maybe someone can help me.
I have 2 sql tables:
// groups
| id_group | namegroup |
+------------+-----------+
| 30 | s |
// contacts
| name | group |
+------+-------+
| juan | s |
I need to DELETE a group from ID, but no has contacts associated with it.
I test the following query but doesnt work.
DELETE
FROM group
WHERE id_group = 30
AND (
SELECT
count(*) AS id
FROM contacts co
INNER JOIN GROUP c ON co. GROUP = c.namegroup
WHERE c.id_group = 30
) = 0
Thanks
You can try the following query if you want to delete group having ID = 30 only if the group is not associated to any contact :
Query #1:
DELETE
`groups`
FROM `groups`
LEFT JOIN contacts
ON contacts.`group` = `groups`.namegroup
WHERE `groups`.id_group = 30
AND contacts.`group` IS NULL;
And if you want to delete all groups which don't have any associated contact then try the following query instead:
Query #2:
DELETE
`groups`
FROM `groups`
LEFT JOIN contacts
ON contacts.`group` = `groups`.namegroup
WHERE contacts.`group` IS NULL;
If you define firigen key mysql will handle this issue and you do not need to do anything
In these cases(without forigen key) i usually first run following query:
select count(*) as id from contacts co inner join group c on co.group=c.namegroup where c.id_group=30
And say to user which if they can delete or not and if he could delete that row:
delete from group where id_group=30
I tried to find a solution like query which you had but could not and suggest this solution for you.
Related
I am working on a photography project and I am facing a bit issue with joining tables and retrieving data from mysql database.
I have created two tables for this project. One table named cm_team is for team members and another table named cm_events for photography events..Assume to shoot a event, we require 6 persons and the id of the person is stored in cm_events table.
As you can see from the above images.. I am storing the id's of members of cm_team in cm_events table.. I wish to obtain the name of the team member in the respective highlighted fields in the cm_events table..Any help is highly appreciated.
for example my desired output should be: instead of 5 under team_lead heading, I should get the name corresponding to 5 i.e Arjun
Something like this? (cleaner and faster than subqueries)
SELECT
`event`.client_name,
`event`.client_number,
# some more event cols ..
`team_lead`.`cm_name` AS `team_lead`,
`candid_photo`.`cm_name` AS `candid_photo`,
`candid_video`.`cm_name` AS `candid_video`,
`traditional_photo`.`cm_name` AS `traditional_photo`,
`traditional_video`.`cm_name` AS `traditional_video`,
`helper`.`cm_name` AS `helper`
FROM cm_events `event`
JOIN cm_team `team_lead` ON `team_lead`.`cm_code` = `event`.`team_lead`
JOIN cm_team `candid_photo` ON `candid_photo`.`cm_code` = `event`.`candid_photo`
JOIN cm_team `candid_video` ON `candid_video`.`cm_code` = `event`.`candid_video`
JOIN cm_team `traditional_photo` ON `traditional_photo`.`cm_code` = `event`.`traditional_photo`
JOIN cm_team `traditional_video` ON `traditional_video`.`cm_code` = `event`.`traditional_video`
JOIN cm_team `helper` ON `helper`.`cm_code` = `event`.`helper`
With Sub queries
DROP TABLE IF EXISTS T,t1;
CREATE TABLE T (
id int, name varchar(10));
insert into t values
(1 , 'aaa'),
(2 , 'bbb');
create table t1 (
id int, team_lead int,team_a int);
insert into t1 values
(1,1,2),
(2,2,2);
select t1.id, (select t.name from t where t.id = t1.team_lead) team_lead,
(select t.name from t where t.id = t1.team_a) team_a
from t1;
+------+-----------+--------+
| id | team_lead | team_a |
+------+-----------+--------+
| 1 | aaa | bbb |
| 2 | bbb | bbb |
+------+-----------+--------+
2 rows in set (0.001 sec)
The question has been resolved. But if you have a "better" or another way to do it then feel free to add a comment! Thanks all for reading! :)
I'm trying to make a dynamic query. Everything is working perfectly except for one thing. I've Google'd for days but I can't figure out how I can make the following work;
SELECT project.name, project.description, track.name, track.description
, SDG.position, SDG.title, SDG.description
, sprint_numbers.number, sprint_options.option
, resources.name, resources.description
, URLs.URL
FROM project INNER JOIN track ON project.track_id = track.id
INNER JOIN project_SDG ON project.id = project_SDG.project_id
INNER JOIN SDG ON project_SDG.SDG_id = SDG.id
INNER JOIN sprint ON sprint.project_id = project.id
INNER JOIN sprint_numbers ON sprint_numbers.id = sprint.sprint_number_id
INNER JOIN sprint_options ON sprint_options.id = sprint.sprint_option_id
INNER JOIN resources ON project.id = resources.project_id
INNER JOIN URLs ON URLs.id = resources.id
WHERE 1=1
AND MATCH (project.name) AGAINST (:name_project)
AND MATCH (project.description) AGAINST (:description_project)
AND SDG.id = :SDG_1
AND SDG.id = :SDG_2
The query executes but does not return anything. The problem is that the SDG.id can't be true to both :SDG_1 and :SDG_2.
