I have one complicated question. I'll try to explain it with example:
have one table that have primary key, and I want to join other table there the first's table primary key is foreign key, and I want If in the second table there is duplicate foreign key to select the number of repeatability. For example:
1-st table:
id name
--- -----
1 Greg
2 Alan
3 George
4 John
5 Peter
2-nd table
id aid data
--- ----- -------
1 2 CCCV
2 2 VVVV
3 3 DDDDD
4 3 SSSS
5 4 PPPPP
I want the result of the join to be:
id(1st table) aid name Data Number
----------- ---- ----- ----- -----
1 null Greg null 1
2 1 Alan CCCV 1
2 2 Alan VVVV 2
3 3 George DDDDD 1
3 4 George SSSS 2
4 5 John PPPPP 1
5 null Peter null 1
I searched a lot, I couldn't find anything. Maybe I do not know how search, or there is no such thing as what I want to do.
SELECT Table1.id, Table2.id as aid, Table1.name, Table2.data,
GREATEST(1, (SELECT COUNT(*)
FROM Table2 t2
WHERE t2.aid = Table1.id
AND t2.id <= Table2.id))
AS number
FROM Table1
LEFT JOIN Table2
ON Table2.aid = Table1.id
ORDER BY id, aid;
works in both MySQL and PostgreSQL.
As per my comment, you've tagged this both MySQL and PostgreSQL.
This answer is for PostgreSQL.
SELECT
table1.id,
table2.aid,
table1.name,
table2.data,
ROW_NUMBER() OVER (PARTITION BY table1.id ORDER BY table2.aid) AS number
FROM
table1
LEFT JOIN
table2
ON table1.id = table2.aid
Queries for PostgreSQL 8.3 which has no window functions.
With bigger tables it is regularly much faster to use a JOIN instead of a correlated sub-query.
The first query aggregates values for Table2 before joining to Table1, which should befaster, too:
SELECT t1.id, t2.aid, t1.name, t2.data, COALESCE(t2.ct, 1) AS number
FROM Table1 t1
LEFT JOIN (
SELECT x.aid, x.data, count(y.aid) + 1 AS ct
FROM Table2 x
LEFT JOIN Table2 y ON x.aid = y.aid AND x.id > y.id
GROUP BY x.aid, x.data
) t2 ON t2.aid = t1.id
ORDER BY t1.id, t2.ct;
And ORDER BY should be fixed.
Alternative without sub-query. Might be faster, yet:
SELECT t1.id, t2.aid, t1.name, t2.data, count(*) + count(t3.id) AS number
FROM Table1 t1
LEFT JOIN Table2 t2 ON t2.aid = t1.id
LEFT JOIN Table2 t3 ON t3.aid = t2.aid AND t3.id < t2.id
GROUP BY t1.id, t2.aid, t1.name, t2.data
ORDER BY t1.id, count(t3.id);
Not sure, didn't test with a bigger set. Test performance with EXPLAIN ANALYZE. Could you report back your results?
Related
I have two tables, t1 and t2.
Table t1:
Name address id
---- ------- --
rob 32 cgr 12
mary 31 lmo 42
tom axel St 2
Table t2:
ID Flag expense
-- ---- --------
12 Shop 1200
12 Educ 14000
42 educ 4000
Now I will have to create a table which will have attributes from t1 plus two more attributes that is expense in shop and expense in educ
Table t3
Name address id Shop_ex Educ_ex
---- ------- -- ------- -------
rob 32 cgr 12 1200 14000
mary 31 lmo 42 NULL 4000
tom axel st 2 NULL NULL
How to accomplish this?
I tried doing a left join t2 with switch case but it gives me multiple record as the join is becoming one to many.
select
t1.name, t1.address, t1.id,
case
when t2.flag = "shop" then t2.expense
else null
end as shop_ex
case
when t2.flag = "educ" then t2.expense
else null
end as educ_ex
from
t1
left join
t2 on (t1.id = t2.id)
It seems I will have to convert t2 table first before joining, to have a single record on the basis of flag. But I am not sure how to do that.
Please mind the tables are huge and optimized query will be nice.
Please suggest.
You only need to join the first table to the second one, twice:
SELECT t1.Name, t1.address, t1.id, t2a.expense AS Shop_ex, t2b.expense AS Educ_ex
FROM table1 t1
LEFT JOIN table2 t2a
ON t2a.ID = t1.id AND t2a.Flag = 'Shop'
LEFT JOIN table2 t2b
ON t2b.ID = t1.id AND t2b.Flag = 'Educ'
Demo
Let's say i have:
Table1:
ID Name
1 Ann
2 Mike
3 Stan
4 Kyle
Table2:
Pair ID Person1ID Person2ID
1 1 2
2 3 4
I want to select pairs, but with names instead of IDs, so this would be the output:
1 Ann Mike
2 Stan Kyle
I imagine a simple:
inner join Table1 on Table1.ID=Table2.Person1ID
won't work, because I want both of them, not only one.
I'm pretty new to SQL so i'm sorry if there is a simple answer.
