I want to return 0 if there is no record or if the Column1 is null.
select #var = Column1
from myschema.mytable
where Id = #suppliedId;
select isnull(#var, 0);
The above code outputs 0 if if Column1 is null. Or if a row is not found
Whereas I tried to save some keystrokes but it resulted in,
select isnull(Column1, 0)
from myschema.mytable
where Id = #suppliedId;
The above code outputs null if Column1 is null or when there is no row
Any ideas what is wrong here ? Or is there any shorter way of writing the first code ?
You can do
SELECT #var = ISNULL(MAX(Column1), 0)
FROM myschema.mytable
WHERE Id = #suppliedId;
A scalar aggregate always returns a single row even if the underlying query returns zero rows.
Not really saving key strokes, but something like this could help :-)
SELECT TOP 1 tbl.field
FROM
(
SELECT 0 AS inx, 'no record' AS field
--if only one row is possible, than set '1' literally
UNION SELECT ROW_NUMBER() OVER(ORDER BY mytable.orderfield), ISNULL(mytable.Land,'is null')
FROM mytable
WHERE IDENTITY = #suppliedID
) AS tbl
ORDER BY tbl.inx DESC
Related
I want to be able to check if we have a column and if not, then we just want to add an empty column,
IF Users.[parties] = '' OR NULL
BEGIN
SELECT [parties]
FROM Users
UNION
SELECT 'Empty'
END
The Users.[parties], we check to see if we have a column but if we don't, it will result in a crash, in the case for this event I thought it would be best just to add an empty column with the name of Empty but I can't get the code to work above.
If we do have columns, the results will be something like...
ColumnsName ColumnAge
data 33
data 22
But when there isn't a column, it crashes and ideally I would like it to just have an empty column like this,
EmptyColumn
The code below checks whether a column exists in the table, in our case the name of the column is columnName and the name of the table is tableName.
IF COL_LENGTH('schemaName.tableName', 'columnName') IS NOT NULL
BEGIN
-- Column exists
SELECT [parties] FROM Users
END
ELSE
BEGIN
-- Column does not exists
SELECT 'Empty'[parties]
END
I think you just want
IF EXISTS(
SELECT 1
FROM Sys.Columns
WHERE Name = N'parties'
AND
Object_ID = Object_ID(N'SchemaName.Users')
)
BEGIN
SELECT parties
FROM Users;
END
ELSE
BEGIN
SELECT 'EmptyColumn' EmptyColumn -- or NULL EmptyColumn
FROM Users;
END
I'll try with this: (I'm not sure it works)
select case when ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) =0 --count rows
then 'empty' -- if 0 output empty
else parties end as parties --else ouputs the result
from your_table
This is a more 'standard' approach
CREATE VIEW user_filled as
SELECT [parties]
FROM Users
UNION
SELECT 'EMPTY'
and when you query it (if needed -> on count(*))
select count(*)
from user_filled
where parties <> 'EMPTY'
on join
select *
from user_filled join other_table
on (user_filled <> 'EMPTY and userfilled.key= other_table.key)
NOTE: put the clause into the ON so it's filtered out BEFORE the join is made
What is better approach to check existence of an object in database?
select count(id) as count from my_table where name="searchedName";
OR
select id from my_table where name="searchedName";
And then check if count > 0 or the object is not null (ORM logic)
EDIT:
select id to be valid for Oracle.
The idea should be to that we only need to find one record in order to say that such record exists. This can be done with an EXISTS clause in standard SQL.
select exists (select * from mytable where name = 'searchedName');
returns true if the table contains a record with 'searchedName' and false otherwise.
If you want 0 for false and 1 for true instead (e.g. if the DBMS does not support booleans):
select case when exists (select * from mytable where name = 'searchedName')
then 1 else 0 end as does_exist;
You say you want this for Oracle. In Oracle you can use above query, but you'd have to select from the table dual:
select case when exists (select * from mytable where name = 'searchedName')
then 1 else 0 end as does_exist
from dual;
But for Oracle we'd usually use rownum instead:
select count(*) as does_exist
from mytable
where name = 'searchedName'
and rownum = 1; -- to find one record suffices and we'd stop then
This also returns 1 if the table contains a record with 'searchedName' and 0 otherwise. This is a very typical way in Oracle to limit lookups and the query is very readable (in my opinion).
I'd just call:
select id from my_table where name='searchedName';
Making sure there is an index for the name column.
And then check whether or not the result is empty.
Try with IF EXISTS (
if exists (select 1 from my_table where name = "searchedName")
begin
....
end
I have a query inside a stored procedure that sums some values inside a table:
SELECT SUM(columnA) FROM my_table WHERE columnB = 1 INTO res;
After this select I subtract res value with an integer retrieved by another query and return the result. If WHERE clause is verified, all works fine. But if it's not, all my function returns is an empty column (maybe because I try to subtract a integer with an empty value).
How can I make my query return zero if the WHERE clause is not satisfied?
