I'm looking for an sql answer on how to merge two tables without anything in common.
So let's say you have these two tables without anything in common:
Guys Girls
id name id name
--- ------ ---- ------
1 abraham 5 sarah
2 isaak 6 rachel
3 jacob 7 rebeka
8 leah
and you want to merge them side-by-side like this:
Couples
id name id name
--- ------ --- ------
1 abraham 5 sarah
2 isaak 6 rachel
3 jacob 7 rebeka
8 leah
How can this be done?
I'm looking for an sql answer on how to merge two tables without anything in common.
You can do this by creating a key, which is the row number, and joining on it.
Most dialects of SQL support the row_number() function. Here is an approach using it:
select gu.id, gu.name, gi.id, gi.name
from (select g.*, row_number() over (order by id) as seqnum
from guys g
) gu full outer join
(select g.*, row_number() over (order by id) as seqnum
from girls g
) gi
on gu.seqnum = gi.seqnum;
Just because I wrote it up anyway, an alternative using CTEs;
WITH guys2 AS ( SELECT id,name,ROW_NUMBER() OVER (ORDER BY id) rn FROM guys),
girls2 AS ( SELECT id,name,ROW_NUMBER() OVER (ORDER BY id) rn FROM girls)
SELECT guys2.id guyid, guys2.name guyname,
girls2.id girlid, girls2.name girlname
FROM guys2 FULL OUTER JOIN girls2 ON guys2.rn = girls2.rn
ORDER BY COALESCE(guys2.rn, girls2.rn);
An SQLfiddle to test with.
Assuming, you want to match guys up with girls in your example, and have some sort of meaningful relationship between the records (no pun intended)...
Typically you'd do this with a separate table to represent the association (relationship) between the two.
This wouldn't give you a physical table, but it would enable you to write an SQL query representing the final results:
SELECT Girls.ID AS GirlId, Girls.Name AS GirlName, Guys.ID AS GuyId, Guys.Name AS GuyName
FROM Couples INNER JOIN
Girls ON Couples.GirlId = Girls.ID INNER JOIN
Guys ON Couples.GuyId = Guys.ID
which you could then use to create a table on the fly using the Select Into syntax
SELECT Girls.ID AS GirlId, Girls.Name AS GirlName, Guys.ID AS GuyId, Guys.Name AS GuyName
INTO MyNewTable
FROM Couples INNER JOIN
Girls ON Couples.GirlId = Girls.ID INNER JOIN
Guys ON Couples.GuyId = Guys.ID
(But standard Normalization rules would say it's best to keep them in distinct tables rather than creating a temp table, unless there's a performance reason not to do so.)
I need this all the time, -- creating templates in Excel using input from my tables. This pulls from one table that has my regions, the other with the quarters in a year. the result gives me one region name for each quarter/period.
SELECT b.quarter_qty, a.mkt_name FROM TBL_MKTS a, TBL_PERIODS b
Related
This question already has answers here:
What's the SQL query to list all rows that have 2 column sub-rows as duplicates?
(10 answers)
Closed last year.
Suppose I have the following schema:
student(name, siblings)
The related table has names and siblings. Note the number of rows of the same name will appear the same number of times as the number of siblings an individual has. For instance, a table could be as follows:
Jack, Lucy
Jack, Tim
Meaning that Jack has Lucy and Tim as his siblings.
I want to identify an SQL query that reports the names of all students who have 2 or more siblings. My attempt is the following:
select name
from student
where count(name) >= 1;
I'm not sure I'm using count correctly in this SQL query. Can someone please help with identifying the correct SQL query for this?
You're almost there:
select name
from student
group by name
having count(*) > 1;
HAVING is a where clause that runs after grouping is done. In it you can use things that a grouping would make available (like counts and aggregations). By grouping on the name and counting (filtering for >1, if you want two or more, not >=1 because that would include 1) you get the names you want..
