Basically, what syntex would allow me to achieve the title statement?
If (select statement 1) returns 0 rows THEN (select statement 2) else (select statement 3)
So that the sql returns results from either statement 2 or 3
I've looked for a way to do this but nothing I've found so far seems to exactly address the if requirements.
IF EXISTS (SELECT field FROM table)
BEGIN
SELECT field FROM table2
END
ELSE
BEGIN
SELECT field FROM table3
END
Here you go...
IF ((select count(*) from table1)= 0)
BEGIN
Select * from table2
END
ELSE
BEGIN
SELECT * from table3
END
Sorry for the lack of feedback. Someone else in the office took an interest and came up with this:
select * from (
select *
, (SELECT Count(*)
FROM users
WHERE version_replace = 59 AND moderated = 1) AS Counter
FROM users WHERE version_replace = 59 AND moderated in (0,1)
) AS y
where Counter = 0 and Moderated = 0
or Counter > 0 and Moderated = 1
ORDER By ID DESC
Which does what I need.
Related
Using Sql Server 2012. I have a stored procedure and part of it checks if a username is in a table. If it is, return a 1, if not, return a 2. This is my code:
IF EXISTS (SELECT * FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx') 1 else 2
However, I keep receiving the below error:
Incorrect syntax near '1'.
Is this even possible with an IF EXIST?
Regards,
Michael
If you want to do it this way then this is the syntax you're after;
IF EXISTS (SELECT * FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx')
BEGIN
SELECT 1
END
ELSE
BEGIN
SELECT 2
END
You don't strictly need the BEGIN..END statements but it's probably best to get into that habit from the beginning.
How about using IIF?
SELECT IIF (EXISTS (SELECT 1 FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx'), 1, 2)
Also, if using EXISTS to check the the existence of rows, don't use *, just use 1. I believe it has the least cost.
Its best practice to have TOP 1 1 always.
What if I use SELECT 1 -> If condition matches more than one record then your query will fetch all the columns records and returns 1.
What if I use SELECT TOP 1 1 -> If condition matches more than one record also, it will just fetch the existence of any row (with a self 1-valued column) and returns 1.
IF EXISTS (SELECT TOP 1 1 FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx')
BEGIN
SELECT 1
END
ELSE
BEGIN
SELECT 2
END
In SQL without SELECT you cannot result anything. Instead of IF-ELSE block I prefer to use CASE statement for this
SELECT CASE
WHEN EXISTS (SELECT 1
FROM tblGLUserAccess
WHERE GLUserName = 'xxxxxxxx') THEN 1
ELSE 2
END
You can define a variable #Result to fill your data in it
DECLARE #Result AS INT
IF EXISTS (SELECT * FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx')
SET #Result = 1
else
SET #Result = 2
What the output that you need, select or print or .. so on.
so use the following code:
IF EXISTS (SELECT * FROM tblGLUserAccess WHERE GLUserName ='xxxxxxxx') select 1 else select 2
I have three tables A,B and C. I have to detect if any of them have zero rows. As soon as any table with zero row is detected, I do not need to check other ones.
So, one way is I execute three queries separately and after each query I check the number of returned rows. If its non-zero then only I execute the query of next table.
Second way is I write a single query using case-when, something like
select case
when (select count(*) from A = 0)
then 1
else (
select case
when (select count(*) from B = 0)
then 1
else (
select case
when (select count(*) from B = 0)
then 1
else 0
)
)
end as matchResult;
The second method requires lesser code as I have to write a single query and db will do the comparison for me.
My question is whether its overkilling or can I further optimize the query?
EDIT
On further study, I realise that the query above is wrong. However, I can simply do it as
select case
when (select count(*) from A) = 0 and
(select count(*) from B) = 0 and
(select count(*) from C) = 0
then 1
else 0
end as matchResult;
and if I am not wrong, and conditions are checked from left to right and if any one is false, conditions to the right are not checked.
Please confirm this point.
Count is kind of expensive
select 1
where not exits (select * from a)
or not exits (select * from b)
or not exits (select * from c)
One query with three resutls:
select (select count(*) from A) as Acount,
(select count(*) from B) as Bcount,
(select count(*) from C) as Ccount
This instead gives name of the fitst table that is empty:
select case
when (select count(*) from A)=0 then 'A'
when (select count(*) from B)=0 then 'B'
when (select count(*) from C)=0 then 'C'
else 'ops, all have records' -- remove this to have a null
end as first_empty_table
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
I am using a subquery to return a count as an integer value to my main query. This query is used to rebind an ASP.NET DataGrid and I have only two characters width available for this column. I want to restrict the width to two characters. So, I want to set a value of 99 when the count exceeds 99. I can't figure a way to do this? I can't see how to apply a case statement here.