Using the OR operator works, but that does not return it the way I want. It must "act" as an AND operator. (:SDG_1 & :SDG_2 are the names of the PHP variables that bind to the SQL statement parameters.)
The query should filter for both values. The values given to :SDG_1 and :SDG_2 must both exist in the SDG.id column of the project_SDG table. If the value of :SDG_1 exists, but :SDG_2 not, then the query should not return anything.
I found this on StackOverflow but it did not work for me: SELECTING with multiple WHERE conditions on same column
I hope someone can help me out.
EDIT: minimal reproducible example
QUERY:
SELECT * FROM project
INNER JOIN project_SDG ON project.id = project_SDG.project_id
INNER JOIN SDG ON project_SDG.SDG_id = SDG.id
WHERE SDG.id = 1 AND SDG.id = 7 AND SDG.id = 14 AND SDG.id = 17
Project table
+------------------+---------------------------+------------+
| id name | description | track_id |
+------------------+---------------------------+------------+
| 1 project name | This is a description 2 | |
+------------------+---------------------------+------------+
SDG table
+-----+-----------+-------------+---------------------------------------------+
| id | position | title | description |
+-----+-----------+-------------+---------------------------------------------+
| 1 | 1 | SDG 1 to 17 | There're multiple SDGs ranging from 1 to 17 |
| 17 | 17 | SDG 1 to 17 | There're multiple SDGs ranging from 1 to 17 |
+-----+-----------+-------------+---------------------------------------------+
project.SDG (bridge-table)
+------------+--------+
| project.id | SDG.id |
+------------+--------+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
+------------+--------+
You want for each project.id both values :SDG_1 and :SDG_2 to exist for SDG.id, so use this in the WHERE clause:
WHERE 1=1
AND MATCH (project.name) AGAINST (:name_project)
AND MATCH (project.description) AGAINST (:description_project)
AND project.id IN (
SELECT project_id
FROM project_SDG
WHERE SDG_id IN (:SDG_1, :SDG_2)
GROUP BY project_id
HAVING COUNT(DISTINCT SDG_id) = 2
)
Could you provide a minimal reproducible example for your query?
Generally speaking, one field cannot be equal to two different values in the same time. So, you have either mixed up the logical operators or you need two different fields.
I can assume that in your case there may be several related records with different values. In this case, you need to join the same table twice with different aliases. Let's say as SDG1 and SDG2. After that you can compare
... `SDG1`.id = :SDG_1 AND `SDG2`.id = :SDG_2
Update:
The win trick is groupping. You can enumerate all required SDG IDs and count how many of them is in group. Just for example in case of two IDs:
SELECT project.id
FROM project
JOIN project_SDG ON project_SDG.project_id = project.id
JOIN SDG ON SDG.id = project_SDG.SDG_id
WHERE SDG.id IN(1,2)
GROUP BY project.id
HAVING COUNT(*) = 2
See my sandbox here: https://www.db-fiddle.com/f/pixe3Zcs75Mq2PyCYPk913/0
If you need all project's fields, you have to put this into sub-query as
... WHERE id IN ( subquery here )
Subquery example: https://www.db-fiddle.com/f/pixe3Zcs75Mq2PyCYPk913/1
I have already answered here, but I have another approch.
1. Find bunch of IDs assotiated with some project
To find project IDs we can test lonely pivot table without any join:
SELECT project_id FROM project_SDG
WHERE SDG_id IN(1,2,6)
GROUP BY project_id HAVING COUNT(*) = 3
it gives us list of Project IDs
2. Access all project fields and add extra conditions
SELECT project.*
FROM project
JOIN (
SELECT project_id FROM project_SDG
WHERE SDG_id IN(1,2,6)
GROUP BY project_id HAVING COUNT(*) = 3
) AS ids ON ids.project_id = project.id
WHERE
MATCH(project.name) AGAINST ('project') AND
MATCH(project.description) AGAINST ('sit')
you can play with it here: https://www.db-fiddle.com/f/pixe3Zcs75Mq2PyCYPk913/3
3. Prepare query on the PHP side
I will use known technique to prepare SQL statement.
$ids = [1, 2, 6]; // it can come from request parameters
$text1 = 'project';
$text2 = 'sit';
// build ?,?,?,... pattern
$qmarks = implode(',', array_fill(0, count($ids), '?'));
// Use SQL query above
$sth = $dbh->prepare("
SELECT project.*
FROM project
JOIN (
SELECT project_id FROM project_SDG
WHERE SDG_id IN({$qmarks})
GROUP BY project_id HAVING COUNT(*) = ?