You have to join twice and use alias to diference the tables
SELECT t2.PairID, A.Name, B.Name
FROM Table2 t2
JOIN Table1 A
ON t2.Person1ID = A.ID
JOIN Table1 B
ON t2.Person2ID = B.ID
You can join sub query like below:
Select p.PairID, p.Name, q.Name
from
(Select t2.PairID, t1.Name
from Table1 t1 inner join Table2 t2
on t1.ID = t2.Person1ID) p
inner join
(Select t2.PairID, t1.Name
from Table1 t1 inner join Table2 t2
on t1.ID = t2.Person2ID) q
on p.PairID = q.PairID
See the result here in the demo.
in my database i have 2 tables.
table1
i have ID and NAMES
table2
i have ID, IDASSOCIATION, QUANTITY
so
i have 2 names in table1:
john and tom
and in table2 i have 3 lignes
john, 1
tom, 1
john, 1
nombre one is the quantity
in my result i want get
john = 2
and tom = 1
so i do this:
sql = "SELECT t1.*, t2.IDASSOCIATION, (SELECT SUM(t2.id_qte) FROM associationdepotarticle t2 WHERE t1.fusiontable = t2.fusiontable GROUP BY t2.IDASSOCIATION) as id_qte FROM articletable t1, associationdepotarticle t2";
but i not get this:
john = 2
tom = 1
why ? what i will do, i need correction please
You can just join the tables together and use sum:
select t1.name, sum(t2.quantity)
from table1 t1
join table2 t2 on t1.id = t2.idassociation
group by t1.name
It's not completely clear from your sample data what to join on, but I assume it's the idassociation field. If you want to return those names in table1 which aren't in table2, then use an outer join.
I have three tables: Table1, Table2, Table1Table2Mapping.
Each tabel1 data having multiple data in tabel1, this table1 relation table2 is done through the mapping table the Primary key of the table1 and table2 is put in mapping table.
Table1:
Table1_ID Name ,Other columns
--------- ---- ------
1 Name1
2 Name2
3 Name3
Table2:
Table2_ID Title
--------- -----
101 Title1
102 Title2
103 Title3
104 Title4
105 Title5
Table1Table2Mapping:
Table1_ID Table2_ID
--------- ------------
1 101
1 102
2 103
3 104
3 105
I am getting all the related rows from table1 and its relation in table1 through mappping table
I need to select single row for each Table1 row.
Like this
Table1_ID Name Title
--------- ------- -----
1 Name1 Title1
2 Name2 Title3
3 Name3 Title4
The CROSS APPLY will do the trick:
SELECT
T1.Table1_ID
, T1.Name
, TMP.Title
FROM
Table1 T1
CROSS APPLY (
SELECT TOP(1)
T2.Title
FROM
Table2 T2
INNER JOIN Table1Table2Mapping TTM
ON T2.Table2_ID = TTM.Table2_ID
WHERE
TTM.Table1_ID = T1.Table1_ID
ORDER BY
TTM.TAble2_ID ASC -- You can change this order to what you want
) TMP
You can change the order of the subquery.
SQL Fiddle
Using CROSS APPLY in TechNet
EDIT
IF it is enough, you can use aggregation too:
SELECT
T1.Table1_ID
, T1.Name
, MIN(T2.Title) -- You can use MAX
FROM
Table1 T1
INNER JOIN Table1Table2Mapping TTM
ON TTM.Table1_ID = T1.Table1_ID
INNER JOIN Table2 T2
ON T2.Table2_ID = TTM.Table2_ID
GROUP BY
T1.Table1_ID
, T1.Name
(This gives the same result for the provided dataset, but in real life, the result of this and the previous solution mostly different!
use outer apply in sql server 2005 and later
Select Table1.*, ttt.Title From Table1 Outer Apply
(Select Top 1 Table2.* From Table2 Inner Join Table1Table2Mapping
On Table2.Table2_Id = Table1Table2Mapping.Table2_Id
Where Table1.Table1_Id = Table1Table2Mapping.Table1_Id) ttt
I am attempting to do something using MSSQL that I believe is possible (easily) but I do not know how to vocalize the correct search string. I have the situation below.
Table A
UID | Value....
1 | a
2 | b
3 | c
Table B
PartTypes_uid_fk | Value....
1 | a
1 | b
1 | c
1 | d
1 | e
3 | 67
3 | 1354
I am attempting to get the following result, query Table A for all results {TableA.*} and on the same row result show the number of table b references {count TableB.tableA_fk}
What I have so far is the following.
SELECT DISTINCT t1.uid, CONVERT(varchar(MAX), t1.Name) AS Name, CONVERT(varchar(MAX), t1.Description) AS Description,
Count(t2.Items_uid_fk) OVER (Partition By t2.PartTypes_uid_fk) as Count
FROM [Table1] as t1 left outer join Table2 as t2 on t2.PartTypes_uid_fk=t1.uid;
This works for all of Table A records with an associated record in Table B but if there are 0 entries in Table B it won't work. The conversion of the varchars was required due to the fact they are ntext format and it was distinct.
Thank you for all your help in advance.
Stephen
Instead of running into problems with the GROUP BY on N/TEXT columns, and to run faster, you would want to pre-aggregate the B table and LEFT JOIN that against A.
select t1.*, ISNULL(t2.c, 0) AS CountOfB
from table1 t1
left join
(
select parttypes_uid_fk, count(*) c
from table2
group by parttypes_uid_fk
) t2 on t2.PartTypes_uid_fk=t1.uid
It's easier than that:
SELECT t1.uid, t1.Name, COUNT(*)
FROM [Table1] t1
LEFT JOIN [Table2] t2 ON t2.PartTypes_uid_fk = t1.uid
GROUP BY t1.uid, t1.Name
Your query should be
SELECT t1.uid,
CONVERT(varchar(MAX), t1.Name) AS Name,
CONVERT(varchar(MAX), t1.Description) AS Description,
Count(t2.Items_uid_fk) CountItems
FROM [Table1] as t1 left outer join Table2 as t2 on t1.uid = t2.PartTypes_uid_fk
GROUP BY uid, t1.name, t1.Description;