I have the two following tables
table A
| id | name |
| 1 | bob |
| 2 | jill |
| 3 | jojo |
Table A is displayed by using checkboxes.
On the first go, the user checks all three checkboxes so you get the result in table B.
table B
| table_a_id | table_c_id |
| 1 | 2 |
| 2 | 2 |
| 3 | 2 |
But the next time the user goes to edit, they UNCHECK '2' so that it's only:
1
3
How do I write my query (using either mySQL or php) so that TABLE B is updated to:
| table_a_id | table_c_id |
| 1 | 2 |
| 3 | 2 |
DELETE A,B
FROM A
LEFT JOIN B
ON B.table_a_id = A.id
WHERE A.id NOT IN (1,3)
Or use InnoDB with a Foreign key ON DELETE CASCADE, much simpler :)
DELETE
FROM TableB
WHERE (NOT table_a_id IN (1, 3))
AND (table_c_id = 2)
Related
Ok, I have a single MySQL table with the name 'car' and 3 columns.
+----+--------+------------+
| ID | car_id | engine |
+----+--------+------------+
| 1 | 123 | on |
| 2 | 123 | on |
| 3 | 123 | off |
| 4 | 123 | on |
| 5 | 123 | on |
| 6 | 123 | on |
| 7 | 123 | off |
| 8 | 123 | on |
| 9 | 123 | off |
+----+--------+------------+
Now I want to show the trips this car did. The trips would be determined based on car engine start and stop. For example from the above example we can see that user has made 3 trips as total(From on to off). Now What I want is that if there is a query which gives me only 3 results from on to off meaning if somehow the query groups the records by considering a starting point on and ending point off. Is it possible in mysql? or the other way around is doing it manually by fetching all the records and working in arrays?
At the moment I am fetching all the records and doing it manually by looping all the data and doing accordingly But this process is slow.
Can you try it ?
SELECT * from cars WHERE `engine` = 'off' AND id IN(SELECT id+1 FROM `cars` WHERE `engine` = 'on')
I need some help with MySQL/PHP. Which is the faster execution in code point of view.
I have below tables
1. table_content
--------------------------------
id | section | content_id
--------------------------------
1 | A | 15
2 | B | 25
3 | A | 9
--------------------------------
2. table_a
--------------------------------
id | name | message
--------------------------------
9 | John | Hello Everyone
15 | Smita | Hi
17 | Vinayak | How are you?
--------------------------------
3. table_b
--------------------------------
id | label | description
--------------------------------
1 | David | D1
5 | Alia | D2
25 | Vinay | D3
--------------------------------
I have above table structure. For me table_content is main table. I want below output through MySQL/PHP [As array and section as key].
Output
------------------------------------------------
id | section | name | message
------------------------------------------------
1 | A | Smita | Hi
2 | B | Vinay | D3
3 | A | John | Hello Everyone
------------------------------------------------
I have tried with SWITCH case. But not getting exact output.
Which is the better performance and fast execution? with MySQL or PHP. I have thousands of data like this.
Please help me to solve this problem.
Should be acheved via a JOIN.
Also ensure you have configured appropriater indexing, otherwise it will perform badly when you get to a large volume of data.
As i posted in my comment you need to Join the both tables, which must be UNION
SELECT tc.`id`, tc. `section` ,t1.`message`
FROM table_content tc JOIN (SELECT `id`, `name`, `message` FROM table_a UNION SELECT `id`, `label`, `description` FROM table_b) t1
ON tc.`content_id` = t1.`id`
id | section | message
-: | :------ | :-------------
1 | A | Hi
2 | B | D3
3 | A | Hello Everyone
db<>fiddle here
I have a small database:
+-----------+-----------+------------------------+
| Name | Number | Hobby |
+-----------+-----------+------------------------+
| Alex | 2, 3 | Game, Shopping |
+-----------+------------------------------------+
It's mean Number 2 is Game and Number 3 is Shopping.
How can I show above data like this table
+-----------+-----------+
| 2 | Game |
+-----------+-----------+
| 3 | Shopping |
+-----------+------------
Your database is not normalized. You need a third table that will be what's usually called a join table.
The people table. The primary key is id
+-----------+-----------+
| Id | Name |
+-----------+-----------+
| 1 | Alex |
| 2 | Thor |
| 3 | Iron Man |
| 4 | Dr Stange |
| 5 | Thanos |
+-----------+------------
The hobbies Table
+-----------+-----------+
| Id | Name |
+-----------+-----------+
| 1 | Game |
| 2 | Shopping |
| 3 | Fighting |
+-----------+-----------+
Join table called (for example) people_hobbies
+-----------+-----------+
| person_id | hobby_id |
+-----------+-----------+
| 1 | 1 |
| 1 | 2 |
+-----------+-----------+
This people_hobbies table will use person_id and hobby_id to create a multi field primary key. This will ensure that you will not be able to add the same combination twice... which should not even make sense.
person_id is a foreign key that references the id from the people table.
hobby_id is a foreign key that references the id from the hobbies table.
