I have two tables:
ASSIGNMENTS (ID)
ASSIGNMENT_REVIEWS (ID, ASSIGNMENT_ID)
As a result of selecting I'd like to retrieve a flag if a review is already presented for the assignment. How to do it in the best way?
You are looking for the exists statement:
select
id,
case when exists (
select 1 from assignment_reviews where assignment_reviews.assignment_id = assignments.id
) then 1 else 0 end as hasReview
from
assignments
You can use a left join with nvl2() function(returns the
value in the 2nd argument if the 1st argument is not null, otherwise
returns the 3rd argument practically )
with assignments(id) as
(
select 101 from dual union all
select 102 from dual
), assignments_reviews(id,assignment_id) as
(
select 855, 101 from dual
)
select a.id,
nvl2(r.assignment_id,1,0) as already_presented
from assignments a
left join assignments_reviews r
on r.assignment_id = a.id;
ID ALREADY_PRESENTED
101 1
102 0
Demo
Related
I am searching with a query
--Code Format
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3);
If MYTABLE does not contain rows with SWITCH 1,2 or 3 I need default values returned along with the SWITCH value. How do I do it?
Below is my table format
COLA | COLB | COLC | SWITCH
------------------------------
A B C 1
a b c 2
i want a query when I search with
select * from MYTABLE where switch in (1,2,3)
That gets results like this --
COLA | COLB | COLC | SWITCH
------------------------------
A B C 1
a b c 2
NA NA NA 3
--Check to see if any row exists matching your conditions
IF NOT EXISTS (SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3))
BEGIN
--Select your default values
END
ELSE
BEGIN
--Found rows, return them
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3)
END
if not exists( SELECT 1 from MYTABLE where SWITCH IN (1,2,3))
select default_value
How about:
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3)
union select 5555, 6666, 7777 where not exists (
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3)
);
5555, 6666, 7777 being the default row in case there aren't any rows matching your criteria.
Here is one way to tackle this. You need a table of the SWITCH values you want to look at. Then a simple left join makes this super easy.
select ColA
, ColB
, ColC
v.Switch
from
(
values
(1)
, (2)
, (3)
)v (Switch)
left join YourTable yt on yt.Switch = v.Switch
You can Use a Split Function And Left Join As Shown Below:
Select ISNULL(ColA,'NA') As ColA,ISNULL(ColB,'NA') As ColB,ISNULL(ColC,'NA') As ColC,ISNULL(Switch,a.splitdata)
from [dbo].[fnSplitString]('1,2,3',',') a
LEFT JOIN #MYTABLE t on a.splitdata=t.Switch
[dbo].[fnSplitString] is a Split Function with 2 arguments - Delimeter Separated String and Delimeter and Output a Table.
EDIT:
Given the new explanation, I changed the answer completely. I think I got your question now:
SELECT * FROM MYTABLE AS mt
RIGHT JOIN (SELECT 1 AS s UNION SELECT 2 AS s UNION SELECT 3 AS s) AS st
ON st.s = mt.SWITCH
You could change the SELECT 1 AS s UNION SELECT 2 AS s UNION SELECT 3 AS spart to a subquery that results in all possible values SWITCH could assume. E.g.:
SELECT DISTINCT SWITCH FROM another_table_with_all_switches
If all want is the value of switch that is not in MYTABLE, not the whole table with null values, you could try:
SELECT * FROM
(SELECT 1 AS s UNION SELECT 2 AS s UNION SELECT 3) AS st
WHERE st.s NOT IN (SELECT DISTINCT SWITCH FROM MYTABLE)
Suppose I have a list of values, such as 1, 2, 3, 4, 5 and a table where some of those values exist in some column. Here is an example:
id name
1 Alice
3 Cindy
5 Elmore
6 Felix
I want to create a SELECT statement that will include all of the values from my list as well as the information from those rows that match the values, i.e., perform a LEFT OUTER JOIN between my list and the table, so the result would be like follows:
id name
1 Alice
2 (null)
3 Cindy
4 (null)
5 Elmore
How do I do that without creating a temp table or using multiple UNION operators?
