Please help me to create a select query which contains 10 'where' clause and the order should be like that:
the results should be displayed in order of most keywords(where conditions) matched down to least matched.
NOTE: all 10 condition are with "OR".
Please help me to create this query.
i am using ms-sql server 2005
Like:
Select *
from employee
where empid in (1,2,4,332,434)
or empname like 'raj%'
or city = 'jodhpur'
or salary >5000
In above query all those record which matches maximum conditions should be on top and less matching condition record should be at bottom.
SELECT *
FROM (SELECT (CASE WHEN cond1 THEN 1 ELSE 0 END +
CASE WHEN cond2 THEN 1 ELSE 0 END +
CASE WHEN cond2 THEN 1 ELSE 0 END +
...
CASE WHEN cond10 THEN 1 ELSE 0 END
) AS numMatches,
other_columns...
FROM mytable
) xxx
WHERE numMatches > 0
ORDER BY numMatches DESC
EDIT: This answer was posted before the question was modified with a concrete example. Marcelo's solution addresses the actual problem. On the other hand, my answer was giving priority to matches of specific fields.
You may want to try something like the following, using the same expressions in the ORDER BY clause as in your WHERE clause:
SELECT *
FROM your_table
WHERE field_1 = 100 OR
field_2 = 200 OR
field_3 = 300
ORDER BY field_1 = 100 DESC,
field_2 = 200 DESC,
field_3 = 300 DESC;
I've recently answered a similar question on Stack Overflow which you might be interested in checking out:
Is there a SQL technique for ordering by matching multiple criteria?
There are many options/answers possible. Best answer depends on size of the data, non-functional requirements, etc.
That said, what I would do is something like this (easy to read / debug):
Select * from
(Select *, iif(condition1 = bla, 1, 0) as match1, ..... , match1+match2...+match10 as totalmatchscore from sourcetable
where
condition1 = bla or
condition2 = bla2
....) as helperquery
order by helperquery.totalmatchscore desc
I could not get this to work for me on Oracle.
If using oracle, then this Order by Maximum condition match is a good solution.
Utilizes the case when language feature
Related
I have the following query. I simplified it for demo purpose. I am using SQL Server - t-sql
Select tm.LocID = (select LocID from tblLoc tl
where tl.LocID = tm.LodID )
from tblMain tm
if the subquery returns multiple records, I like to assign tm.LocID to null else if there is only 1 record returned then assign it to tm.LocID. I am looking for a simple way to do this. Any help would be appreciated.
One way I can see is to have a CASE statement and check if (Count * > 1 ) then assign null else return the value but that would require a select statement within a select statement.
You have the right idea about using a case expression for count(*), but it will not require another subquery:
SELECT tm.LocID = (SELECT CASE COUNT(*) WHEN 1 THEN MAX(LocID) END
FROM tblLoc tl
WHERE tl.LocID = tm.LodID )
FROM tblMain tm
or just use a HAVING clause, like
Select tm.LocID = (select LocID from tblLoc tl
where tl.LocID = tm.LodID
group by locID
having count(*) = 1)
)
from tblMain tm
Your query above (and many of the other answers here) is a correlated subquery which will be very slow since it performs a separate aggregation query on each record. This following will address both your problem and potentially perform a bit better since the count happens in a single pass.
SELECT
CASE
WHEN x.locid IS NOT NULL THEN x.locid
ELSE NULL
END
FROM tblMain m
LEFT JOIN (
SELECT
locid
FROM tblLoc
GROUP BY locid
HAVING COUNT(1) = 1
) x
ON x.locid = m.locid
;
The above is in Postgres syntax (what I'm familiar with) so you would have to make it TSQL compatible.
I have a weird scenario, in which I need to keep all the rows at top in which X column has NULL value else sort by Y column. Can you help me in writing query.
ORDER BY CASE WHEN X IS NULL THEN 0 ELSE 1 END, Y
You can use a CASE statement in ORDER BY:
ORDER BY
CASE WHEN X IS NULL THEN 0 ELSE 1 END ASC, Y
Here you go, this will work with any sql platform -- for a specific platform there might be a better way to do it.
SELECT * FROM
(
SELECT 1 AS orderC, *
FROM tableName
WHERE Xcolumn is null
UNION ALL
SELECT 2 AS orderC, *
FROM tableName
WHERE Xcolumn is not null
)
ORDER BY orderC ASC, columnY
Note, if you don't want orderC to be in the output, just specify all the other columns in the outer select.
