I have 4 tables
A, B, C, D
Table A:
ct_no ct_type
1010. 1
1011. 1
1012. 2
1013. 3
Table B:
ct_no. jcode
1010. 4
1012. 3
1012. 4
1013. 7
1013. 6
1013. 4
Table C:
Jcode jname
4. ABC
3. lol
7. xyz
Table D:
filno orno. fildate. ct_no
12017. 1. 1010
12017. 2. 1010
12017. 3. 1012
42017. 1. 1010
Now I want table d record with table c jname where table c jcode is 3
Output should be
filno orno ctno jnames
12017 1 1012 lol,ABC
Try this:
select d.*, c.jname from tabled d
inner join tableb b on d.ct_no=b.ct_no and b.Jcode=3
inner join tablec c on b.Jcode =c.Jcode
You need a couple of joins:
SELECT d.*
FROM d
JOIN b ON d.ct_no = b.ct_no
JOIN c ON b.jcode = c.jcode
WHERE c.jcode = 3
Related
I have 3 tables:
table: a
id name
2 A
3 B
table: b
id a b
3 2 Asd Ter Gsdt
4 2 Gsd Gsdt Gsda
5 2 Asd Gsd
6 3 Uty Kggs
7 3 Tyud Hffddf
table: c
id a b
6 3 d
7 3 a
8 3 g
9 3 h
10 4 j
11 5 y
12 5 s
13 6 d
14 6 h
expected output:
a b c d
A 2019-04-06 3 a
B 2019-04-06 6 b
I am unsure how to proceed from this, how?
This query do the job, but there is always a question about speed and performance.
select a.name,
(select c_date from c
join b on (c.b_id = b.id)
where b.a = a.id order by c_date desc limit 1) last_c_date,
popular.b_id,
(select photos->0 from b where id = popular.b_id) photo
from a
join (
select distinct on (a)
b.id b_id, a from b
join c on (b.id = c.b_id)
group by b.id, a
order by a, count(*) desc, b.id
) popular on (popular.a = a.id)
order by a.name
If there will be 2 equaly popular b objects in a region, query takes this with smaller id.
If it will be no b object with entries in c than subquery for photo can be surrounded with coalesce (but now it should work too with null value).
If I have 3 tables A, B and C I understand how to use left join to join them like this:
SELECT *
FROM A LEFT JOIN
B
ON A.col = B.col LEFT JOIN
C
on B.col = C.col
So A to B then B to C
How would I do this:
SELECT *
FROM A LEFT JOIN
B
ON A.col = B.col LEFT JOIN
C
on A.col = C.col
So A to B and then A to C
Would really appreciate any help
I don't see anything wrong with what you're trying to accomplish.
A simple example is at: http://sqlfiddle.com/#!9/6dbbe2/2
There are three tables (A, B, and C):
Table A
id name
1 Alice
2 Bob
3 Carol
4 Don
5 Edith
Table B
id id_A pet
1 5 Tex
2 4 Socks
3 2 Rex
4 1 Percy
5 1 Quinlan
Table C
id id_A hobby
1 1 acting
2 2 boxing
3 4 dancing
4 5 eating
Tables B and C relate to Table A through the id_A foreign key.
A query like you have:
SELECT * FROM A LEFT JOIN B
ON A.id = B.id_a LEFT JOIN C
ON A.id = C.id_a;
works just fine.
I have 2 tables like below:
Table 1
---------
1
2
3
Table 2
--------
A
B
C
How do i join to get an output like below:
Output
---------
1 A
1 B
1 C
2 A
2 B
2 C
3 A
3 B
3 C
Use Cross join:
SELECT *
FROM Table1
CROSS JOIN Table2
You can change the order by replacing * with table fields.
Read more about Cross Join.
OR you could do this:
SELECT Table1.*,Table2.*
FROM Table2,Table1
Result:
ID NAME
1 A
1 B
1 C
2 A
2 B
2 C
3 A
3 B
3 C
You want to do a CROSS JOIN and that will give you the Cartesian product of all the rows.