If in Microsoft SQL Server 2008 or later, then you can use Table Value Constructor
Select v.valueId, m.name
From (values (1), (2), (3), (4), (5)) v(valueId)
left Join otherTable m
on m.id = v.valueId
Postgres also has this construction VALUES Lists:
SELECT * FROM (VALUES (1, 'one'), (2, 'two'), (3, 'three')) AS t (num,letter)
Also note the possible Common Table Expression syntax which can be handy to make joins:
WITH my_values(num, str) AS (
VALUES (1, 'one'), (2, 'two'), (3, 'three')
)
SELECT num, txt FROM my_values
With Oracle it's possible, though heavier From ASK TOM:
with id_list as (
select 10 id from dual union all
select 20 id from dual union all
select 25 id from dual union all
select 70 id from dual union all
select 90 id from dual
)
select * from id_list;
the following solution for oracle is adopted from this source. the basic idea is to exploit oracle's hierarchical queries. you have to specify a maximum length of the list (100 in the sample query below).
select d.lstid
, t.name
from (
select substr(
csv
, instr(csv,',',1,lev) + 1
, instr(csv,',',1,lev+1 )-instr(csv,',',1,lev)-1
) lstid
from (select ','||'1,2,3,4,5'||',' csv from dual)
, (select level lev from dual connect by level <= 100)
where lev <= length(csv)-length(replace(csv,','))-1
) d
left join test t on ( d.lstid = t.id )
;
check out this sql fiddle to see it work.
Bit late on this, but for Oracle you could do something like this to get a table of values:
SELECT rownum + 5 /*start*/ - 1 as myval
FROM dual
CONNECT BY LEVEL <= 100 /*end*/ - 5 /*start*/ + 1
... And then join that to your table:
SELECT *
FROM
(SELECT rownum + 1 /*start*/ - 1 myval
FROM dual
CONNECT BY LEVEL <= 5 /*end*/ - 1 /*start*/ + 1) mypseudotable
left outer join myothertable
on mypseudotable.myval = myothertable.correspondingval
Assuming myTable is the name of your table, following code should work.
;with x as
(
select top (select max(id) from [myTable]) number from [master]..spt_values
),
y as
(select row_number() over (order by x.number) as id
from x)
select y.id, t.name
from y left join myTable as t
on y.id = t.id;
Caution: This is SQL Server implementation.
fiddle
For getting sequential numbers as required for part of output (This method eliminates values to type for n numbers):
declare #site as int
set #site = 1
while #site<=200
begin
insert into ##table
values (#site)
set #site=#site+1
end
Final output[post above step]:
select * from ##table
select v.id,m.name from ##table as v
left outer join [source_table] m
on m.id=v.id
Suppose your table that has values 1,2,3,4,5 is named list_of_values, and suppose the table that contain some values but has the name column as some_values, you can do:
SELECT B.id,A.name
FROM [list_of_values] AS B
LEFT JOIN [some_values] AS A
ON B.ID = A.ID
Oracle11g
I want to know if a player has ever played shortstop. However, a player
may not even be in my table, yet I'd still like to return a row for that player. In this case, player #3 is not in table, but I'd like to return a row nevertheless.
Selection Criteria
If player has at least one SHORTSTOP record then return just 1 row with YES.
If player has at least one record and none of them are SHORTSTOP then return just one row with NO.
If player has no records then return just one row with NO.
Query
with baseball_players as
(select 1 as player_id, 'SHORTSTOP' as position from dual union all
select 1 as player_id, 'FIRSTBASE' as position from dual union all
select 2 as player_id, 'FIRSTBASE' as position from dual)
select player_id, case position
when 'SHORTSTOP' then 'YES'
else 'NO'
end has_played
from baseball_players
where player_id in (1,2,3)
Question: How can I write query to get desired results?
Desired Output
PLAYER_ID HAS_PLAYED
----------------------
1 YES
2 NO
3 NO
How about this:
WITH playerList AS
(
SELECT
1 player_id
FROM
dual
UNION
SELECT
2
FROM
dual
UNION
SELECT
3
FROM
dual
)
, baseball_players as
(
select 1 as player_id, 'SHORTSTOP' as position from dual union all
select 1 as player_id, 'FIRSTBASE' as position from dual union all
select 2 as player_id, 'FIRSTBASE' as position from dual
)
SELECT
pl.player_id
, MAX(CASE WHEN bp.position = 'SHORTSTOP' THEN 'YES' ELSE 'NO' END)
FROM
playerList pl
LEFT JOIN
baseball_players bp
ON
bp.player_id = pl.player_id
GROUP BY
pl.player_id
Rather than using a where clause, create a tempoary table, insert the values in and left join on the table you created.
Use a case statement for IF NULL then NO, otherwise YES.
Suppose I have a table with columns user_id, name and the table contains data like this:
user_id name
------- -----
sou souhardya
cha chanchal
swa swapan
ari arindam
ran ranadeep
If I want to know these users (sou, cha, ana, agn, swa) exists in this table or not then I want output like this:
user_id it exists or not
------- -----------------
sou y
cha y
ana n
agn n
swa y
As ana and aga do not exist in the table it must show "n" (like the above output).