SELECT
MEMB_ID,
MEMB_Name,
SELECT COUNT(*)
FROM SessionOrder
WHERE SessionOrder.SORD_MEMB_ID = m.MEMB_ID
And SessionOrder.SORD_NumberCompleteDownloads <> 0
As MEMB_Downloads,
MEMB_JoinDate
FROM Member
How can this be done?
Replace
COUNT(*)
With
CASE WHEN COUNT(*) > 99 THEN 99 ELSE COUNT(*) END AS YourColumnName
The CASE expression can look like this:
CASE WHEN COUNT(*) > 99 THEN 99 ELSE COUNT(*) END
There appear to be a couple of errors with your existing query (for example m is not defined). With these errors corrected and the above change made the resulting query could look like this:
SELECT
MEMB_ID,
MEMB_Name,
(
SELECT CASE WHEN COUNT(*) > 99 THEN 99 ELSE COUNT(*) END
FROM SessionOrder
WHERE SessionOrder.SORD_MEMB_ID = MEMB_ID
AND SessionOrder.SORD_NumberCompleteDownloads <> 0
) AS MEMB_Downloads,
MEMB_JoinDate
FROM Member
This might be a bit more efficient. As it can stop scanning rows once the 99th is reached.
SELECT MEMB_ID ,
MEMB_Name,
( SELECT COUNT(*)
FROM (
SELECT TOP 99 *
FROM SessionOrder
WHERE SessionOrder.SORD_MEMB_ID = MEMB_ID
AND SessionOrder.SORD_NumberCompleteDownloads <> 0
)
Top99
) AS MEMB_Downloads,
MEMB_JoinDate
FROM Member
Rather than change the COUNT(*) result, better count at most 99:
SELECT
MEMB_ID,
MEMB_Name,
(SELECT COUNT(*)
FROM (
SELECT TOP(99) *
FROM SessionOrder
WHERE SessionOrder.SORD_MEMB_ID = m.MEMB_ID
And SessionOrder.SORD_NumberCompleteDownloads <> 0)
as TOP99_Downloads)
As MEMB_Downloads,
MEMB_JoinDate
FROM Member;
This way you avoid counting all the downloads when you'll only display 99 anyway. Of course, one would ask what is the point of displaying a value if is incorrect to start with and why not make your UI layer capable of displaying 'more than 99'.
CASE it should be ...
or double UNION as
SELECT
MEMB_ID,
MEMB_Name,
SELECT COUNT(*) AS WC
FROM SessionOrder
WHERE SessionOrder.SORD_MEMB_ID = m.MEMB_ID
And SessionOrder.SORD_NumberCompleteDownloads <> 0
And WC =< 99
As MEMB_Downloads,
MEMB_JoinDate
FROM Member
UNION
SELECT
MEMB_ID,
MEMB_Name,
99 AS WC
FROM SessionOrder
WHERE SessionOrder.SORD_MEMB_ID = m.MEMB_ID
And SessionOrder.SORD_NumberCompleteDownloads <> 0
And WC > 99
As MEMB_Downloads,
MEMB_JoinDate
FROM Member
requestId Consultantid statusid
1 2 10
2 2 10
3 2 10
I want to check if every row has a statusid of 10.
if (every row has a statusid of 10) then
-----do this
endif;
I'm a bit rusty on PL-SQL, but something like this would work in T-SQL:
if not exists (select * from your_table where statusid <> 10) then
-- whatever
end
Edit:
Ok, apparantly in PL-SQL, you need to do something like this:
DECLARE
notallten INTEGER;
BEGIN
SELECT COUNT(*) INTO notallten
FROM your_table
WHERE statusid <> 10
AND ROWNUM = 1;
IF notallten = 0 THEN
-- Do something
END IF;
END;
I don't have an Oracle server to test on though.
declare
v_exists_status_10 number(1);
...
begin
...
-- v_exists_status_10 = 0 if no such row exist, 1 if at least one does
select count(*)
into v_exists_status_10
from dual
where exists
(select * from your_table where statusid <> 10);
if v_exists_status_10 > 0 then
...
Note that you could also do a dumb COUNT() into a variable, but it could be massively inefficient compared to EXISTS. With a COUNT() you'd have to scan all the records, whereas with an EXISTS as soon as it hits a statusid = 10 it can stop scanning.
Simpler solution, that accounts for NULLs in statusid:
for r in (
select 1 dummy
from your_table
where (statusid != 10 or statusid is null)
and rownum = 1) loop
-----do this
end loop;