Having foreign keys will let you avoid having a key in the people_hobbies table that do not exist in both the people and the hobbies table.
The example in the table below shows that the person id 1 has two hobbies (1 and 2). For a human, that translates to Alex's hobbies are Game and Shopping.
The above structure will let you manage your DB the way most people do.
Just keep a few things in mind:
You cannot add anything in people_hobbies before they exist in both people and hobbies tables
You must have the CASCADE UPDATE and CASCADE DELETE to the foreign key definitions so that when you delete a person or a hobby from your tables, it will remove the relationship from the people_hobbies table.
SELECT * FROM ints;
+---+
| i |
+---+
| 0 |
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
+---+
SELECT * FROM bad_schema;
+------+--------+----------------+
| name | number | hobby |
+------+--------+----------------+
| Alex | 2, 3 | Game, Shopping |
+------+--------+----------------+
CREATE TABLE better_schema AS
SELECT DISTINCT name
, SUBSTRING_INDEX(SUBSTRING_INDEX(number,',',i+1),',',-1) + 0 number
, TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(hobby,',',i+1),',',-1)) hobby
FROM bad_schema
, ints;
SELECT * FROM better_schema;
+------+--------+----------+
| name | number | hobby |
+------+--------+----------+
| Alex | 2 | Game |
| Alex | 3 | Shopping |
+------+--------+----------+
My question is: Can I do this?
I try many things, some of them are:
Search 1
Search 2
Search 3
Search 4
I need all the info form Table A, and sometimes I need to join this table with Table B. My problem is that when I join both tables, if an specific parameter in Table A is not in Table B just give me the records when the specific parameter are, but I want all the records.
Table A
|--------------------------------|
| Table A |
|-------------------|------------|
| id_table_A | name | id_table_B |
|------------|------|------------|
| 1 | Joe | 1 |
|------------|------|------------|
| 2 | Ben | |
|------------|------|------------|
| 3 | Lya | |
|------------|------|------------|
| 4 | luis | 2 |
|------------|------|------------|
Table B
|----------------------|
| Table B |
|----------------------|
| id_table_B | Elements|
|------------|---------|
| 1 | Car |
|------------|---------|
| 2 | Byke |
|------------|---------|
| 3 | Moto |
|------------|---------|
What I want to show in my View is this:
|------------|------|------------|
| id_table_A | name | Elements |
|------------|------|------------|
| 1 | Joe | Car |
|------------|------|------------|
| 2 | Ben | |
|------------|------|------------|
| 3 | Lya | |
|------------|------|------------|
| 4 | luis | Byke |
|------------|------|------------|
My model
In my model this is what I tried:
"SELECT * FROM table_A, table_B where table_A.id_table_B = table_B.id_table_B"
But this query only show me data 1 and 4.
This can be done or not?
Thanks in advance.
You can use left join
SELECT *
FROM table_A
left join table_B on table_A.id_table_B = table_B.id_table_B
Left join is used when the keys between tables may not always match. In this case, the left join retrieves the correct match where it's possible and the values become NULL when not possible.
SQL LEFT JOIN Documentation
You need an explicit LEFT JOIN as opposed to the implicit INNER JOIN that is used when you simply list the tables like that. https://www.w3schools.com/sql/sql_join_left.asp
i'm new to MySQL and PHP. And i have some problems trying to get data values from two tables in one query using JOIN. What i want to do is query "user_builds" and SUM(amount) where the owner_id=1 AND type=1. The problems comes in now where i have to grab the build_type from another table called "builds".
I have tried to solve this as i mentioned with JOIN, but the closest i came was to get the amount of rows that was equal to how many rows user_id=1 had.
What i want is select the total SUM of "amount"(user_builds) where "type=1"(builds) and "owner_id=1"(user_builds).
I hope you understand what i try to do here, if not i will try to elaborate it more. And also sorry for not providing any of the querys i tried, but as none of them worked it feels irrelevant. Thank you for your time.
Edit:
+-------------------+
| user_builds |
+---------+---------+----------+-------+
| id |owner_id | build_id | amount|
+---------+---------+----------+-------+
| 1 | 1 | 1 | 5 |
| 2 | 2 | 2 | 15 |
| 3 | 2 | 3 | 15 |
| 4 | 1 | 4 | 5 |
| 5 | 1 | 5 | 5 |
| 6 | 1 | 6 | 10 |
+---------+---------+----------+-------+
+----------------------+
| build |
+---------+------------+-----------+--------+
| id | name |description| type |
+---------+------------+-----------+--------+
| 1 | House | desc | 1 |
| 2 | Kitchen | desc | 2 |
+---------+------------+-----------+--------+
I want to query "user_builds" and get the total of "amount" where owner_id=1 and type=1. (type is found in "build" table).
Try this code, I hope it works appropriately.
select sum(ub.amount)
from user_builds ub
left join build b
on ub.build_id = b.id
where b.type=1
and ub.owner_id = 1
select SUM(amount) from user_builds left join builds on build.type = user_builds.type where "owner_id=1"
try this query and replace my query field with your original fields
best of luck...