I have been working with SQL joins and kinda stuck with following scenario:
Table 1: PK(ID, GRADE)
| ID | Grade | Student_Count |
| 1 | 10th | 20 |
| 1 | 9th | 20 || 2 | 10th | 20 || 2 | 9th | 20 |
Table 2:PK(ID, Grade, Visited_Date)
| ID | Grade | Visited | Visit_Date |
| 1 | 10th | Yes | 25-Dec-2015 |
| 1 | 10th | No | 26-Dec-2015 |
| 1 | 9th | Yes | 28-Dec-2015 |
| 1 | 9th | No | 29-Dec-2015 |
| 2 | 10th | Yes | 27-Dec-2015 |
| 2 | 9th | No | 30-Dec-2015 |
What i need is a SELECT query which returns data from both the tables for a given ID in such a way that output rows should match the data of the Table 2 (no all possible combinations like cross/dot product) along with non-common columns from Table 1.
For example for ID "1" the output should be:
| ID | Grade | Student_Count | Visited | Visit_date |
| 1 | 10th | 20 | Yes | 25-Dec-2015 |
| 1 | 10th | 20 | No | 26-Dec-2015 |
| 1 | 9th | 20 | Yes | 28-Dec-2015 |
| 1 | 9th | 20 | No | 29-Dec-2015 |
Note: There is no foreign key association between both the tables.
You have to JOIN both tables on the id and grade fields.
SELECT b.ID, b.Grade, a.Student_Count, b.Visited, b.Visit_date
FROM table2 b
INNER JOIN table1 a
ON a.ID = b.ID AND a.Grade = b.Grade
ORDER BY a.ID
Related
There are two tables,
Table A has a three-level structure that looks like
| id | name | level | up_level_id |
| :------- | :-------: | :------: | ----------:|
| 1 | lv1_name1 | 1 | null |
| 2 | lv1_name2 | 1 | null |
| 3 | lv2_name1 | 2 | 1 |
| 4 | lv2_name2 | 2 | 2 |
| 5 | lv3_name1 | 3 | 3 |
| 6 | lv3_name2 | 3 | 3 |
| 7 | lv3_name3 | 3 | 4 |
| 8 | lv3_name4 | 3 | 4 |
Table B looks like
| amount | org_id |
| -------- | -------- |
| 12,000 | 5 |
| 15,000 | 6 |
| 20,000 | 7 |
| 18,000 | 8 |
Table A and Table B can be joined on A.id=B.org_id, but they are all at the level-3 of Table A（Only level-3 has their amount）
I want to query the top-level name,level-1 name, and the summary amount that looks like
| sum_amount | top_lvl_name |
| -------- | -------- |
| 27,000 | lv1_name1 |
| 38,000 | lv1_name2 |
For Testing, I have already accomplished the query of the level-1 name from the level-3 id in TableA
The SQL is as follows
SELECT name
FROM TableA
WHERE id IN (
SELECT up_level_id
FROM Table A
WHERE id IN (
SELECT up_level_id
FROM Table A
WHERE id=5) --query the id:5's top-level name
);
But when I join these two tables as follows, it goes wrong
SELECT sum(amount) AS sum_amount, name AS top_lvl_name
FROM TableA, TableB
WHERE id = org_id
AND id IN (
SELECT up_level_id
FROM TableA
WHERE id IN (
SELECT up_level_id
FROM TableA
WHERE TableA.id IN(
SELECT org_id
FROM TABLEB
)
)
);
I get nothing as above
What can I do to make this query to be correct?
Thanks for everyone's answer and comment.
Finally, I find it very difficult to query the result as I wish. So, I've come up with a shortcut——create a new table that a three-level structure recorded horizontally, which looks like
| lv1_id | lv2_name | lv2_id | lv2_name | lv3_id | lv3_name |
| :------- | :-------: | :------: | :----------:| :------: | :----------:|
| 1 | lv1_name1 | 3 | lv2_name1 | 5 | lv3_name1 |
| 1 | lv1_name1 | 3 | lv2_name1 | 6 | lv3_name2 |
| 2 | lv1_name2 | 4 | lv2_name1 | 7 | lv3_name3 |
| 2 | lv1_name2 | 4 | lv2_name1 | 8 | lv3_name4 |
As above,I can easily connect two tables
Let's say i have a user table like this :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 8 | Joseph | psa.jos#mail.com | 34 |
| 9 | Joseph | joseph.la#mail.com | 28 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
In the actual, the database consists of more data and some of the data is duplicated, with more than two records. But the point is i want to get only the first and the second row of the duplicated rows that contains the name of "Joseph", How can i achieve this ? My code so far...
