I don't get where the error msg 'Illegal expression in WHEN clause of CASE expression' comes from by running this snippet in Teradata SQL
CASE
WHEN f_ev1.PROCESS_NO IN
(
SELECT
numbers.PROCESS_NO
FROM numbers
WHERE
numbers.FLAG = 1
GROUP BY 1 --no duplicates
) THEN 2
END AS Status,
If I write IN (some numbers) it works just fine. But it is a list that consists of 50 unique values that can possibly change over time.
My Suggestion is that you can load the fifty values into another table and you can join that table with the main table
table_50 - Table with 50 unique values
main_tbl - Main table
insert into table_50 ( process_no ) SELECT numbers.PROCESS_NO FROM numbers WHERE numbers.FLAG = 1 GROUP BY 1 ;
Select case when b.process_no is null then 2 end as status from main_table a
left join table_50 b
on a.process_no= b.process_no
From a performance perspective, this is more effective and you can also update the values in the table_50 as per your requirement
Related
I know that it's possible in other SQL flavors (T-SQL) to "select" provided data without a table. Like:
SELECT *
FROM (VALUES (1,2), (3,4)) tbl
How can I do this using Teradata?
Teradata has strange syntax for this:
select t.*
from (select * from (select 1 as a, 2 as b) x
union all
select * from (select 3 as a, 4 as b) x
) t;
I don't have access to a TD system to test, but you might be able to remove one of the nested SELECTs from the answer above:
select x.*
from (
select 1 as a, 2 as b
union all
select 3 as a, 4 as b
) x
If you need to generate some random rows, you can always do a SELECT from a system table, like sys_calendar.calendar:
SELECT 1, 2
FROM sys_calendar.calendar
SAMPLE 10;
Updated example:
SELECT TOP 1000 -- Limit to 1000 rows (you can use SAMPLE too)
ROW_NUMBER() OVER() MyNum, -- Sequential numbering
MyNum MOD 7, -- Modulo operator
RANDOM(1,1000), -- Random number between 1,1000
HASHROW(MyNum) -- Rowhash value of given column(s)
FROM sys_calendar.calendar; -- Use as table to source rows
A couple notes:
make sure you pick a system table that will always be present and have rows
if you need more rows than are available in the source table, do a UNION to get more rows
you can always easily create a one-column table and populate it to whatever number of rows you want by INSERT/SELECT into it:
CREATE DummyTable (c1 INT); -- Create table
INSERT INTO DummyTable(1); -- Seed table
INSERT INTO DummyTable SELECT * FROM DummyTable; -- Run this to duplicate rows as many times are you want
Then use this table to create whatever resultset you want, similar to the query above with sys_calendar.calendar.
I don't have a TD system to test so you might get syntax errors...but that should give you a basic idea.
I am a bit late to this thread, but recently got the same error.
I solved this by simply using
select distinct 1 as a, 2 as b from DBC.tables
union all
select distinct 3 as a, 4 as b from DBC.tables
Here, DBC.tables is a DB backend table with a few rows only. So, the query runs fast as well
I have 2 tables (A, B). They each have a different column that is basically an order or a sequence number. Table A has 'Sequence' and the values range from 0 to 5. Table B has 'Index' and the values are 16740, 16744, 16759, 16828, 16838, and 16990. Unfortunately I do not know the significance of these values. But I do believe they will always match in sequential order. I want to join these tables on these numbers where 0 = 16740, 1 = 16744, etc. Any ideas?
Thanks
You could use a case expression to convert table a's values to table b's values (or vise-versa) and join on that:
SELECT *
FROM a
JOIN b ON a.[sequence] = CASE b.[index] WHEN 16740 THEN 0
WHEN 16744 THEN 1
WHEN 16759 THEN 2
WHEN 16828 THEN 3
WHEN 16838 THEN 4
WHEN 16990 THEN 5
ELSE NULL
END;
#Mureinik has a great example. If down the road you do end up adding more numbers maybe putting this information into a new table would be a good idea.
CREATE TABLE C(
AInfo INT,
BInfo INT
)
INSERT INTO TABLE C(AInfo,BInfo) VALUES(0,16740)
INSERT INTO TABLE C(AInfo,BInfo) VALUES(1,16744)
etc
Then you can Join all the tables.
If the values are in ascending order as per your example, you can use the ROW_NUMBER() function to achieve this:
;with cte AS (SELECT *, ROW_NUMBER() OVER(ORDER BY [Index])-1 RN
FROM B)
SELECT *
FROM cte
I like to have my query count one column two times in my select based on the value. So for example.
input: table
id | type
-------------|-------------
1 | 1
2 | 1
3 | 2
4 | 2
5 | 2
output: query (in 1 row, not two):
countfirst = 2 (two times 1)
countsecond = 3 (three times 2)
An default count in an select counts all rows in the query. But i like to count rows based
on an number without limiting the query. When using for example WHERE type = '1', type 2
gets filtered and cannot be counted anymore.
Is there an solution for this case in SQL?
--- EXAMPLE USE (situation above is simplefied but case is the same) ---
With one query i get all cars grouped by type from an table. There are two type signs: yellow (in db 1) and grey (in db 2). So in that query i have the folowing output:
Renault - ten times found - two yellow signs - eight grey signs
Create a table, script is given below.
CREATE TABLE [dbo].[temptbl](
[id] [int] NULL,
[type] [int] NULL
) ON [PRIMARY]
Execute the insert script as
insert into [temptbl] values(1,1)
insert into [temptbl] values(2,1)
insert into [temptbl] values(3,2)
insert into [temptbl] values(4,2)
insert into [temptbl] values(5,2)
Then execute the query.
