I have 2 tables in 1 database.
In the 2 tables there are several rows with the same contents.
table visitor
--------------------------
id | mytoken1 |
--------------------------
1 | token_abcd |
2 | token_efgh |
3 | token_ijkl |
4 | token_mnop |
--------------------------
table favorites
--------------------------
id | mytoken2 |
--------------------------
1 | token_abcd |
2 | token_efgh |
3 | token_ijkl |
4 | token_mnop |
5 | token_aaaa |
6 | token_bbbb |
7 | token_cccc |
8 | token_dddd |
--------------------------
How do I delete the mytoken2 column that is not in the mytoken1 column?
So in the example above I want to delete 4 rows of data, including:
token_aaaa
token_bbbb
token_cccc
token_dddd
I have tried to find a solution until I was dizzy but it has not been resolved, I hope someone will help me here ..
You can do using NOT IN
DELETE FROM favorites
WHERE token2 NOT IN (SELECT token1 FROM visitor)
You can use NOT EXISTS.
DELETE FROM favorites
WHERE NOT EXISTS (SELECT *
FROM visitor
WHERE visitor.mytoken1 = favorites.mytoken2);
JOIN also can be used here:
DELETE favorites.*
FROM favorites
LEFT JOIN visitor ON visitor.mytoken1 = favorites.mytoken2
WHERE visitor.id IS NULL;
Here you can test SQL query
Related
I created a table (t_subject) like this
| id | description | enabled |
|----|-------------|---------|
| 1 | a | 1 |
| 2 | b | 1 |
| 3 | c | 1 |
And another table (t_place) like this
| id | description | enabled |
|----|-------------|---------|
| 1 | d | 1 |
| 2 | e | 1 |
| 3 | f | 1 |
Right now data from t_subject is used for each of t_place records, to show HTML dropdowns, with all the results from t_subject.
So I simply do
SELECT * FROM t_subject WHERE enabled = 1
Now just for one of t_place records, one record from t_subject should be hidden.
I don't want to simply delete it with javascript, since I want to be able to customize all of the dropdowns if anything changes.
So the first thing I though was to add a place_id column to t_subject.
But this means I have to duplicate all of t_subject records, I would have 3 of each, except one that would have 2.
Is there any way to avoid this??
I thought adding an id_exclusion column to t_subject so I could duplicate records only whenever a record is excluded from another id from t_place.
How bad would that be?? This way I would have no duplicates, so far.
Hope all of this makes sense.
While you only need to exclude one course, I would still recommend setting up a full 'place-course' association. You essentially have a many-to-many relationship, despite not explicitly linking your tables.
I would recommend an additional 'bridging' or 'associative entity' table to represent which courses are offered at which places. This new table would have two columns - one foreign key for the ID of t_subject, and one for the ID of t_place.
For example (t_place_course):
| place_id | course_id |
|----------|-----------|
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 3 | 1 |
| 3 | 3 |
As you can see in my example above, place 3 doesn't offer course 2.
From here, you can simply query all of the courses available for a place by querying the place_id:
SELECT * from t_place_course WHERE place_id = 3
The above will return both courses 1 and 3.
You can optionally use a JOIN to get the other information about the course or place, such as the description:
SELECT `t_course`.`description`
FROM `t_course`
INNER JOIN `t_place_course`
ON `t_course`.`id` = `t_place_course`.`course_id`
INNER JOIN `t_place`
ON `t_place`.`id` = `place_id`
I have two tables in a MySQL database like this:
User:
userid |userid | Username | Plan(VARCHAR) | Status |
-----------+------------+--------------+---------------+---------+
1 | 1 | John | 1,2,3 |1 |
2 | 2 | Cynthia | 1,2 |1 |
3 | 3 | Charles | 2,3,4 |1 |
Plan: (planid is primary key)
planid(INT) | Plan_Name | Cost | status |
-------------+----------------+----------+--------------+
1 | Tamil Pack | 100 | ACTIVE |
2 | English Pack | 100 | ACTIVE |
3 | SportsPack | 100 | ACTIVE |
4 | KidsPack | 100 | ACTIVE |
OUTPUT
id |userid | Username | Plan | Planname |
---+-------+----------+------------+-------------------------------------+
1 | 1 | John | 1,2,3 |Tamil Pack,English Pack,SportsPack |
2 | 2 | Cynthia | 1,2 |Tamil Pack,English Pack |
3 | 3 | Charles | 2,3,4 |English Pack,Sportspack, Kidspack |
Since plan id in Plan table is integer and the user can hold many plans, its stored as comma separated as varchar, so when i try with IN condition its not working.
