Suppose there is a Table with 2 columns and the following data:
ID : 1,2,3,4,5,6,7,8
DATA:a,a,a,a,a,a,a,b
There can be only one 1 row with DATA=b and multiple rows with DATA=a.
I need a query that will select only one row.If there is any row with DATA=b then we will select that and if there is no row with DATA=b then it will select the first row with DATA=a.
Please Help!!!!
SELECT *
FROM table
WHERE DATA in ('A', 'B')
ORDER BY CASE WHEN DATA= 'B' THEN 0 ELSE 1 END, ID
FETCH FIRST 1 ROWS ONLY
Related
I like to count the number of appearance of my users in more then one column. This is how I count the values in columns:
SELECT COUNT(col_01) FROM table_01 WHERE col_01 = 'John' // result: 2
SELECT COUNT(col_02) FROM table_01 WHERE col_02 = 'John' // result: 4
Is there any way to count John in one step in all columns I have and get the results 6?
Thank you in advance!
First filter the table so that you get only the rows with 'John' in any of the 2 columns and then use aggregate function TOTAL() on each column:
SELECT TOTAL(col_01 = 'John') + TOTAL(col_02 = 'John') AS total
FROM table_01
WHERE 'John' IN (col_01, col_02);
Try conditional aggregation
select
sum(case when col_01='John' then 1 end) +
sum(case when col_02='John' then 1 end)
from table_01;
I have a table with 5 columns in each row, I want to select * when status column =1 and see just date and status columns if it is not =1
I think this is better, because the union makes the query run very slow.
SELECT date,
status,
CASE WHEN status = 1 THEN asd end as asd,
CASE WHEN status = 1 THEN asd1 end as asd1,
...
FROM table
I have to create a new table and inside should be the columns I get from the CASE statement. I do not need the rest of the columns resulting from the select statement
for example:
CREATE TABLE test
AS (
SELECT a.id, ...
CASE WHEN a.id = 1 THEN 2
ELSE 0
END as LegalType
FROM table a, ...
WHERE ...);
now my question how can I select only the column LegalType from the CASE statement? I do not want to have column a.id
You can SELECT INTO
SELECT CASE WHEN a.id = 1 THEN 2 ELSE 0 END as LegalType
....
INTO test
FROM table a
WHERE 1=1);
This will create you a table based on the data returned in the SELECT. see https://msdn.microsoft.com/en-GB/library/ms188029.aspx
This question already has answers here:
Return a value if no record is found
(6 answers)
Get 0 value from a count with no rows
(6 answers)
Closed 7 years ago.
I have a simple query:
Select qty from X where id=....;
this query always return 0 or 1 row.
when it return 1 row everything works.
but if it return 0 rows my query fails as qty is used in calculations. (This is acatually a Sub query in Select statment).
I need somehow to make sure the query always return 1 row.
I tried:
Select coalesce(qty,0) from X where id=....;
but it doesn't help as if there are no rows the coalesce is useless.
if no row found it should give 0
How can I fix it?
You can do this:
SELECT COALESCE( (SELECT qty from X where id=....), 0)
if nothing is returned from the inner SELECT statement, COALESCE will give you 0 in the outer SELECT statement.
Select *.a from (
Select qty, 0 as priority from X where id=....
Union
Select 0, 1 as priority
) a
Order By a.priority Asc
Limit 1
This select basically ensures that at least one row is returned by adding an additional row to the end and by adding the limit statement we just return the first row.
So now there is the case where at least one row is found and the additional row is added to the end. In this case the first row found (see ->) will be returned due to the ascending order by priority:
qty priority
-> 1 0
3 0
4 0
. .
0 1
And then there is the case where no row is found but the additional row is returned:
qty priority
-> 0 1
try this.
SELECT COALESCE((SELECT qty
FROM x
WHERE id = #MyIdVar), 1)
If no records found then its return 'No rows found'
if not exists(Select * from table where condition=...)
Begin
Select * from table where condition=...
End
Else
Begin
Select 'No rows found'
End
Whenever you use this you will get record else no record found message.
Without using COALESCE()
select qty from X where id=1 UNION SELECT 0 order by qty desc limit 1
Demo
I am writing data to a table and allocating a "group-id" for each batch of data that is written. To illustrate, consider the following table.
GroupId Value
------- -----
1 a
1 b
1 c
2 a
2 b
3 a
3 b
3 c
3 d
In this example, there are three groups of data, each with similar but varying values.
How do I query this table to find a group that contains a given set of values? For instance, if I query for (a,b,c) the result should be group 1. Similarly, a query for (b,a) should result in group 2, and a query for (a, b, c, e) should result in the empty set.
I can write a stored procedure that performs the following steps:
select distinct GroupId from Groups -- and store locally
for each distinct GroupId: perform a set-difference (except) between the input and table values (for the group), and vice versa
return the GroupId if both set-difference operations produced empty sets
This seems a bit excessive, and I hoping to leverage some other commands in SQL to simplify. Is there a simpler way to perform a set-comparison in this context, or to select the group ID that contains the exact input values for the query?
This is a set-within-sets query. I like to solve it using group by and having:
select groupid
from GroupValues gv
group by groupid
having sum(case when value = 'a' then 1 else 0 end) > 0 and
sum(case when value = 'b' then 1 else 0 end) > 0 and
sum(case when value = 'c' then 1 else 0 end) > 0 and
sum(case when value not in ('a', 'b', 'c') then 1 else - end) = 0;
The first three conditions in the having clause check that each elements exists. The last condition checks that there are no other values. This method is quite flexible, for various exclusions and inclusion conditions on the values you are looking for.
EDIT:
If you want to pass in a list, you can use:
with thelist as (
select 'a' as value union all
select 'b' union all
select 'c'
)
select groupid
from GroupValues gv left outer join
thelist
on gv.value = thelist.value
group by groupid
having count(distinct gv.value) = (select count(*) from thelist) and
count(distinct (case when gv.value = thelist.value then gv.value end)) = count(distinct gv.value);
Here the having clause counts the number of matching values and makes sure that this is the same size as the list.
EDIT:
query compile failed because missing the table alias. updated with right table alias.
This is kind of ugly, but it works. On larger datasets I'm not sure what performance would look like, but the nested instances of #GroupValues key off GroupID in the main table so I think as long as you have a good index on GroupID it probably wouldn't be too horrible.
If Object_ID('tempdb..#GroupValues') Is Not Null Drop Table #GroupValues
Create Table #GroupValues (GroupID Int, Val Varchar(10));
Insert #GroupValues (GroupID, Val)
Values (1,'a'),(1,'b'),(1,'c'),(2,'a'),(2,'b'),(3,'a'),(3,'b'),(3,'c'),(3,'d');
If Object_ID('tempdb..#FindValues') Is Not Null Drop Table #FindValues
Create Table #FindValues (Val Varchar(10));
Insert #FindValues (Val)
Values ('a'),('b'),('c');
Select Distinct gv.GroupID
From (Select Distinct GroupID
From #GroupValues) gv
Where Not Exists (Select 1
From #FindValues fv2
Where Not Exists (Select 1
From #GroupValues gv2
Where gv.GroupID = gv2.GroupID
And fv2.Val = gv2.Val))
And Not Exists (Select 1
From #GroupValues gv3
Where gv3.GroupID = gv.GroupID
And Not Exists (Select 1
From #FindValues fv3
Where gv3.Val = fv3.Val))