You could:
SELECT COALESCE(SUM(columnA), 0) FROM my_table WHERE columnB = 1
INTO res;
This happens to work, because your query has an aggregate function and consequently always returns a row, even if nothing is found in the underlying table.
Plain queries without aggregate would return no row in such a case. COALESCE would never be called and couldn't save you. While dealing with a single column we can wrap the whole query instead:
SELECT COALESCE( (SELECT columnA FROM my_table WHERE ID = 1), 0)
INTO res;
Works for your original query as well:
SELECT COALESCE( (SELECT SUM(columnA) FROM my_table WHERE columnB = 1), 0)
INTO res;
More about COALESCE() in the manual.
More about aggregate functions in the manual.
More alternatives in this later post:
How to return a value from a function if no value is found
I'm not familiar with postgresql, but in SQL Server or Oracle, using a subquery would work like below (in Oracle, the SELECT 0 would be SELECT 0 FROM DUAL)
SELECT SUM(sub.value)
FROM
(
SELECT SUM(columnA) as value FROM my_table
WHERE columnB = 1
UNION
SELECT 0 as value
) sub
Maybe this would work for postgresql too?
You can also try: (I tried this and it worked for me)
SELECT ISNULL((SELECT SUM(columnA) FROM my_table WHERE columnB = 1),0)) INTO res;
You can use exists clause.
IF EXISTS(SELECT FROM my_table WHERE columnB = 1)
THEN
res := SUM(columnA);
ELSE
res := 0
END IF;
I am constructing an SQL statement with some parameters. Finally, an SQL statement is created like
"select * from table where column1 = "xyz"".
But I also need the rows which are filtered with this statement. In this case they're rows which are not "xyz" valued in column1. More specifically, I am looking for something like INVERSE(select * from table where ...). Is it possible?
Edit: My bad, I know I can do it with != or operator. Here the case is, select statement may be more complex (with some ANDs and equal, greater operators). Let's assume a table has A,B,C and my SQL statement brings only A as result. But I need B and C while I only have the statement which brings A.
select * from table where column1 != 'xyz' or column1 is null;
If you want the other ones, do it like this:
select * from table where column1 <> "xyz"
column1 <> (differs from) "xyz"
To check if something is no equal you can use <> or even !=
SELECT *
FROM yourTable
WHERE <> 'xyz'
OR
SELECT *
FROM yourTable
WHERE != 'xyz'
Many database vendors support (see list) both versions of the syntax.
If you're retrieving both result sets at about the same time, and just want to process the xyz ones first, you could do:
select *,CASE WHEN column1 = "xyz" THEN 1 ELSE 0 END as xyz from table
order by CASE WHEN column1 = "xyz" THEN 1 ELSE 0 END desc
This will return all of the rows in one result set. Whilst xyz = 1, these were the rows with column1 = 'xyz'.
It was :
"select * from table where rowId NOT IN (select rowId from table where column1 = "xyz")
I needed a unique rowId column to achieve this.
I want to return multiple values from a query in oracle. For ex:
select count(*)
from tablename a
where asofdate='10-nov-2009'
and a.FILENAME in (case
when 1 = 1 then (select distinct filename from tablename
where asofdate='10-nov-2009' and isin is null)
else null
end);
I am getting error: ora 01427 single row subquery returns more than one row
Please advice.
Thanks, Deepak
A CASE statement cannot return more than one value, it is a function working on one value.
It is not required for your statement, this statement should work:
select count(*)
from tablename a
where asofdate='10-nov-2009'
and a.FILENAME in (select distinct filename
from tablename
where asofdate='10-nov-2009'
and isin is null);
Maybe you have another usage scenario in mind? Something like this:
Select *
From aTable
Where in CASE
WHEN Then
WHEN Then
ELSE END
Then using CASE may not be the right scenario. Maybe this helps you in the right direction:
Select *
From aTable
Where <Case1> and column1 in <Subselect1>
Or <Case2> and column1 in <Subselect2>
OR Not (<Case1> Or <Case2>) and column1 in <Subselect3>
But this will probably be quite some work for the optimizer ...
The distinct in your Case statement is attempting to return multiple values when only one is allowed, and your SELECT statement will only return one value in one row currently. If you're trying to get the count of each filename, do
SELECT FileName, Count(*)
FROM tablename
WHERE asofdate='10-nov-2009' and isin is null
GROUP BY FileName
Run this query:
select distinct filename from tablename
where asofdate='10-nov-2009' and isin is null
You'll see that it returns more than a single row which causes the ORA-01427.
For all I can tell, you're looking for something like:
select a.filename, count(*)
from tablename a
where a.asofdate = '10-nov-2009'
and exists (
select *
from tablename b
where b.isin is null
and a.asofdate = '10-nov-2009'
and a.filename = b.filename
)
group by a.filename
This would find the count of filenames for a day, for which there exists at least one row where isin is null.
If you edit your question and add an explanation of what you're looking for, you might get better answers.