Suppose I have a table with many columns, but only two of them are important to me. I want to check for the 1 to 1 relationship between col1 and col2(and if col1 exists more then one record of col2 it must be shown). Here is my sql query:
select tbl1.col1, count(tbl1.col1)
from admin.table_1 tbl1
left join ( select col2,col1 from admin.table_1) tbl2
on tbl1.col1 = tbl2.col1 and tbl1.col2 = tbl2.col2
group by tbl1.col1
having count(tbl1.col1) >1;
Is my calculation correct? Maybe it can be improved?
You need to check there is one col2 for each col1 and the reflexive relationship that there is one col1 for each col2. You can perform these checks using an analytic COUNT function:
Oracle Setup:
CREATE TABLE TABLE_1 ( col1, col2 ) AS
SELECT 1, 1 FROM DUAL UNION ALL
SELECT 2, 2 FROM DUAL UNION ALL
SELECT 2, 3 FROM DUAL UNION ALL
SELECT 4, 4 FROM DUAL UNION ALL
SELECT 5, 4 FROM DUAL;
Query:
SELECT col1, col2
FROM (
SELECT col1,
col2,
COUNT( col1 ) OVER ( PARTITION BY col2 ) AS col1_per_col2,
COUNT( col2 ) OVER ( PARTITION BY col1 ) AS col2_per_col1
FROM table_1
)
WHERE col1_per_col2 > 1
OR col2_per_col1 > 1;
Output:
COL1 | COL2
---: | ---:
2 | 2
2 | 3
4 | 4
5 | 4
db<>fiddle here
You can directly use the group by as following:
SELECT
TBL1.COL1,
COUNT(1)
FROM
ADMIN.TABLE_1 TBL1
GROUP BY
TBL1.COL1
HAVING
COUNT(DISTINCT TBL1.COL2) > 1;
Cheers!!
You can use exists :
select tbl1.col1, count(tbl1.col1)
from admin.table_1 tbl1
where exists ( select 1
from admin.table_1 tbl2
where tbl2.col1 = tbl1.col2 )
group by tbl1.col1
having count(tbl1.col1)>1
Related
Input:
col1 col2
------------
1 A
2 1
3 B
4 2
5 C
6 Null
Output i want
Col1 Col2
__________
A 1
B 2
C Null
Oh, I see. Assuming there are no gaps in col1, you can use aggregation using arithmetic:
select max(case when mod(id, 2) = 0 then col2 end),
max(case when mod(id, 2) = 1 then col2 end)
from t
group by floor((id - 1) / 2);
Another method uses lead():
select col2, next_col2
from (select t.*, lead(col2) over (order by id) as next_col2
from t
) t
where mod(id, 2) = 1;
Use join to the next row of the same table and limit to every other row.
select t1.col2 col1, t2.col2
from tab t1
join tab t2 on t1.col1 = t2.col1 -1
where mod(t1.col1,2) = 1
C C
- -
A 1
B 2
C
Again, it assumes that your sequence in col1is without gaps.
This is an application of PIVOT, available since Oracle 11.1. (A much shorter solution is possible in Oracle 12.1 and higher, using MATCH_RECOGNIZE, but the question is explicitly tagged oracle11g.)
I use the analytic function ROW_NUMBER() to prepare the data, so that we don't need to assume anything about the ordering column - it may have gaps, and/or it doesn't even have to be a number column, it can be date or string or anything else that can be ordered.
Setup:
create table sample_data (col1, col2) as
select 1, 'A' from dual union all
select 2, '1' from dual union all
select 3, 'B' from dual union all
select 4, '2' from dual union all
select 5, 'C' from dual union all
select 6, null from dual
;
Query and output:
select col1, col2
from (
select ceil(row_number() over (order by col1) / 2) as r,
mod (row_number() over (order by col1) , 2) as c, col2
from sample_data
)
pivot (min(col2) for c in (1 as col1, 0 as col2))
order by r
;
COL1 COL2
---- ----
A 1
B 2
C
Just for fun, and for whoever may have this problem in Oracle 12 or higher, here is the match_recognize solution:
select col1, col2
from sample_data
match_recognize(
order by col1
measures x.col2 as col1, y.col2 as col2
pattern ( x y? )
define x as null is null
);
How can I create the following table in Oracle.
+------+------+
| col1 | col2 |
+------+------+
| A | 1 |
| B | 2 |
+------+------+
I need it as an itermediate table in a WITH-clause.
You can use:
with t as (
select 'A' as col1, 1 as col2 union all
select 'B' as col1, 2 as col2
)
You can then use t throughout the rest of the query.