This will just deliver "Jack" as a single result (in the example data from the question). If you then want all the detail, like who Jack's siblings are, you can join your grouped, filtered list of names back to the table:
select *
from
student
INNER JOIN
(
select name
from student
group by name
having count(*) > 1
) morethanone ON morethanone.name = student.name
You can't avoid doing this "joining back" because the grouping has thrown the detail away in order to create the group. The only way to get the detail back is to take the name list the group gave you and use it to filter the original detail data again
Full disclosure; it's a bit of a lie to say "can't avoid doing this": SQL Server supports something called a window function, which will effectively perform a grouping in the background and join it back to the detail. Such a query would look like:
select student.*, count(*) over(partition by name) n
from student
And for a table like this:
jack, lucy
jack, tim
jane, bill
jane, fred
jane, tom
john, dave
It would produce:
jack, lucy, 2
jack, tim, 2
jane, bill, 3
jane, fred, 3
jane, tom, 3
john, dave, 1
The rows with jack would have 2 on because there are two jack rows. There are 3 janes, there is 1 john. You could then wrap all that in a subquery and filter for n > 1 which would remove john
select *
from
(
select student.*, count(*) over(partition by name) n
from student
) x
where x.n > 1
If SQL Server didn't have window functions, it would look more like:
select *
from
student
INNER JOIN
(
select name, count(*) as n
from student
group by name
) x ON x.name = student.name
The COUNT(*) OVER(PARTITION BY name) is like a mini "group by name and return the count, then auto join back to the main detail using the name as key" i.e. a short form of the latter query
You can do:
select name
from student as s1
where exists (
select s2
from student as s2
where s1.name = s2.name and s1.siblings != s2.siblings
)
I think the best approach is what 'Caius Jard' mentioned. However, additional way if you want to get how many siblings each name has .
SELECT name, COUNT(*) AS Occurrences
FROM student
GROUP BY name
HAVING (COUNT(*) > 1)
I wanted to share another solution I came up with:
select s1.name
from student s1, student s2
where s1.name = s2.name and s1.sibling != s2.sibling;
I am using Oracle SQL to extract the data;
I have supply periods for IDs in 2 systems. I have this working with the below code:
select distinct b.ID_Code, b.supply_start_date, b.supply_end_date, b.system_id
from (
select ID_Code, max(supply_start_date) as max_dt
from tmp_mmt_sup
group by ID_Code) a
inner join tmp_mmt_sup b
on a.ID_Code=b.ID_Code and a.max_dt=b.SUPPLY_START_DATE;
However, I have several records that are on the 2 different systems, but have the same start date/end dates. I only want to keep one of them - not bothered which!
So instead of
ID_Code Start End System
123 01-04-2018 30-04-2018 ABC
123 01-04-2018 30-04-2018 DEF
I only have one of these records.
Many thanks
D
If you don't care which one to return, then one of aggregate functions (such as MIN or MAX) does the job. For example:
select b.id_code,
b.supply_start_date,
b.supply_end_date,
max(b.system_id) system_id --> added MAX here ...
from (select id_code,
max(supply_start_date) as max_dt
from tmp_mmt_sup
group by id_code
) a
inner join tmp_mmt_sup b
on a.id_code = b.id_code and a.max_dt = b.supply_start_date
group by b.id_code, --> ... and GROUP BY here
b.supply_start_date,
b.supply_end_date;
Let's suppose we have a table T1 and a table T2. There is a relation of 1:n between T1 and T2. I would like to select all T1 along with all their T2, every row corresponding to T1 records with T2 values concatenated, using only SQL-standard operations.
Example:
T1 = Person
T2 = Popularity (by year)
for each year a person has a certain popularity
I would like to write a selection using SQL-standard operations, resulting something like this:
Person.Name Popularity.Value
John Smith 1.2,5,4.2
John Doe NULL
Jane Smith 8
where there are 3 records in the popularity table for John Smith, none for John Doe and one for Jane Smith, their values being the values represented above. Is this possible? How?
I'm using Oracle but would like to do this using only standard SQL.
Here's one technique, using recursive Common Table Expressions. Unfortunately, I'm not confident on its performance.
I'm sure that there are ways to improve this code, but it shows that there doesn't seem to be an easy way to do something like this using just the SQL standard.
As far as I can see, there really should be some kind of STRINGJOIN aggregate function that would be used with GROUP BY. That would make things like this much easier...
This query assumes that there is some kind of PersonID that joins the two relations, but the Name would work too.
