How to select an empty result set?
There's a dummy-table in MySQL called 'dual', which you should be able to use.
select
1
from
dual
where
false
This will always give you an empty result.
How do I return an empty result set from a procedure using T-SQL?
If you want to simply retrieve the metadata of a result set w/o any actual row, use SET FMTONLY ON
.
Simple select query returning empty result set?
You need backquotes instead of single quotes. Try:
SELECT * FROM `votes` WHERE `user_id` = 8 AND `image_id` = 5;
Single quotes are used for string constants. So the string "user_id" is not equal to the integer "8".
How to get empty result set with a CASE statement?
You can filter out NULL
values in the outer WHERE
clause.
SELECT CASE WHEN ('test' IS NULL) THEN (SELECT 'null_result') ELSE (SELECT 'empty_result' WHERE 1<>1) END
WHERE CASE WHEN ('test' IS NULL) THEN (SELECT 'null_result') ELSE (SELECT 'empty_result' WHERE 1<>1) END IS NOT NULL;
or
SELECT *
FROM (
SELECT CASE WHEN ('test' IS NULL) THEN (SELECT 'null_result') ELSE (SELECT 'empty_result' WHERE 1<>1) END as result_case
) x
WHERE result_case IS NOT NULL;
How to get empty result set in MySQL query with aggregate function?
- To consider all of the "riders", despite having no distance travelled, you need to use
Left Join
with thedriver
table as your first table. - Now, to calculate the total distance travelled by them, use Sum() with Ifnull() function to return 0 distance travelled instead of
null
. Due to left join, distance value will come up asnull
if there is no matching row found in the second tableride
. - Also, you should use
Group By
when using aggregate functions likeSum
.
Try the following:
select d.name as 'name',
sum(ifnull(r.distance,0)) as 'sum_distance'
from driver d
left join ride r on r.driver_id = d.id
where r.end_time2 > '2018-09-25'
and r.start_time2 < '2018-09-26'
group By d.name
How to return empty result for columns in a stored procedure
You can apply a trick like below-
DECLARE @RunDate date = '20190504'
IF DATENAME(WEEKDAY, @RunDate) NOT IN ('Saturday','Sunday')
BEGIN
--Do the actual Logic
--For Example
SELECT * FROM your_table
END
ELSE
BEGIN
--Do the tricks
SELECT * FROM your_table
WHERE 1= 2 -- This will never return a row!! But the column names :)
END
Simple check for SELECT query empty result
Use @@ROWCOUNT:
SELECT * FROM service s WHERE s.service_id = ?;
IF @@ROWCOUNT > 0
-- do stuff here.....
According to SQL Server Books Online:
Returns the number of rows affected by
the last statement. If the number of
rows is more than 2 billion, use
ROWCOUNT_BIG.
How to check result set is empty in store procedure
You can use an IF NOT EXISTS
:
IF NOT EXISTS (SELECT xmlRequest FROM Api_request
WHERE Api_id = @Api_id)
BEGIN
/*if result set empty*/
/* will add some logic here */
END
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