Sharing what I learned before using:
ORDER BY FIELD(Xcolumn, NULL) DESC, Ycolumn DESC
SELECT * FROM TABLENAME ORDER BY X ,Y
You can use query like below:
SELECT * FROM Emp WHERE empId= 6 AND DELETED = 0
ORDER BY CASE WHEN DOB IS NULL THEN 0 ELSE 1 END
, CREATETIMESTAMP.
for more details you can see here
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.
How can the below query be adjusted to return always the member with MemberID = 'xxx' as the first row
SELECT * FROM Members
select * from Members
order by case when MemberID = XXX then 0 else 1 end
This should work and it will also allow you to order the remaining items by MemberID (Assuming xxx=12 in this example)
SELECT *
FROM Members
ORDER BY CASE WHEN MemberID=12 THEN NULL ELSE isnull(MemberID,0) END
If the memberID column can't contain nulls, you can get away with this which might perform slightly better.
SELECT *
FROM Members
ORDER BY CASE WHEN MemberID=12 THEN NULL ELSE MemberID END
SELECT
CASE WHEN MemberID = 'xxx' AS 1 ELSE 0 END CASE AS magic,
*
FROM Members
ORDER BY magic DESC
The syntax might vary depending on yr db, but I hope you get the idea.
SELECT * FROM `Members` WHERE `MemberID` = '[ID]' LIMIT 1 UNION SELECT * FROM `Members`
This should work. Tested on my database instance. Chosen ID is always first.
A more robust solution, if you have more than one record that has to be floated to the top, or if you have a specific order for multiple records, is to add a ResultsOrder column to your table, or even another table MemberOrder(memberid, resultorder). Fill resultorder with big numbers and ...
Select m.*
From Members m
Left Join MemberOrder mo on m.MemberID=mo.MemberID
Order by coalesce(mo.resultorder, 0) DESC
try this:
SELECT * FROM Members
ORDER BY IF(x.MemberId = XXX, -1, ABS(x.MemberId))
We've got some SQL code I'm trying to optimize. In the code is a view that is rather expensive to run. For the sake of this question, let's call it ExpensiveView. On top of the view there is a query that joins the view to itself via a two sub-queries.
For example:
select v1.varCharCol1, v1.intCol, v2.intCol from (
select someId, varCharCol1, intCol from ExpensiveView where rank=1
) as v1 inner join (
select someId, intCol from ExpensiveView where rank=2
) as v2 on v1.someId = v2.someId
An example result set:
some random string, 5, 10
other random string, 15, 15
This works, but it's slow since I'm having to select from ExpensiveView twice. What I'd like to do is use a case statement to only select from ExpensiveView once.
For example:
select someId,
case when rank = 1 then intCol else 0 end as rank1IntCol,
case when rank = 2 then intCol else 0 end as rank2IntCol
from ExpensiveView where rank in (1,2)
I could then group the above results by someId and get almost the same thing as the first query:
select sum(rank1IntCol), sum(rank2Intcol)
from ( *the above query* ) SubQueryData
group by someId
The problem is the varCharCol1 that I need to get when the rank is 1. I can't use it in the group since that column will contain different values when rank is 1 than it does when rank is 2.
Does anyone have any solutions to optimize the query so it only selects from ExpensiveView once and still is able to get the varchar data?
Thanks in advance.
It's hard to guess since we don't see your view definition, but try this:
SELECT MIN(CASE rank WHEN 1 THEN v1.varCharCol1 ELSE NULL END),
SUM(CASE rank WHEN 1 THEN rank1IntCol ELSE 0 END),
SUM(CASE rank WHEN 2 THEN rank2IntCol ELSE 0 END)
FROM query
GROUP BY
someId
Note that in most cases for the queries like this:
SELECT *
FROM mytable1 m1
JOIN mytable1 m2
ON …
the SQL Server optimizer will just build an Eager Spool (a temporary index), which will later be used for searching for the JOIN condition, so probably these tricks are redundant.
select someId,
case when rank = 1 then varCharCol1 else '_' as varCharCol1
case when rank = 1 then intCol else 0 end as rank1IntCol,
case when rank = 2 then intCol else 0 end as rank2IntCol
from ExpensiveView where rank in (1,2)
then use min() or max in the enclosing query