WITH cte (id, Name, Value, ValueCount) AS (
SELECT id,
Name,
CAST(Value AS VARCHAR(MAX)) AS Value,
1 AS ValueCount
FROM (
SELECT ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Name) AS id,
Name,
Value
FROM Person AS per
INNER JOIN Popularity AS pop
ON per.PersonID = pop.PersonID
) AS e
WHERE id = 1
UNION ALL
SELECT e.id,
e.Name,
cte.Value + ',' + CAST(e.Value AS VARCHAR(MAX)) AS Value,
cte.ValueCount + 1 AS ValueCount
FROM (
SELECT ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Name) AS id,
Name,
Value
FROM Person AS per
INNER JOIN Popularity AS pop
ON per.PersonID = pop.PersonID
) AS e
INNER JOIN cte
ON e.id = cte.id + 1
AND e.Name = cte.Name
)
SELECT p.Name, agg.Value
FROM Person p
LEFT JOIN (
SELECT Name, Value
FROM (
SELECT Name,
Value,
ROW_NUMBER() OVER (PARTITION BY Name ORDER BY ValueCount DESC)AS id
FROM cte
) AS p
WHERE id = 1
) AS agg
ON p.Name = agg.Name
This is an example result:
--------------------------------
| Name | Value |
--------------------------------
| John Smith | 1.2,5,4.2 |
--------------------------------
| John Doe | NULL |
--------------------------------
| Jane Smith | 8 |
--------------------------------
As per in Oracle you can use listagg to achive this -
select t1.Person_Name, listagg(t2.Popularity_Value)
within group(order by t2.Popularity_Value)
from t1, t2
where t1.Person_Name = t2.Person_Name (+)
group by t1.Person_Name
I hope this will solve your problem.
But the comment you have given after #DavidJashi question .. well this is not sql standard and I think he is correct. I am also with David that you can not achieve this in pure sql statement.
I know that I'm SUPER late to the party, but for anyone else that might find this, I don't believe that this is possible using pure SQL92. As I discovered in the last few months fighting with NetSuite to try to figure out what Oracle methods I can and cannot use with their ODBC driver, I discovered that they only "support and guarantee" SQL92 standard.
I discovered this, because I had a need to perform a LISTAGG(). Once I found out I was restricted to SQL92, I did some digging through the historical records, and LISTAGG() and recursive queries (common table expressions) are NOT supported in SQL92, at all.
LISTAGG() was added in Oracle SQL version 11g Release 2 (2009 – 11 years ago: reference https://oracle-base.com/articles/misc/string-aggregation-techniques#listagg) , CTEs were added to Oracle SQL in version 9.2 (2007 – 13 years ago: reference https://www.databasestar.com/sql-cte-with/).
VERY frustrating that it's completely impossible to accomplish this kind of effect in pure SQL92, so I had to solve the problem in my C# code after I pulled a ton of extra unnecessary data. Very frustrating.
Background
I have a table which has six columns. The first three columns create the pk. I'm tasked with removing one of the pk columns.
I selected (using distinct) the data into a temp table (excluding the third column), and tried inserting all of that data back into the original table with the third column being '11' for every row as this is what I was instructed to do. (this column is going to be removed by a DBA after I do this)
However, when I went to insert this data back into the original table I get a pk constraint error. (shocking, I know)
The other three columns are just date columns, so the distinct select didn't create a unique pk for each record. What I'm trying to achieve is just calling a distinct on the first two columns, and then just arbitrarily selecting the three other columns as it doesn't matter which dates I choose (at least not on dev).
What I've tried
I found the following post which seems to achieve what I want:
How do I (or can I) SELECT DISTINCT on multiple columns?
I tried the answers from both Joel,and Erwin.
Attempt 1:
However, with Joels answer the set returned is too large - the inner join isn't doing what I thought it would do. Selecting distinct col1 and col2 there are 400 columns returned, however when I use his solution 600 rows are returned. I checked the data and in fact there were duplicate pk's. Here is my attempt at duplicating Joels answer:
select a.emp_no,
a.eec_planning_unit_cde,
'11' as area, create_dte,
create_by_emp_no, modify_dte,
modify_by_emp_no
from tempdb.guest.temp_part_time_evaluator b
inner join
(
select emp_no, eec_planning_unit_cde
from tempdb.guest.temp_part_time_evaluator
group by emp_no, eec_planning_unit_cde
) a
ON b.emp_no = a.emp_no AND b.eec_planning_unit_cde = a.eec_planning_unit_cde
Now, if I execute just the inner select statement 400 rows are returned. If I select the whole query 600 rows are returned? Isn't inner join supposed to only show the intersection of the two sets?
Attempt 2:
I also tried the answer from Erwin. This one has a syntax error and I'm having trouble googling the spec on the where clause (specifically, the trick he is using with (emp_no, eec_planning_unit_cde))
Here is the attempt:
select emp_no,
eec_planning_unit_cde,
'11' as area, create_dte,
create_by_emp_no,
modify_dte,
modify_by_emp_no
where (emp_no, eec_planning_unit_cde) IN
(
select emp_no, eec_planning_unit_cde
from tempdb.guest.temp_part_time_evaluator
group by emp_no, eec_planning_unit_cde
)
Now, I realize that the post I referenced is for postgresql. Doesn't T-SQL have something similar? Trying to google parenthesis isn't working too well.
