I'm new to SQL and I'm wondering how to pivot a table like:
Col1 Col2 Col3
1 a w
2 a x
1 b y
2 b z
Into
Col1 a b
1 w y
2 x z
I was playing with GROUP BY but I can't seem to be able to turn unique rows into columns
This can be done using an aggregate function with a CASE expression:
select col1,
max(case when col2 = 'a' then col3 end) a,
max(case when col2 = 'b' then col3 end) b
from yourtable
group by col1
See SQL Fiddle with Demo
If you are using an RDBMS with a PIVOT function (SQL Server 2005+ / Oracle 11g+), then your query would be similar to this (Note: Oracle syntax below):
select *
from
(
select col1, col2, col3
from yourtable
)
pivot
(
max(col3)
for col2 in ('a', 'b')
)
See SQL Fiddle with Demo
The last way that you can do this is by using multiple joins on the same table:
select t1.col1,
t1.col3 a,
t2.col3 b
from yourtable t1
left join yourtable t2
on t1.col1 = t2.col1
and t2.col2 = 'b'
where t1.col2 = 'a'
See SQL Fiddle with Demo
All give the result:
| COL1 | 'A' | 'B' |
--------------------
| 1 | w | y |
| 2 | x | z |
If you require that the distinct values in Col2 can change without forcing changes on your query definition, you may be looking for an OLAP structure like SQL Analysis Services.
You should try something like
select * from
(select Col1, Col2, Col3 from TableName)
pivot xml (max(Col3)
for Col2 in (any) )
I'm on a mobile so I can't test if it's working right now.
Related
I have some data that looks like this:
col1, col2, col3
A, 1.2, A|X|Y|Z
B, 0.3, B|X|Y|Z
X, 1.0, X|Y|Z
Y, 0.2, Y|Z
Z, 1.0, Z
I want to select the rows where the item in col1 appears in the col3 pipe-delimited list other than its own list. And for each of those items, I want to count the number of rows where that item appears in col3, and also sum col2 where that condition is met. So the results should be something like this:
col1, foo, bar
X, 2, 1.5
Y, 3, 2.5
Z, 4, 2.7
I've been trying to use CASE WHEN and LIKE to do this (see below), but it's not working. For foo I get all zeroes, and for bar I get null. Maybe I need some kind of subquery that I don't understand how to use?
SELECT
col1,
COUNT(CASE WHEN col3 LIKE col1 THEN 1 END) as foo,
SUM(CASE WHEN col3 LIKE col1 THEN col2 END) as bar
FROM table
GROUP BY
col1
You can do this with a self-join. In standard SQL, it would look like:
select t.col1, count(*) as foo, sum(col2) as bar
from t join
t t2
on '|' || t2.col3 || '|' like '%|' || t.col1 || '|%'
group by t.col1;
The syntax might vary in the database you are actually using, but the idea should work with whatever string concatenation mechanism your database uses.
With a self join and aggregation:
SELECT t1.col1, COUNT(*) foo, SUM(t2.col2) bar
FROM tablename t1 INNER JOIN tablename t2
ON t2.col1 <> t1.col1 AND CONCAT('|', t2.col3, '|') LIKE CONCAT('%|', t1.col1, '|%')
GROUP BY t1.col1
The above code will work in MySql.
For other databases you can use their concatenation operators like || or +.
See the demo.
Results:
> col1 | foo | bar
> :--- | --: | --:
> X | 2 | 1.5
> Y | 3 | 2.5
> Z | 4 | 2.7
I would like to get the data from previous row. I have used LAG function but did not get the expected result.
Table:-
col1 col2 col3
ABCD 1 Y
ABCD 2 N
ABCD 3 N
EFGH 4 N
EFGH 5 Y
EFGH 6 N
XXXX 7 Y
Expected result
col1 col2 col3 col4
ABCD 1 A NULL
ABCD 2 B A
ABCD 3 C B
EFGH 4 A NULL
EFGH 5 B A
EFGH 6 E B
XXXX 7 F NULL
Col4 should hold the data from previous row grouping by the value in Col1.
Please let me know how can this be achieved.
Use lag() function
select *, lag(col3) over (partition by col1 order by col2) as col4
from table t;
However You can also use subquery if your SQL doesn't have LAG()
select *,
(select top 1 col3
from table
where col1 = t.col1 and col2 < t.col2
order by col2 desc
) as col4
from table t;
Assuming SQL Server 2012 or newer...
SELECT
*,
LAG(col3) OVER (PARTITION BY col1 ORDER BY col2) AS col4
FROM
yourTable
If you're on SQL Server 2008 or older...
SELECT
*,
(
SELECT TOP(1) previous.col3
FROM yourTable AS previous
WHERE previous.col1 = yourTable.col1
AND previous.col2 < yourTable.col2
ORDER BY previous.col2 DESC
)
AS col4
FROM
yourTable
If you are on 2008 or earlier, try this:
select t1.col1, t1.col2, t1.col3, t2.col3 as col4
from table1 t1
left join table1 t2 on t1.col1 = t2.col1 and t1.col2 - 1 = t2.col2
the lag() function is the bee's knees, though. Use that, if you can.
Thank you all for the replies. By using the lag function with partition I got the expected result. I missed to used partition previously and due to that I was getting wrong results.