Please use below query,
with tbl as
(
select 'A' as col1, 1 as col2 from dual
UNION
select 'B' as col1, 2 as col2 from dual
)
select * from tbl;
When you create a common table expression such as this you can name the columns in the CTE definition, which saves having them scattered through the SELECT statement:
WITH cteWork (COL1, COL2) AS
(SELECT 'A', 1 FROM DUAL UNION ALL
SELECT 'B', 2 FROM DUAL)
SELECT *
FROM cteWork
db<>fiddle here
I have a table of two columns
Col1 Col2
A 1
A 2
A 3
B 1
B 2
B 3
Output I need is like this
Col1 Col2
A 1
A 1,2
A 1,2,3
B 1
B 1,2
B 1,2,3
Thank you in advance.
Here is a solution which would work for MySQL. It uses a correlated subquery in the select clause to group concatenate together Col2 values. The logic is that we only aggregate values which are less than or equal to the current row, for a given group of records sharing the same Col1 value.
SELECT
Col1,
(SELECT GROUP_CONCAT(t2.Col2 ORDER BY t2.Col2) FROM yourTable t2
WHERE t2.Col2 <= t1.Col2 AND t1.Col1 = t2.Col1) Col2
FROM yourTable t1
ORDER BY
t1.Col1,
t1.Col2;
Demo
Here is the same query in Oracle:
SELECT
Col1,
(SELECT LISTAGG(t2.Col2, ',') WITHIN GROUP (ORDER BY t2.Col2) FROM yourTable t2
WHERE t2.Col2 <= t1.Col2 AND t1.Col1 = t2.Col1) Col2
FROM yourTable t1
ORDER BY
t1.Col1,
t1.Col2;
Demo
Note that the only real change is substituting LISTAGG for GROUP_CONCAT.
with s (Col1, Col2) as (
select 'A', 1 from dual union all
select 'A', 2 from dual union all
select 'A', 3 from dual union all
select 'B', 1 from dual union all
select 'B', 2 from dual union all
select 'B', 3 from dual)
select col1, ltrim(sys_connect_by_path(col2, ','), ',') path
from s
start with col2 = 1
connect by prior col2 = col2 - 1 and prior col1 = col1;
C PATH
- ----------
A 1
A 1,2
A 1,2,3
B 1
B 1,2
B 1,2,3
6 rows selected.
According to some weird requirement, i need to select the record where all the output values in both the columns should be unique.
Input looks like this:
col1 col2
1 x
1 y
2 x
2 y
3 x
3 y
3 z
Expected Output is:
col1 col2
1 x
2 y
3 z
or
col1 col2
1 y
2 x
3 z
I tried applying the distinct on 2 fields but that returns all the records as overall they are distinct on both the fields. What we want to do is that if any value is present in the col1, then it cannot be repeated in the col2.
Please let me know if this is even possible and if yes, how to go about it.
Great problem! Armunin has picked up on the deeper structural issue here, this is a recursive enumerable problem description and can only be resolved with a recursive solution - base relational operators (join/union/etc) are not going to get you there. As Armunin cited, one approach is to bring out the PL/SQL, and though I haven't checked it in detail, I'd assume the PL/SQL code will work just fine. However, Oracle is kind enough to support recursive SQL, through which we can build the solution in just SQL:
-- Note - this SQL will generate every solution - you will need to filter for SOLUTION_NUMBER=1 at the end
with t as (
select 1 col1, 'x' col2 from dual union all
select 1 col1, 'y' col2 from dual union all
select 2 col1, 'x' col2 from dual union all
select 2 col1, 'y' col2 from dual union all
select 3 col1, 'x' col2 from dual union all
select 3 col1, 'y' col2 from dual union all
select 3 col1, 'z' col2 from dual
),
t0 as
(select t.*,
row_number() over (order by col1) id,
dense_rank() over (order by col2) c2_rnk
from t),
-- recursive step...
t1 (c2_rnk,ids, str) as
(-- base row
select c2_rnk, '('||id||')' ids, '('||col1||')' str
from t0
where c2_rnk=1
union all
-- induction
select t0.c2_rnk, ids||'('||t0.id||')' ids, str||','||'('||t0.col1||')'
from t1, t0
where t0.c2_rnk = t1.c2_rnk+1
and instr(t1.str,'('||t0.col1||')') =0
),
t2 as
(select t1.*,
rownum solution_number
from t1
where c2_rnk = (select max(c2_rnk) from t1)
)
select solution_number, col1, col2
from t0, t2
where instr(t2.ids,'('||t0.id||')') <> 0
order by 1,2,3
SOLUTION_NUMBER COL1 COL2
1 1 x
1 2 y
1 3 z
2 1 y
2 2 x
2 3 z
You can use a full outer join to merge two numbered lists together:
SELECT col1, col2
FROM ( SELECT col1, ROW_NUMBER() OVER ( ORDER BY col1 ) col1_num
FROM your_table
GROUP BY col1 )
FULL JOIN
( SELECT col2, ROW_NUMBER() OVER ( ORDER BY col2 ) col2_num
FROM your_table
GROUP BY col2 )
ON col1_num = col2_num
Change ORDER BY if you require a different order and use ORDER BY NULL if you're happy to let Oracle decide.
