECT *
FROM (combination of T1 and T2)
)
Apologies, I just saw happened to come across this question and wanted to share what helped me... hope it is helpful for you.
https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language#temporary_tables
I currently have the table as follows on the picture.
I would like to write a query which returns all the names and the travel_date with the maximal 'total' value for each name. For example, I would like the query to return in this case:
Armand 2012-07-18 and Elish 2012-06-18. How could I do that ? Thanks in advance
In most cases, you'll find that the procedure for this is relatively universal. The following example will work in MySQL, MSSQL and DB2 (among others).
SELECT
a.name,
a.travel_date,
a.total
FROM test_table AS a
INNER JOIN ( SELECT `name`, MAX(total) AS `total` FROM test_table GROUP BY `name` ) AS b
ON a.name = b.name
AND a.total = b.total;
Here's an example of the sample data I worked with including the results after running the query.
-
Edit: As jarlh, the initial query I wrote was indeed wrong. The following query should provide the results that you requested in the comment below.
SELECT name, MAX(travel_date)
FROM my_table
GROUP BY name;
I have a component that retrieves data from database based on the keys provided.
However I want my java application to get all the data for all keys in a single database hit to fasten up things.
I can use 'in' clause when I have only one key.
While working on more than one key I can use below query in oracle
SELECT * FROM <table_name>
where (value_type,CODE1) IN (('I','COMM'),('I','CORE'));
which is similar to writing
SELECT * FROM <table_name>
where value_type = 1 and CODE1 = 'COMM'
and
SELECT * FROM <table_name>
where value_type = 1 and CODE1 = 'CORE'
together
However, this concept of using 'in' clause as above is giving below error in 'SQL server'
ERROR:An expression of non-boolean type specified in a context where a condition is expected, near ','.
Please let know if their is any way to achieve the same in SQL server.
This syntax doesn't exist in SQL Server. Use a combination of And and Or.
SELECT *
FROM <table_name>
WHERE
(value_type = 1 and CODE1 = 'COMM')
OR (value_type = 1 and CODE1 = 'CORE')
(In this case, you could make it shorter, because value_type is compared to the same value in both combinations. I just wanted to show the pattern that works like IN in oracle with multiple fields.)
When using IN with a subquery, you need to rephrase it like this:
Oracle:
SELECT *
FROM foo
WHERE
(value_type, CODE1) IN (
SELECT type, code
FROM bar
WHERE <some conditions>)
SQL Server:
SELECT *
FROM foo
WHERE
EXISTS (
SELECT *
FROM bar
WHERE <some conditions>
AND foo.type_code = bar.type
AND foo.CODE1 = bar.code)
There are other ways to do it, depending on the case, like inner joins and the like.
If you have under 1000 tuples you want to check against and you're using SQL Server 2008+, you can use a table values constructor, and perform a join against it. You can only specify up to 1000 rows in a table values constructor, hence the 1000 tuple limitation. Here's how it would look in your situation:
SELECT <table_name>.* FROM <table_name>
JOIN ( VALUES
('I', 'COMM'),
('I', 'CORE')
) AS MyTable(a, b) ON a = value_type AND b = CODE1;
This is only a good idea if your list of values is going to be unique, otherwise you'll get duplicate values. I'm not sure how the performance of this compares to using many ANDs and ORs, but the SQL query is at least much cleaner to look at, in my opinion.
You can also write this to use EXIST instead of JOIN. That may have different performance characteristics and it will avoid the problem of producing duplicate results if your values aren't unique. It may be worth trying both EXIST and JOIN on your use case to see what's a better fit. Here's how EXIST would look,
SELECT * FROM <table_name>
WHERE EXISTS (
SELECT 1
FROM (
VALUES
('I', 'COMM'),
('I', 'CORE')
) AS MyTable(a, b)
WHERE a = value_type AND b = CODE1
);
In conclusion, I think the best choice is to create a temporary table and query against that. But sometimes that's not possible, e.g. your user lacks the permission to create temporary tables, and then using a table values constructor may be your best choice. Use EXIST or JOIN, depending on which gives you better performance on your database.
Normally you can not do it, but can use the following technique.
SELECT * FROM <table_name>
where (value_type+'/'+CODE1) IN (('I'+'/'+'COMM'),('I'+'/'+'CORE'));
A better solution is to avoid hardcoding your values and put then in a temporary or persistent table:
CREATE TABLE #t (ValueType VARCHAR(16), Code VARCHAR(16))
INSERT INTO #t VALUES ('I','COMM'),('I','CORE')
SELECT DT. *
FROM <table_name> DT
JOIN #t T ON T.ValueType = DT.ValueType AND T.Code = DT.Code
Thus, you avoid storing data in your code (persistent table version) and allow to easily modify the filters (without changing the code).
I think you can try this, combine and and or at the same time.
SELECT
*
FROM
<table_name>
WHERE
value_type = 1
AND (CODE1 = 'COMM' OR CODE1 = 'CORE')
What you can do is 'join' the columns as a string, and pass your values also combined as strings.
where (cast(column1 as text) ||','|| cast(column2 as text)) in (?1)
The other way is to do multiple ands and ors.
I had a similar problem in MS SQL, but a little different. Maybe it will help somebody in futere, in my case i found this solution (not full code, just example):
SELECT Table1.Campaign
,Table1.Coupon
FROM [CRM].[dbo].[Coupons] AS Table1
INNER JOIN [CRM].[dbo].[Coupons] AS Table2 ON Table1.Campaign = Table2.Campaign AND Table1.Coupon = Table2.Coupon
WHERE Table1.Coupon IN ('0000000001', '0000000002') AND Table2.Campaign IN ('XXX000000001', 'XYX000000001')
Of cource on Coupon and Campaign in table i have index for fast search.
Compute it in MS Sql
SELECT * FROM <table_name>
where value_type + '|' + CODE1 IN ('I|COMM', 'I|CORE');
I need to make a query but get the value in every field empty. Gordon Linoff give me the clue to this need here:
SQL Empty query results
which is:
select t.*
from (select 1 as val
) v left outer join
table t
on 1 = 0;
This query wors perfectly on PostgreSQL but gets an error when trying to execute it in Microsoft Access, it says that 1 = 0 expression is not admitted. How could it be fixed to work on microsoft access?
Regards,
If the table has a numeric primary key column whose values are non-negative then the following query will work in Access. The primary key field is [ID].
SELECT t2.*
FROM
myTable AS t2
RIGHT JOIN
(
SELECT TOP 1 (ID * -1) AS badID
FROM myTable AS t1
) AS rowStubs
ON t2.ID = rowStubs.badID
This was tested with Access 2010.
I am offering this answer here, even though you didn't think it worked in my edit to your original question. What is the problem?
select t.*
from (select max(col) as maxval from table as t
) as v left join
table as t
on v.val < t.col;
You can use the following query, but it would still need a little "manual coding".
EDITS:
Actually, you do not need the SWITCH function. Modified query below.
Removed the reference to Description column from one line. Still, you would need to use a Text column name (such as Description) in the last line of the query.
For example, the following query would work for the Months table:
select Months.*
from Months
RIGHT OUTER JOIN
(select "" as DummyColumn from Months) Blank_Data
ON Months.Description = Blank_Data.DummyColumn; --hardcoded Description column
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