SELECT * FROM plan WHERE find_in_set(plan_id,(select user.planid from user where user.userid=1))
This get me the 3 rows from plan table but i want the desired output as above.
How to do that.? any help Please
A rewrite off your query what should work is as follows..
Query
SELECT
all columns you need
, GROUP_CONCAT(Plan.Plan_Name ORDER BY Plan.planid) AS Planname
FROM
Plan
WHERE
FIND_IN_SET(Plan.plan_id,(
SELECT
User.Plan
FROM
user
WHERE User.userid = 1
)
)
GROUP BY
all columns what are in the select (NOT the GROUP_CONCAT function)
You also can use FIND_IN_SET on the ON clause off a INNER JOIN.
One problem is that the join won't ever use indexes.
Query
SELECT
all columns you need
, GROUP_CONCAT(Plan.Plan_Name ORDER BY Plan.planid) AS Planname
FROM
User
INNER JOIN
Plan
ON
FIND_IN_SET(Plan.id, User.Plan)
WHERE
User.id = 1
GROUP BY
all columns what are in the select (NOT the GROUP_CONCAT function)
Like i said in the comments you should normalize the table structures and add the table User_Plan whats holds the relations between the table User and Plan.
I have 2 tables:
table1
id | title | author | url
1 | the-test | james-brown | www.thetest.com
2 | the-house | clancy-brown | www.thehouse.com
3 | the-desk | leanne-brown | www.thedesk.com
4 | the-head | julie-brown | www.thehead.com
table2
id | title | author | url**
1 | the-mouse | john-blue | www.themouse.com
2 | the-house | clancy-brown | www.thehouse.com
3 | the-cups | carrie-blue | www.thecups.com
4 | the-head | clancy-brown | www.thehead.com
I need results to show only where both title and author match, i.e.
2 | the-house | clancy-brown | www.thehouse.com
I've tried this:
select *
from table1
inner join table2 on (table1.title=table2.title) AND (table1.author=table2.author)
But it just runs forever (there are actually several hundred thousands rows in the real tables).
Just to note, this works fine:
select *
from table1
inner join table2 on (table1.title=table2.title)
I just can't get it to match both tables. Is there a smarter way to do this?
Thanks for all help in advance.
I think your SQL is fine, you just need to index table1 and table2 on author. Add those indices and the JOIN will be fast enough. You also have an issue that you call the column author in your sample data and name in your first query.
I have a transaction table with timestamps
a transaction has one event and one user.
All transactions have an event,
All events have at least one trasaction,
Each transaction has a user that must exist,
A User will not necessarily have a transaction.
The output will be a sort of the evt list
Output line count should equal db.evt record count.
The first column of each table is the Autoinc unique index.
In transaction, these are fks to the other tables.
The problem is that I need the transaction with the latest timestamp for the evt in the transaction table.
I am still relatively new to SQL (Using MySQL) and while I muddle through joins. I have no idea how to get the latest record by evID by timestamp.
I have looked at other questions on the topic but not found one that addresses mine. (Granted there are 14K on Joins alone, so I may have missed one)
Sample Table Data below:
Table structure is hopefully obvious by I will edit it in if requested.