What would be the result if another row of
col1 value as 1 and col2 value as xx ?
A single row is better in this case:
SELECT DISTINCT TO_CHAR(col1) FROM your_table
UNION ALL
SELECT DISTINCT col2 FROM your_table;
My suggestion is something like this:
begin
EXECUTE IMMEDIATE 'CREATE global TEMPORARY TABLE tmp(col1 NUMBER, col2 VARCHAR2(50))';
end;
/
DECLARE
cur_print sys_refcursor;
col1 NUMBER;
col2 VARCHAR(50);
CURSOR cur_dist
IS
SELECT DISTINCT
col1
FROM
ttable;
filtered sys_refcursor;
BEGIN
FOR rec IN cur_dist
LOOP
INSERT INTO tmp
SELECT
col1,
col2
FROM
ttable t1
WHERE
t1.col1 = rec.col1
AND t1.col2 NOT IN
(
SELECT
tmp.col2
FROM
tmp
)
AND t1.col1 NOT IN
(
SELECT
tmp.col1
FROM
tmp
)
AND ROWNUM = 1;
END LOOP;
FOR rec in (select col1, col2 from tmp) LOOP
DBMS_OUTPUT.PUT_LINE('col1: ' || rec.col1 || '|| col2: ' || rec.col2);
END LOOP;
EXECUTE IMMEDIATE 'DROP TABLE tmp';
END;
/
May still need some refining, I am especially not happy with the ROWNUM = 1 part.
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE tbl ( col1, col2 ) AS
SELECT 1, 'x' FROM DUAL
UNION ALL SELECT 1, 'y' FROM DUAL
UNION ALL SELECT 2, 'x' FROM DUAL
UNION ALL SELECT 2, 'y' FROM DUAL
UNION ALL SELECT 3, 'x' FROM DUAL
UNION ALL SELECT 3, 'y' FROM DUAL
UNION ALL SELECT 4, 'z' FROM DUAL;
Query 1:
WITH c1 AS (
SELECT DISTINCT
col1,
DENSE_RANK() OVER (ORDER BY col1) AS rank
FROM tbl
),
c2 AS (
SELECT DISTINCT
col2,
DENSE_RANK() OVER (ORDER BY col2) AS rank
FROM tbl
)
SELECT c1.col1,
c2.col2
FROM c1
FULL OUTER JOIN c2
ON ( c1.rank = c2.rank)
ORDER BY COALESCE( c1.rank, c2.rank)
Results:
| COL1 | COL2 |
|------|--------|
| 1 | x |
| 2 | y |
| 3 | z |
| 4 | (null) |
And to address the additional requirement:
What we want to do is that if any value is present in the col1, then it cannot be repeated in the col2.
Query 2:
WITH c1 AS (
SELECT DISTINCT
col1,
DENSE_RANK() OVER (ORDER BY col1) AS rank
FROM tbl
),
c2 AS (
SELECT DISTINCT
col2,
DENSE_RANK() OVER (ORDER BY col2) AS rank
FROM tbl
WHERE col2 NOT IN ( SELECT TO_CHAR( col1 ) FROM c1 )
)
SELECT c1.col1,
c2.col2
FROM c1
FULL OUTER JOIN c2
ON ( c1.rank = c2.rank)
ORDER BY COALESCE( c1.rank, c2.rank)
Here is my sample table
Col1 Col2
A 1
B 1
A 1
B 2
C 3
I want to be able to select distinct records where all rows have the same value in Col1 and Col2. So my answer should be
Col1 Col2
A 1
C 3
I tried
SELECT Col1, Col2 FROM Table GROUP BY Col1, Col2
This gives me
Col1 Col2
A 1
B 1
B 2
C 3
which is not the result I am looking for. Any tips would be appreciated.
Try this out:
SELECT col1, MAX(col2) aCol2 FROM t
GROUP BY col1
HAVING COUNT(DISTINCT col2) = 1
Output:
| COL1 | ACOL2 |
|------|-------|
| A | 1 |
| C | 3 |
Fiddle here.
Basically, this makes sure that amount the different values for col2 are unique for a given col1.
Try this:
SELECT * FROM MYTABLE
GROUP BY Col1, Col2
HAVING COUNT(*)>1
For example SQLFiddle here
you can try either of the below -
select col1, col2 from
(
select 'A' Col1 , 1 Col2
from dual
union all
select 'B' , 1
from dual
union all
select 'A' ,1
from dual
union all
select 'B' ,2
from dual
)
group by col1, col2
having count(*) >1;
OR
select col1, col2
from
(
select col1, col2, row_number() over (partition by col1, col2 order by col1, col2) cnt
from
(
select 'A' Col1 , 1 Col2
from dual
union all
select 'B' , 1
from dual
union all
select 'A' ,1
from dual
union all
select 'B' ,2
from dual
)
)
where cnt>1;