I have two tables:
Transactions:
+---------+--------------+------------+-----------+
| id | address_from | address_to | value |
+---------+--------------+------------+-----------+
| 1 | 1 | 2 | 1000 |
| 2 | 1 | 2 | 500 |
+---------+--------------+------------+-----------+
Addresses:
+---------+--------------+
| id | address |
+---------+--------------+
| 1 | address1 |
| 2 | address2 |
+---------+--------------+
I need to get all transactions with adresses instead id:
SELECT * FROM transactions tr
JOIN addresses ad ON tr.address_from = ad.id OR tr.address_to = ad.id
WHERE tr.address_from = 1 OR tr.address_to = 1
And then i get following result:
+---------+--------------+-----------+
| id | address | value |
+---------+--------------+-----------+
| 1 | address1 | 1000 |
| 1 | address1 | 1000 |
| 2 | address2 | 500 |
| 2 | address2 | 500 |
+---------+--------------+-----------+
But i need something like this:
+---------+--------------+-------------+-----------+
| id | address_from | address_to | value |
+---------+--------------+-------------+-----------+
| 1 | address1 | address2 | 1000 |
| 2 | address1 | address2 | 500 |
+---------+--------------+-------------+-----------+
How can I get that result?
And isn't it so expensive to do join on two columns?
You could try with 2 join on same table to get the expected result
SELECT tr.id,adf.address as address_from,adt.address as address_to,tr.value
FROM transactions tr
JOIN addresses adf ON tr.address_from = adf.id
JOIN addresses adt ON tr.address_to = adt.id
Related
I have 2 tables, tableStock and tableParts:
tableStock
+----+----------+-------------+
| ID | Num_Part | Description |
+----+----------+-------------+
| 1 | sr37 | plate |
+----+----------+-------------+
| 2 | sr56 | punch |
+----+----------+-------------+
| 3 | sl30 | crimper |
+----+----------+-------------+
| 4 | mp11 | holder |
+----+----------+-------------+
tableParts
+----+----------+-------+
| ID | Location | Stock |
+----+----------+-------+
| 1 | A | 2 |
+----+----------+-------+
| 3 | B | 5 |
+----+----------+-------+
| 5 | C | 2 |
+----+----------+-------+
| 7 | A | 1 |
+----+----------+-------+
And I just want to do this:
+----+----------+-------------+----------+-------+
| ID | Num_Part | Description | Location | Stock |
+----+----------+-------------+----------+-------+
| 1 | sr37 | plate | A | 2 |
+----+----------+-------------+----------+-------+
| 2 | sr56 | punch | NULL | NULL |
+----+----------+-------------+----------+-------+
| 3 | sl30 | crimper | B | 5 |
+----+----------+-------------+----------+-------+
| 4 | mp11 | holder | NULL | NULL |
+----+----------+-------------+----------+-------+
List ALL the rows of the first table and if the second table has the info, in this case 'location' and 'stock', add to the column, if not, just null.
I have been using inner and left join but some rows of the first table disappear because the lack of data in the second one:
select tableStock.ID, tableStock.Num_Part, tableStock.Description, tableParts.Location, tableParts.Stock from tableStock inner join tableParts on tableStock.ID = tableParts.ID;
What can I do?
You can use left join. Here is the demo.
select
s.ID,
Num_Part,
Description,
Location,
Stock
from Stock s
left join Parts p
on s.ID = p.ID
order by
s.ID
output:
| id | num_part | description | location | stock |
| --- | -------- | ----------- | -------- | ----- |
| 1 | sr37 | plate | A | 2 |
| 2 | sr56 | punch | NULL | NULL |
| 3 | sl30 | crimper | B | 5 |
| 4 | mp11 | holder | NULL | NULL |
I have 3 tables as shown:
Video
+----+--------+-----------+
| id | name | videoSize |
+----+--------+-----------+
| 1 | video1 | 1MB |
| 2 | video2 | 2MB |
| 3 | video3 | 3MB |
+----+--------+-----------+
Survey
+----+---------+-----------+
| id | name | questions |
+----+---------+-----------+
| 1 | survey1 | 1 |
| 2 | survey2 | 2 |
| 3 | survey3 | 3 |
+----+---------+-----------+
Sequence
+----+---------+-----------+----------+
| id | videoId | surveyId | sequence |
+----+---------+-----------+----------+
| 1 | null | 1 | 1 |
| 2 | 2 | null | 2 |
| 3 | null | 3 | 3 |
+----+---------+-----------+----------+
I would like to query Sequence and join on both of video and survey tables and merge common columns without specifying the column names (in this case name) like this:
Query Result:
+----+---------+-----------+----------+---------+-----------+-----------+
| id | videoId | surveyId | sequence | name | videoSize | questions |
+----+---------+-----------+----------+---------+-----------+-----------+
| 1 | null | 1 | 1 | survey1 | null | 1 |
| 2 | 2 | null | 2 | video2 | 2MB | null |
| 3 | null | 3 | 3 | survey3 | null | 3 |
+----+---------+-----------+----------+---------+-----------+-----------+
Is this possible?