Edit:
I've changed the names of tables and columns for clarity (and to avoid matching keywords)
I tried Stuart's answer below and got an error:
Answer:
SELECT
eventTable.EvtName AS EvtD,
transTable.TranAct AS LastTrans,
userTable.UserName AS UsrNm
FROM
transTables,
INNER JOIN (
SELECT evtID, MAX(TransID) TransID FROM transTable GROUP BY evtID
) last ON last.evtID = transTable.evtID AND last.TransID = transTable.TransID
INNER JOIN eventTable ON eventTable.evtID = transTable.evtID
INNER JOIN userTable ON userTable.usId = transTable.usId
Response:
#1064 - You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version for the right syntax to use near
'INNER JOIN (
SELECT evtID, MAX(TransID) TransID FROM transTable GROUP BY evt'
at line 7
Tables:
db.transTable
| TransID | EvtID | TranAct | timestamp | UserID
----------------------------------------------------------------
| 1 | 1 | add | 2014-05-08 08:10:00.000 | 3
| 2 | 2 | add | 2014-05-08 09:10:00.000 | 2
| 3 | 3 | add | 2014-05-08 10:10:00.000 | 3
| 4 | 2 | validate | 2014-05-08 11:10:00.000 | 5
| 5 | 3 | validate | 2014-05-08 12:10:00.000 | 3
| 6 | 2 | reverse | 2014-05-08 13:10:00.000 | 1
| 7 | 1 | edit | 2014-05-08 14:10:00.000 | 4
| 8 | 4 | add | 2014-05-08 15:10:00.000 | 3
| 9 | 5 | add | 2014-05-08 16:10:00.000 | 2
db.eventTable
| EvtID | EvtName
-----------------
| 1 | Evt1
| 2 | Evt2
| 3 | Evt3
| 4 | Evt4
| 5 | Evt5
db.userTable
| UserID | UserName
--------------------
| 1 | Usr1
| 2 | Usr2
| 3 | Usr3
| 4 | Usr4
| 5 | Usr5
Desired output:
eventTable.EvtName AS EvtD
transTable.TranAct AS LastTrans
userTable.UserName AS UsrNm
| EvtD | LastTrans | UsrNm
--------------------------
| Evt1 | edit | Usr4
| Evt2 | reverse | Usr1
| Evt3 | validate | Usr3
| Evt4 | add | Usr3
| Evt5 | add | Usr2
Much thanks for any assistance.
Something like this shuold work where a derived table is used to eliminate all transactions except the latest per evId.
SELECT
eventTable.EvtName AS EvtD,
transTable.TranAct AS LastTrans,
userTable.UserName AS UsrNm,
FROM
transTable
INNER JOIN (
SELECT evId, MAX(UID) uid FROM transTable GROUP BY evId
) last ON last.evId = transTable.evId AND last.uid = transTable.uid
INNER JOIN eventTable ON eventTable.evId = transTable.evId
INNER JOIN userTable ON userTable.usId = transTable.usId
I have a question about my DB table structure. I want to know if i'm on the right track or if I have missed a good alternative. Here is the case:
To make it easy to read, I haven't pasted the full contents as my question is only about the structure.
2 tables:
1: id (AI), task
2: id, name, task
Table 1 presents dynamic check-boxes which can be altered by an admin panel so the contents would be like this
1 task1
2 task2
5 task5
(3 & 4 are missing cause the administrator deleted those records).
In table number two are the people who should do the tasks from table 1. And the goal is that the tasks wich are not checked will be displayed.
So the contents of table 2 would be:
1 Name1 1,5
2 Name2 1,2
3 Name3 1,2,5
The numbers in table 2 represent the checked boxes from table 1. So with a query i can compare the numbers from table 2 with the id's from table 1 and display the missing ids as "todo".
In my opinion this looks very overdone, and there must be an easier way to create dynamic options which can be compared and stored as a todo.
Suggestions are welcome!
I suggest you to use basic structure for many-to-many relationship:
tasks users user_tasks
+----+-----------+ +----+-------+ +---------+---------+
| id | name | | id | name | | user_id | task_id |
+----+-----------+ +----+-------+ +---------+---------+
| 1 | Buy milk | | 1 | John | | 1 | 2 |
| 2 | Get drunk | | 2 | Tim | | 3 | 2 |
| 3 | Have fun | | 3 | Steve | | 2 | 4 |
| 4 | Go home | +----+-------+ | 3 | 4 |
+----+-----------+ +---------+---------+
And you can fetch unassigned tasks using following query:
SELECT
tasks.*
FROM
tasks
LEFT JOIN
user_tasks
ON (tasks.id = user_tasks.task_id)
WHERE
user_tasks.user_id IS NULL
You also can fetch users who have no assigned tasks:
SELECT
users.*
FROM
users
LEFT JOIN
user_tasks
ON (users.id = user_tasks.user_id)
WHERE
user_tasks.user_id IS NULL
Hope this will help you.