) AS ids ON ids.project_id = project.id
WHERE
MATCH(project.name) AGAINST (?) AND
MATCH(project.description) AGAINST (?)
");
$sth->execute(array_merge($ids, [count($ids), $text1, $text2]));
$records = $sth->fetchAll();
I have two tables with the name of customers and installments.i.e.
Customer Table:
id | name |contact |address
1 | xyz |33333333|abc
2 | xrz |33322333|abcd
Installments Table:
id | customer_id |amount_paid |amount_left | date
1 | 1 |2000 |3000 | 13/05/2017
2 | 1 |2000 |1000 | 13/06/2017
Now, I want to fetch the latest installment row from installments table for every user, I can use that with the following query,
SELECT * FROM installments WHERE customer_id=1 ORDER BY `id` DESC LIMIT 1
Now, the issue is that I want to do it for all the customer ids. I tried sub query thing but that doesn't supports multiple rows. I tried to store all customer IDs in an array in PHP and used "IN" but because the number of customers is more than 3000, it takes too long and returns an error of execution time exceeded.
Any kind of help or tip will be really appreciated. Thanks
SELECT
Customers.CustomerId,
Customers.Name,
Customers.Contact,
Customers.Address,
Installments.InstallmentId,
Installments.AmountPaid,
Installments.AmountLeft,
Installments.Date
FROM
Customers
INNER JOIN
(
SELECT
MAX( InstallmentId ) AS MaxInstallmentId,
CustomerId
FROM
Installments
GROUP BY
CustomerId
) AS LatestInstallments ON Customers.CustomerId = LatestInstallments.CustomerId
INNER JOIN Installments ON LatestInstallments.MaxInstallmentId = Installments.InstallmentId
you can do something like this
SELECT c.*,I.* FROM Customer_Table c LEFT JOIN Installments_Table I ON c.id=I.customer_id ORDER BY c.id DESC LIMIT 1
If You wants to add limit of list then only set limit else leave limit part. Untill I got Your Question this will be help you. else your problem can be something else.
SELECT cust.*,inst_disp.* FROM Customer AS cust
LEFT JOIN (
SELECT MAX(id) AS in_id, customer_id
FROM installments
GROUP BY customer_id
) inst
ON inst.customer_id = cust.id
LEFT JOIN installments as inst_disp ON inst_disp.id = inst.in_id
I just want to know one SQL query.
I've got two tables:
id | id_town
1 | 26
id | town
26 | Prague
What's the query if I need to print "Prague"?
Thank you.
PhpMyAdmin prints #1052 - Column 'id' in on clause is ambiguous
I tried this
SELECT town FROM localities JOIN towns ON id = id_town
TRY THIS:
select b.town
from table1 a
inner join table2 b on a.id_town = b.id
I want to select from a table and then make select for each of them.
tables:
category
+====+=======+
| id | title |
+====+=======+
this table has list of category
email
+====+=======+==========+=============+
| id | eMail | domainId | elseColumns |
+====+=======+==========+=============+
this table has list of emails but domains are in another table
domain
+====+========+=============+
| id | domain | elseColumns |
+====+========+=============+
list of domains which used in email
subscriber_category
+========+============+
| userId | categoryId |
+========+============+
list of emails in categories
now the question is how can i list categories and count of emails in them with minimum runtime? my try is waiting 20sec for 200000 email and 20 category.
sql:
SELECT category.*,
(SELECT COUNT(DISTINCT subscriber_category.userId) FROM subscriber_category
JOIN email ON email.id=subscriber_category.userId
JOIN domain ON domain.id=email.domainId
WHERE subscriber_category.categoryId=category.id
AND email.blackList=0
AND domain.blackList=0
) AS qty
FROM category WHERE category.userId=1 ORDER BY category.title ASC
This is your query:
SELECT c.*,
(SELECT COUNT(DISTINCT sc.userId)
FROM subscriber_category sc JOIN
email e
ON e.id = sc.userId JOIN
domain d
ON d.id = e.domainId
WHERE sc.categoryId = c.id AND e.blackList = 0 AND d.blackList = 0
) AS qty
FROM category c
WHERE c.userId = 1
ORDER BY c.title ASC;
The structure is quite reasonable and indexes should help performance. The first index is on category(userId, title, id). This index should be used for the WHERE clause, the ORDER BY, and the correlated subquery.
Next, I assume that you have indexes on the id columns in email and domain. You could make these slightly more applicable to the query if you include the blacklist flag as a second column in the index. More importantly, you want an index on subscriber_category(categoryId, userId). I would also recommend removing the count(distinct) if it is not necessary.