I want to select from a table where column = 'n'. If the result has 0 rows, I want to remove that conditional.
Some pseudo-sql might be:
SELECT * FROM MY_TABLE
WHERE COL_A = 1 AND COL_B = 'mystring'
ELSE
SELECT * FROM MY_TABLE
WHERE COL_A = 1;
I will only be using the first row in either result, so it would also be acceptable to somehow sort the result such that rows where COL_B = 'mystring' appear at the top.
If you do not have too many values for each col_a value, you can use:
select t.*
from t
where col_a = 1
order by (case when col_b = 'mystring' then 1 else 2 end);
Just use the first row in the result set.
Assuming this is MSSQL:
SELECT
*
FROM
MY_TABLE
CROSS JOIN
(
SELECT
COUNT(*) c
FROM
MY_TABLE
WHERE
COL_A = 1
AND
COL_B = 'mystring'
) MY_WHERE_COUNT
WHERE (
MY_WHERE_COUNT.c > 0 AND MY_TABLE.COL_A = 1 AND MY_TABLE.COL_B = 'mystring'
)
OR (
MY_WHERE_COUNT.c = 0 AND MY_TABLE.COL_A = 1
)
Related
How to remove the 'All' DAT value rows which has multiple DAT values for 1 ID and one of them is 'All'. However if the val has only 'All' as the DAT value we should include those rows:
Sample input:
Sample output:
Any help would be appreciated. Thanks in advance!
If you just want a select query, then window functions can be helpful:
select t.*
from (select t.*,
sum( case when data <> 'All' then 1 else 0 end) over (partition by id, val) as cnt_notall
from t
) t
where not (data = 'All' and cnt_notall > 0);
DELETE FROM
your_table
WHERE
EXISTS (
SELECT *
FROM your_table lookup
WHERE lookup.id = your_table.id
AND lookup.val = your_table.val
AND lookup.dat <> 'All'
)
AND dat = 'All'
I have table:
Id Value
1 79868
2 79868
3 79868
4 97889
5 97889
Now, I want to make next select with bool variable that check if table contains difrent values at table column Value. Something like this:
select
v= (select case when exists(...)
then 1
else 0
end)
Table contais Values: 79868, 97889 so v should return 1 in other case 0.
How to write select iniside select case??
You can compare the min and max values:
select (case when (select min(value) from t) = (select max(value) from t)
then 1 else 0
end) as all_same
With an index on (value), this should be quite fast.
The above solution assumes that there are no null values or that NULL values should be ignored.
You might try this:
SELECT CASE COUNT(*)
WHEN 1 THEN 1
ELSE 0
END AS all_equal
FROM (SELECT DISTINCT Value FROM my_table);
If I get your question correct, you want to check if value column contains more than 1 distinct values. You can achieve this using,
select (case when count(value) > 1 then 1 else 0 end) as out
from (select value from table group by value) temp
May this is better:
SELECT CASE COUNT(DISTINCT value) WHEN 1 THEN 1
ELSE 0
END AS all_equal
FROM my_table;
So, you just need one case expression with two Boolean variable
declare #bit1 bit = 1, #bit0 bit = 0
select
(case when min(value) = max(value) then #bit1 else #bit0 end) as v
from table t
where value is not null
This is a the same as another answers
But is has some test data
declare #T table(pk int identity primary key, val int not null);
insert into #T (val) values (79868), (79868), (79868);
select case when count(distinct(val)) = 1 then 0 else 1 end as dd
from #t t;
select case when min(val) = max(val) then 0 else 1 end as dd
from #t t;
insert into #T (val) values (97889), (97889);
select case when count(distinct(val)) = 1 then 0 else 1 end as dd
from #t t;
select case when min(val) = max(val) then 0 else 1 end as dd
from #t t;
I like the min max answer from Gordon best
I have a SQL query which returns :
id | value
1 a
1 a
1 b
2 a
2 a
I want to get only id who have only the value a. So the id 2
How to do this ?
You can use aggregation and having clause to check if all the rows have value 'a' for a given id:
Using Count:
select id
from t
group by id
having count(*) = count(case when value = 'a' then 1 end);
Or using Sum
select id
from t
group by id
having SUM(case when value = 'a' then 0 else 1 end) = 0;
Use the next code:-
Select id
from #test
group by id
having sum (case when value = 'a' then 0 else 1 end) = 0
The clue is passing 0 for 'a' and pass 1 for other, then having sum equals 0
This is slightly slower than #Gurwinder Singh's answer but can be more readable if performance is not your top priority.
CREATE TABLE tmp (id int, [value] char(1))
INSERT INTO tmp values (1,'a'),(1,'a'),(1,'b'),(2,'a'),(2,'a')
SELECT DISTINCT id
FROM tmp a
WHERE [value] = 'a'
AND id NOT IN (
SELECT id FROM tmp
WHERE [value] <> 'a')
I have a huge query and I am wondering if it is in Oracle possible
to get the result of a case-when-statement and use it for comparison? My CASE-STATEMENT is declared in the Select-Statement and it looks like this.
SELECT........
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END) AS TEST;
Now I want to get the result of this case-statement and use it in the where part? Is it possible? (Sry this may be a dumb question)
If you define your CASE statement in either an inline-view or a common table expression (aka WITH clause), you can refer to it by whatever alias you give it.
For example (inline-view):
SELECT ...
FROM ( SELECT .....
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END) AS TEST
FROM...
) v
WHERE v.test = 'TEST2';
As a common table expression, it would be:
WITH cte AS ( SELECT........
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END) AS TEST
FROM ... )
SELECT ...
FROM cte
WHERE test = 'TEST2';
You can use a case statement in the where clause, for eg.:
select * from table
where table.field = (CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END)
This will compare the value returned from the case statement with the table field.
I am have a table with data and now i need to return zero in select statement if there is no records in table for example. I need to use it in Stored Procedure.
-- If no records exists in below select statement
SELECT ID,Text,Date FROM tblData WHERE ID = 12
IF (##ROWCOUNT = 0)
BEGIN
SELECT -5 AS ID
END
Output:
ID Text Date
ID
-5
Expected output
ID
-5
If you want to return 1 row even when there is no match, you can use aggregation:
SELECT (CASE WHEN COUNT(*) = 0 THEN -5 ELSE MAX(ID) END) as ID
FROM tblData
WHERE ID = 12;
I always use an Exists statment.
if exists(SELECT ID FROM tblData WHERE ID = 12)
select 0 as RowsExist
else
select 1 as RowsExist
For a single scalar value you could use something like;
SELECT ISNULL((SELECT ID FROM tblData WHERE ID = 12), 0) as ID
Rhys
SELECT (CASE WHEN Ta.ID IS NULL THEN TBL.ID
ELSE Ta.ID END) AS ID,Ta.Text,Ta.Date
FROM (VALUES(-5)) AS TBL(ID)
LEFT JOIN
(
SELECT ID,Text,Date FROM tblData WHERE ID = 12
)
AS Ta ON Ta.ID = Ta.ID