See http://en.m.wikipedia.org/wiki/Join_(SQL)
select * from table 1,table 2 .
For o/p like A 1
A 2
A 3
B 1
B 2
B 3
C 1
C 2
C 3
just
I would like to know what's the logic for multiple joins (for example below)
SELECT * FROM B returns 100 rows
SELECT B.* FROM B LEFT JOIN C ON B.ID = C.ID returns 120 rows
As I know using left join will returns any matching data from the left table which is B if data are found for both table. But how come when using left join, it returns more data than table B itself?
What am I do wrong or misunderstood here? Any guidance are very appreciated. Thanks in advance.
Let be table B:
id
----
1
2
3
Let be table C
id name
------------
1 John
2 Mary
2 Anne
3 Stef
Any id from b is matched with ids from c, then id=2 will be matched twice. So a left join on id will return 4 rows even if base table B has 3 rows.
Now look at a more evil example:
Table B
id
----
1
2
2
3
4
table C
id name
------------
1 John
2 Mary
2 Anne
3 Stef
Every id from b is matched with ids from c, then first id=2 will be matched twice and second id=2 will be matched twice so the result of
select b.id, c.name
from b left join c on (b.id = c.id)
will be
id name
------------
1 John
2 Mary
2 Mary
2 Anne
2 Anne
3 Stef
4 (null)
The id=4 is not matched but appears in the result because is a left join.
Look at the following example :
B = {1,2}
C = {(1,a),(1,b),(1,c),(1,d),(1,e)}
The result of B left join C will be :
1 | a
1 | b
1 | c
1 | d
1 | e
2 | null
The number of rows in the result is definitely larger than rows in B (2).
In general the number of rows in result of B left join C is bounded by B.size + C.size and not only by B.size as you think...
As per your query it do the join to B Table with C and B table is Left Table so it will display all the records of Left table in our case it is B and related from other Table in our Case it is C.
id address retailer
1 A 11
2 A 11
3 A 11
4 A 12
5 A 13
6 B 12
7 B 12
8 B 13
My output should be
id address retailer
1 A 11
4 A 12
5 A 13
6 B 12
8 B 13
i.e my query should return id's which have same address but not same retailer.
How toget this?
Try to use group by clause as below:
select min(id), address, retailer
from tab
group by address, retailer
Assuming you're joining on columns with no duplicates, which is by far the most common case:
An inner join of A and B gives the result of A intersect B, i.e. the inner part of a venn diagram intersection.
An outer join of A and B gives the results of A union B, i.e. the outer parts of a venn diagram union.
Examples:
Suppose you have two Tables, with a single column each, and data as follows:
A B
- -
1 3
2 4
3 5
4 6
Note that (1,2) are unique to A, (3,4) are common, and (5,6) are unique to B.
Inner join:
An inner join using either of the equivalent queries gives the intersection of the two tables, i.e. the two rows they have in common.
select *
from a
INNER JOIN b on a.a = b.b;
select a.*,b.*
from a,b
where a.a = b.b;
a | b
--+--
3 | 3
4 | 4
Left outer join:
A left outer join will give all rows in A, plus any common rows in B.
select *
from a
LEFT OUTER JOIN b on a.a = b.b;
select a.*,b.*
from a,b
where a.a = b.b(+);
a | b
--+-----
1 | null
2 | null
3 | 3
4 | 4
Full outer join:
A full outer join will give you the union of A and B, i.e. All the rows in A and all the rows in B. If something in A doesn't have a corresponding datum in B, then the B portion is null, and vice versa.
select *
from a
FULL OUTER JOIN b on a.a = b.b;
a | b
-----+-----
1 | null
2 | null
3 | 3
4 | 4
null | 6
null | 5
select min(id) as id,address, retailer
from table1
group by address, retailer
order by id
The query you need is:
SELECT min(id), address, retailer
FROM table1 AS t1
group by address, retailer
order by address
Here's the source
Use This: It's working:
SELECT * FROM `sampletable` GROUP BY address, retailer