Overview of Questions:
Why doesn't inner join return an intersection of two sets? From googling this is what I thought it was supposed to do
Is there another way to achieve the same method that I was trying in attempt 2 in t-sql?
It doesn't matter to me which one of these I use, or if I use another solution... how should I go about this?
A select distinct will be based on all columns so it does not guarantee the first two to be distinct
select pk1, pk2, '11', max(c1), max(c2), max(c3)
from table
group by pk1, pk2
You could TRY this:
SELECT a.emp_no,
a.eec_planning_unit_cde,
b.'11' as area,
b.create_dte,
b.create_by_emp_no,
b.modify_dte,
b.modify_by_emp_no
FROM
(
SELECT emp_no, eec_planning_unit_cde
FROM tempdb.guest.temp_part_time_evaluator
GROUP BY emp_no, eec_planning_unit_cde
) a
JOIN tempdb.guest.temp_part_time_evaluator b
ON a.emp_no = b.emp_no AND a.eec_planning_unit_cde = b.eec_planning_unit_cde
That would give you a distinct on those fields but if there is differences in the data between columns you might have to try a more brute force approch.
SELECT a.emp_no,
a.eec_planning_unit_cde,
a.'11' as area,
a.create_dte,
a.create_by_emp_no,
a.modify_dte,
a.modify_by_emp_no
FROM
(
SELECT ROW_NUMBER() OVER(ORDER BY emp_no, eec_planning_unit_cde) rownumber,
a.emp_no,
a.eec_planning_unit_cde,
a.'11' as area,
a.create_dte,
a.create_by_emp_no,
a.modify_dte,
a.modify_by_emp_no
FROM tempdb.guest.temp_part_time_evaluator
) a
WHERE rownumber = 1
I'll reply one by one:
Why doesn't inner join return an intersection of two sets? From googling this is what I thought it was supposed to do
Inner join don't do an intersection. Le'ts supose this tables:
T1 T2
n s n s
1 A 2 X
2 B 2 Y
2 C
3 D
If you join both tables by numeric column you don't get the intersection (2 rows). You get:
select *
from t1 inner join t2
on t1.n = t2.n;
| N | S |
---------
| 2 | B |
| 2 | B |
| 2 | C |
| 2 | C |
And, your second query approach:
select *
from t1
where t1.n in (select n from t2);
| N | S |
---------
| 2 | B |
| 2 | C |
Is there another way to achieve the same method that I was trying in attempt 2 in t-sql?
Yes, this subquery:
select *
from t1
where not exists (
select 1
from t2
where t2.n = t1.n
);
It doesn't matter to me which one of these I use, or if I use another solution... how should I go about this?
yes, using #JTC second query.
Sorry if this has been answered before, but all the related questions didn't quite seem to match my purpose.
I have a table that looks like the following:
ID POSS_PHONE CELL_FLAG
=======================
1 111-111-1111 0
2 222-222-2222 0
2 333-333-3333 1
3 444-444-4444 1
I want to select only distinct ID values for an insert, but I don't care which specific ID gets pulled out of the duplicates.
For Example(a valid SELECT would be):
1 111-111-1111 0
2 222-222-2222 0
3 444-444-4444 1
Before I had the CELL_FLAG column, I was just using an aggregate function as so:
SELECT ID, MAX(POSS_PHONE)
FROM TableA
GROUP BY ID
But I can't do:
SELECT ID, MAX(POSS_PHONE), MAX(CELL_FLAG)...
because I would lose integrity within the row, correct?
I've seen some similar examples using CTEs, but once again, nothing that quite fit.
So maybe this is solvable by a CTE or some type of self-join subquery? I'm at a block right now, so I can't see any other solutions.
Just get your aggregation in a subquery and join to it:
SELECT a.ID, sub.Poss_Phone, CELL_FLAG
FROM TableA as a
INNER JOIN (SELECT ID, MAX(POSS_PHONE) as [Poss_Phone]
FROM TableA
GROUP BY ID) Sub
ON Sub.ID = a.ID and SUB.Poss_Phone = A.Poss_Phone
This will keep integrity between your non-aggregated fields but still give you the MAX(Poss_Phone) per ID.