BTW the below sql doesn't work as it doesn't merge on the name field:
SELECT * FROM "Sequence"
LEFT JOIN "Survey" ON "Survey"."id" = "Sequence"."surveyId"
LEFT JOIN "Video" ON "Video"."id" = "Sequence"."videoId"
This query will show what you want:
select
s.*,
coalesce(y.name, v.name) as name, -- picks the right column
v.videoSize,
y.questions
from sequence s
left join survey y on y.id = s.surveyId
left join video v on v.id = s.videoId
However, the SQL standard requires you to name the columns you want. The only exception being * as shown above.
When I delete some rows from a table it looks like the following table after removing:
+-----+--------+----------+
| ID | Name | Address |
+-----+--------+----------+
| 1 | name1 | address1 |
| 2 | name2 | address2 |
| 8 | name8 | address8 |
| 9 | name9 | address9 |
+-----+--------+----------+
The problem is the ID isn't ordered properly.
I need it to be reordered like this:
+----+---------+----------+
| ID | Name | Address |
+----+---------+----------+
| 1 | name1 | address1 |
| 2 | name2 | address2 |
| 3 | name8 | address8 |
| 4 | name9 | address9 |
+-----+--------+----------+
Is there a command to reorder the column like shown?
I'm using sqlite
I think this type of query should do that:
UPDATE yourTable
SET ID = (SELECT COUNT(*) FROM yourTable ti WHERE ti.ID <= yourTable.ID)
I have two tables tags and users
Table Name: tags
| id | name |
| 1 | one |
| 2 | two |
| 3 | three |
| 4 | four |
| 5 | five |
Table Name: users
| id | fname | tags |
| 1 | Ram | {1,5} |
| 2 | Sham | {1,2,3,4} |
| 3 | Bham | {1,3} |
| 4 | Kam | {5,2} |
| 5 | Lam | {4,2} |
Expected output:
| id | fname | tags |
| 1 | Ram | one, five |
| 2 | Sham | one, two, three, four |
| 3 | Bham | one, three |
| 4 | Kam | five, two |
| 5 | Lam | four, two |
Trial-1 : using JOIN
SELECT I.id, I.fname, I.tags, J.name FROM users I
JOIN tags J ON J.id = ANY(I.cached_tag_ids)
LIMIT 1
Result:
| id | fname | tags |
| 1 | Ram | one |
| 1 | Ram | five |
Expected:
| id | fname | tags |
| 1 | Ram | one, five |
Your tags should have a INTEGER[] type.
CREATE TABLE users(
id SERIAL,
fname VARCHAR(50),
tags INTEGER[]
);
Then,
SELECT I.id, I.fname, array_agg(J.name)
FROM users I
LEFT JOIN tags J
ON J.id = ANY(I.tags)
GROUP BY fname,I.id ORDER BY id
should work. See sqlfiddle
This question may help.
I have 3 like with many - many relationship
As:
TABLE 1 : select * from student;
| id | name |
| 1 | sone |
| 2 | stwo |
| 3 | sthree |
| 4 | sfour |
| 6 | ssix |
TABLE 2 : select * from course;
| id | name |
| 100 | CSE |
| 101 | ECE |
| 102 | ITI |
RELATION_SHIP TABLE : select * from student_course
| id | stu_id | cou_id |
| 1 | 1 | 101 |
| 2 | 2 | 102 |
| 3 | 2 | 100 |
| 4 | 3 | 100 |
| 5 | 3 | 101 |
| 6 | 1 | 101 |
| 1 | 6 | 101 |
I need to write a query to select a student with exactly one course 'CSE' and he should not have any other courses.
Thanks in advance
Use query:
SELECT
sc.`stu_id`,
COUNT(sc.`cou_id`) AS cnt
FROM
student_course sc
GROUP BY sc.`stu_id`
HAVING cnt = 1
AND GROUP_CONCAT(cou_id) LIKE
(SELECT
id
FROM
course
WHERE NAME = 'CSE')