I have a select query
Select col1,col2,col3
from table;
The table contains following rows
col1 col2 col3
A | B | C
B | A | C
C | B | C
I need to get the distinct result which contains a single combination A,B,C by comparing multiple columns.
Result Should be some thing like
col1 col2 col3
A | B | C
the order can be changed of result rows.
How can I achieve this ?
Please try out this, I am not sure about you proper requirement. But on sample data given above. I have came across this solution,
With CTE as
(
Select MIN(col1) as col1 from MyTable
)
Select * from CTE
cross apply
(
Select MIN(col2) as col2 from MyTable
where col2 <> CTE.col1
)as a
cross apply
(
Select MIN(col3) as col3 from MyTable
where col3 not in (CTE.col1,a.col2)
)as b
DEMO HERE
SELECT *
FROM table
WHERE (col1 = 'A' AND col2 = 'B' AND col3 = 'C')
You can also go with this below query if the number of column and the values are known.
The CASE statement is the closest to IF in SQL
SELECT
CASE
WHEN (col1 = 'A' and col2 = 'B' and col3='C') or (col1 = 'C' and col2 = 'A' and col3='B') or (col1 = 'B' and col2 = 'C' and col3='A' )
THEN 1
ELSE 0
END as RESULT, *
FROM table
From the result you can take the required output by checking the value of RESULT==1(integer)
If you want the result as a boolean value then do the CAST like ,
SELECT
CAST(
CASE
WHEN (col1 = 'A' and col2 = 'B' and col3='C') or (col1 = 'C' and col2 = 'A' and col3='B') or (col1 = 'B' and col2 = 'C' and col3='A' )
THEN 1
ELSE 0
END as RESULT_INT)
as RESUTL, *
FROM table
I'm using this query to find duplicate values in a table:
select col1,
count(col1)
from table1
group by col1
having count (col1) > 1
order by 2 desc;
But also I want to add another column from the same table, like this:
select col1,
col2,
count(col1)
from table1
group by col1
having count (col1) > 1
order by 2 desc;
I get an ORA-00979 error with that second query
How can I add another column in my search?
Your query should be
SELECT * FROM (
select col1,
col2,
count(col1) over (partition by col1) col1_cnt
from table1
)
WHERE col1_cnt > 1
order by 2 desc;
Presumably you want to get col2 for each duplicate of col1 that turns up. You can't really do that in a single query^. Instead, what you need to do is get your list of duplicates, then use that to retrieve any other associated values:
select col1, col2
from table1
where col1 in (select col1
from table1
group by col1
having count (col1) > 1)
order by col2 desc
^ Okay, you can, by using analytic functions, as #rs. demonstrated. For this scenario, I suspect that the nested query will be more efficient, but both should give you the same results.
Based on comments, it seems like you're not clear on why you can't just add the second column. Assume you have sample data that looks like this:
Col1 | Col2
-----+-----
1 | A
1 | B
2 | C
2 | D
3 | E
If you run
select Col1, count(*) as cnt
from table1
group by Col1
having count(*) > 1
then your results will be:
Col1 | Cnt
-----+-----
1 | 2
2 | 2
You can't just add Col2 to this query without adding it to the group by clause because the database will have no way of knowing which value you actually want (i.e. for Col1=1 should the DB return 'A' or 'B'?). If you add Col2 to the group by clause, you get the following:
select Col1, Col2, count(*) as cnt
from table1
group by Col1, Col2
having count(*) > 1
Col1 | Col2 | Cnt
-----+------+----
[no results]
This is because the count is for each combination of Col1 and Col2 (each of which are unique).
Finally, by using either a nested query (as in my answer) or an analytic function (as in #rs.'s answer), you'll get the following result (query changed slightly to return the count):
select t1.col1, t1.col2, cnt
from table1 t1
join (select col1, count(*) as cnt
from table1
group by col1
having count (col1) > 1) t2
on table1.col1 = t2.col1
Col1 | Col2 | Cnt
-----+------+----
1 | A | 2
1 | B | 2
2 | C | 2
2 | D | 2
You should list all selected columns in the group by clause as well.
select col1,
col2,
count(col1)
from table1
group by col1, col2
having count (col1) > 1
order by 2 desc;
Cause of Error
You tried to execute an SQL SELECT statement that included a GROUP BY
function (ie: SQL MIN Function, SQL MAX Function, SQL SUM Function,
SQL COUNT Function) and an expression in the SELECT list that was not
in the SQL GROUP BY clause.
select col1,
col2,
count(col1)
from table1
group by col1,col2
having count (col1) > 1
order by 2 desc;
My table:
Col1 Col2
1 xyz
1 abc
2 abc
3 yyy
4 zzz
4 zzz
I have a table with two columns. I want to query for records where col1 has more than one DISTINCT col2 values. In the example table given above, the query should return records for col1 with value "1".
Expected query result:
Col1 Col2
1 xyz
1 abc
SELECT *
FROM tableName
WHERE Col1 IN
(
SELECT Col1
FROM tableName
GROUP BY Col1
HAVING COUNT(DISTINCT col2) > 1
)
SQLFiddle Demo
select t.col1, t.col2
from (
select col1
from tbl
group by col1
having MIN(col2) <> MAX(col2)
) x
join tbl t on t.col1 = c.col1