;WITH cte as(
SELECT [type], Count([type]) cnt
FROM temptbl
GROUP BY [type]
)
SELECT * FROM cte
pivot (Sum([cnt]) for [type] in ([1],[2])) as AvgIncomePerDay
You can use the GROUP BY clause as Mureinik suggested, but with the addition of a WHERE clause to filter the results.
Below shows the results for type = 1 (assuming type is an INT:
SELECT type, COUNT(*) AS NoOfRecords
FROM table
WHERE type IN (1)
GROUP BY type
So if we wanted 1 and 2 we can use:
SELECT type, COUNT(*) AS NoOfRecords
FROM table
WHERE type IN (1, 2)
GROUP BY type
Lastly, that IN statement can pull type from another query:
SELECT type, COUNT(*) AS NoOfRecords
FROM table
WHERE type IN (SELECT type FROM someOtherTable)
GROUP BY type
I want to show the number of times each distinct element in a column in a table in a SQL database appears, alongside the particular distinct element in a new output table. Is it possible in a single statement over ramming my head over it manually?
Without having actually tried, how about this:
SELECT tmp.Field, (SELECT COUNT(*) FROM [Table] t WHERE t.DesiredField = tmp.Field) AS Count
FROM
(
SELECT DISTINCT DesiredField FROM [Table]
) tmp
This would first select all distinct values from [Table] and in the outer select, take the values and the number of times they appear in the column.
You could also try
SELECT Field, SUM(1) AS Count FROM Table
GROUP BY Field
This should "flatten" the table so that it only contains distinct values in Field and the number of rows where Field has the same value.
I just tried the second - it seems to work nicely.
Turns out I was wrong all the time. The second example and the following actually return the same results:
SELECT Field, COUNT(*) AS Count FROM Table
GROUP BY Field
Simplest just to use COUNT(). You'll see varieties on what your count parameter, so here are the options.
DECLARE #tbl TABLE(id INT, data INT)
INSERT INTO #tbl VALUES (1,1),(2,1),(3,2),(4,NULL)
SELECT data
,COUNT(*) Count_star
,COUNT(id) Count_id
,COUNT(data) Count_data
,COUNT(1) Count_literal
FROM #tbl
GROUP BY data
data Count_star Count_id Count_data Count_literal
----------- ----------- ----------- ----------- -------------
NULL 1 1 0 1
1 2 2 2 2
2 1 1 1 1
Warning: Null value is eliminated by an aggregate or other SET operation.
You'll see the difference coming with the treatment of NULL if you COUNT a field that contains NULLs.
I've read and read and read but I haven't found a solution to my problem.
I'm doing something like:
SELECT a
FROM t1
WHERE t1.b IN (<external list of values>)
There are other conditions of course but this is the jist of it.
My question is: is there a way to show which in the manually entered list of values didn't find a match? I've looked but I can't find and I'm going in circles.
Create a temp table with the external list of values, then you can do:
select item
from tmptable t
where t.item not in ( select b from t1 )
If the list is short enough, you can do something like:
with t as (
select case when t.b1='FIRSTITEM' then 1 else 0 end firstfound
case when t.b1='2NDITEM' then 1 else 0 end secondfound
case when t.b1='3RDITEM' then 1 else 0 end thirdfound
...
from t1 wher t1.b in 'LIST...'
)
select sum(firstfound), sum(secondfound), sum(thirdfound), ...
from t
But with proper rights, I would use Nicholas' answer.
To display which values in the list of values haven't found a match, as one of the approaches, you could create a nested table SQL(schema object) data type:
-- assuming that the values in the list
-- are of number datatype
create type T_NumList as table of number;
and use it as follows:
-- sample of data. generates numbers from 1 to 11
SQL> with t1(col) as(
2 select level
3 from dual
4 connect by level <= 11
5 )
6 select s.column_value as without_match
7 from table(t_NumList(1, 2, 15, 50, 23)) s -- here goes your list of values
8 left join t1 t
9 on (s.column_value = t.col)
10 where t.col is null
11 ;
Result:
WITHOUT_MATCH
-------------
15
50
23
SQLFiddle Demo
There is no easy way to convert "a externally provided" list into a table that can be used to do the comparison. One way is to use one of the (undocumented) system types to generate a table on the fly based on the values supplied:
with value_list (id) as (
select column_value
from table(sys.odcinumberlist (1, 2, 3)) -- this is the list of values
)
select l.id as missing_id
from value_list l
left join t1 on t1.id = l.id
where t1.id is null;
There are ways to get what you have described, but they have requirements which exceed the statement of the problem. From the minimal description provided, there's no way to have the SQL return the list of the manually-entered values that did not match.
For example, if it's possible to insert the manually-entered values into a separate table - let's call it matchtbl, with the column named b - then the following should do the job:
SELECT matchtbl.b
FROM matchtbl
WHERE matchtbl.b NOT IN (SELECT distinct b
FROM t1)
Of course, if the data is being processed by a programming language, it should be relatively easy to keep track of the set of values returned by the original query, by adding the b column to the output, and then perform the set difference.
Putting the list in an in clause makes this hard. If you can put the list in a table, then the following works:
with list as (
select val1 as value from dual union all
select val2 from dual union all
. . .
select valn
)
select list.value, count(t1.b)
from list left outer join
t1
on t1.b = list.value
group by list.value;