Assuming your existing checklist is not on the database, you will have to assemble a query containing those. There are many ways of doing it. Using CTEs, it would look like this:
with cte as
(
select 'sou' user_id
union all
select 'cha'
union all
select 'ana'
union all
select 'agn'
union all
select 'swa'
)
select
cte.user_id,
case when yt.user_id is null then 'n' else 'y' end
from cte
left join YourTable yt on cte.user_id = yt.user_id
This also assumes user_id is unique.
Here is the SQLFiddle with the proof of concept: http://sqlfiddle.com/#!3/e023a0/4
Assuming you're just testing this manually:
DECLARE #Users TABLE
(
[user_id] VARCHAR(50)
)
INSERT INTO #Users
SELECT 'sou'
UNION SELECT 'cha'
UNION SELECT 'ana'
UNION SELECT 'agn'
UNION SELECT 'swa'
SELECT a.[user_id]
, [name]
, CASE
WHEN b.[user_id] IS NULL THEN 'N'
ELSE 'Y'
END AS [exists_or_not]
FROM [your_table] a
LEFT JOIN #Users b
ON a.[user_id] = b.[user_id]
You didn't provide quite enough information to provide a working example, but this should get you close:
select tbl1.user_id, case tbl2.user_id is null then 'n' else 'y' end
from tbl1 left outer join tbl2 on tbl1.user_id = tbl2.user_id
;with usersToCheck as
(
select 'sou' as userid
union select 'cha'
union select 'ana'
union select 'agn'
union select 'swa'
)
select utc.userid,
(case when exists ( select * from usersTable as ut where ut.user_id = utc.userid) then 'y' else 'n' end)
from usersToCheck as utc
Let's say I have an sql server table:
NumberTaken CompanyName
2 Fred 3 Fred 4 Fred 6 Fred 7 Fred 8 Fred 11 Fred
I need an efficient way to pass in a parameter [StartingNumber] and to count from [StartingNumber] sequentially until I find a number that is missing.
For example notice that 1, 5, 9 and 10 are missing from the table.
If I supplied the parameter [StartingNumber] = 1, it would check to see if 1 exists, if it does it would check to see if 2 exists and so on and so forth so 1 would be returned here.
If [StartNumber] = 6 the function would return 9.
In c# pseudo code it would basically be:
int ctr = [StartingNumber]
while([SELECT NumberTaken FROM tblNumbers Where NumberTaken = ctr] != null)
ctr++;
return ctr;
The problem with that code is that is seems really inefficient if there are thousands of numbers in the table. Also, I can write it in c# code or in a stored procedure whichever is more efficient.
Thanks for the help
A solution using JOIN:
select min(r1.NumberTaken) + 1
from MyTable r1
left outer join MyTable r2 on r2.NumberTaken = r1.NumberTaken + 1
where r1.NumberTaken >= 1 --your starting number
and r2.NumberTaken is null
I called my table Blank, and used the following:
declare #StartOffset int = 2
; With Missing as (
select #StartOffset as N where not exists(select * from Blank where ID = #StartOffset)
), Sequence as (
select #StartOffset as N from Blank where ID = #StartOffset
union all
select b.ID from Blank b inner join Sequence s on b.ID = s.N + 1
)
select COALESCE((select N from Missing),(select MAX(N)+1 from Sequence))
You basically have two cases - either your starting value is missing (so the Missing CTE will contain one row), or it's present, so you count forwards using a recursive CTE (Sequence), and take the max from that and add 1
Edit from comment. Yes, create another CTE at the top that has your filter criteria, then use that in the rest of the query:
declare #StartOffset int = 2
; With BlankFilters as (
select ID from Blank where hasEntered <> 1
), Missing as (
select #StartOffset as N where not exists(select * from BlankFilters where ID = #StartOffset)
), Sequence as (
select #StartOffset as N from BlankFilters where ID = #StartOffset
union all
select b.ID from BlankFilters b inner join Sequence s on b.ID = s.N + 1
)
select COALESCE((select N from Missing),(select MAX(N)+1 from Sequence))
this may now return a row that does exist in the table, but hasEntered=1
Tables:
create table Blank (
ID int not null,
Name varchar(20) not null
)
insert into Blank(ID,Name)
select 2 ,'Fred' union all
select 3 ,'Fred' union all
select 4 ,'Fred' union all
select 6 ,'Fred' union all
select 7 ,'Fred' union all
select 8 ,'Fred' union all
select 11 ,'Fred'
go
Try the set based approach - should be faster
select min(t1.NumberTaken)+1 as "min_missing" from t t1
where not exists (select 1 from t t2
where t1.NumberTaken = t2.NumberTaken+1)
and t1.NumberTaken > #StartingNumber
This is Sybase syntax, so massage for SQL server consumption if needed.
Create a temp table with all numbers from StartingValue to EndValue and LEFT OUTER JOIN to your data table.