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 1')->get();
With that code the result will retrieve :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
And i use this code to try to get the second duplicated row :
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 2')->get();
The result is still same as the mentioned above :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
I want the result is to get record that have the id "5" with name "Joseph" like this :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 4 | George | gge.48#mail.com | 28 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
But it seems only the first duplicate row is retrieved and i can't get the second duplicated row, can anybody give me suggestion ?
Let's start from your query
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 1')->get();
This will show all groups of rows whose count equals to 1 ore more. and this is the description of DISTINCT.
If you want to get only duplicate records you should get groups whose count is LARGER than 1.
The other thing to notice here is that a non-aggrigated column will be chosen randomly. because when you get a name and it's count, for example if you select name,count(name), email (email is not in the group by clause - not aggregated), and 4 rows have the same name. so you'll see:
+--------+-------------+-------+
| Name | Count(Name) | Email |
+--------+-------------+-------+
| Joseph | 4 | X |
+--------+-------------+-------+
what do you expect instead of X? which one of the 4 emails? actually, in SQLServer it's forbidden to select a non-aggrigated column and other databases will just give you a random one of the counted 3.
see this answer for more details it's explained very well: Do all columns in a SELECT list have to appear in a GROUP BY clause
So, we'll use having count(name) > 1 and select only the aggregated column name
DB::from('users')->select('name')->groupBy('name')->havingRaw('count("name") > 1')->get();
This should give you (didn't test it) this:
+--------+-------------+
| name | Count(name) |
+--------+-------------+
| Joseph | 4 |
+--------+-------------+
This will give you all names who have 2 or more instances. you can determine the number of duplicates in the having clause. for example having count(name) = 3 will give you all names which have exactly 3 duplicates.
So how to get the second duplicate? I have a question for that:
What is the first (original) duplicate? is it the one with the oldest created_at or the oldest updated_at ? or maybe some other condition?. because of that you should make another query with order by clause to give you the duplicates in the order most convenient to you. for example:
select * from `users` where `name` in (select `name` from users group by `name` having count(`name`) > 1) order by `id` asc
which will give:
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 3 | Joseph | joseph410#mail.com | 21 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 8 | Joseph | psa.jos#mail.com | 34 |
| 9 | Joseph | joseph.la#mail.com | 28 |
+----+-----------+---------+------------+------+
I have two tables.
support_table
+------+-------------+
| num | num_explain |
+------+-------------+
| 1 | 01 |
| 2 | 01 |
| 2 | 02 |
| 3 | 01 |
| 3 | 02 |
| 3 | 03 |
| 4 | 01 |
| 4 | 02 |
| 4 | 03 |
| 4 | 04 |
| 5 | 01 |
| 5 | 02 |
| 5 | 03 |
| 5 | 04 |
| 5 | 05 |
+------+-------------+
class_room
+-----------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+-------------+------+-----+---------+-------+
| seq_no | varchar(20) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| subjects | varchar(20) | YES | | NULL | |
| no_of_student | varchar(20) | YES | | NULL | |
| student_roll_no | varchar(20) | YES | | NULL | |
+-----------------+-------------+------+-----+---------+-------+
Now I've tried the below query to insert data into table class_room:
INSERT INTO class_room (seq_no,name,subjects,no_of_student,student_roll_no)
SELECT '1', 'class11', 'physics', num, num_explain FROM support_table
WHERE num='3';
this query works totally fine for me and it creates 3 rows. Now the table looks like below:
+---------+---------+----------+---------------+-----------------+
| seq_no | name | subjects | no_of_student | student_roll_no |
+---------+---------+----------+---------------+-----------------+
| 1 | class11 | physics | 3 | 01 |
| 1 | class11 | physics | 3 | 02 |
| 1 | class11 | physics | 3 | 03 |
+---------+---------+----------+---------------+-----------------+
Now I want to update this table, so I've tried the below code:
UPDATE class_room
SET name='class11', subjects='chemistry', no_of_student =
(SELECT num_explain FROM support_table WHERE num='4')
WHERE seq_no='1';
But this query IS showing that
Subquery returns more than one row.
Here I want that in class_room table no_of_student will be changed to '4' and student_roll_no will be upto '04' and instead of 3 rows, 4 rows will be created.
You have 3 rows in the table but you expect finally to get 4 rows.
This can't be done with an UPDATE statement which does not add new rows.
The simplest way to do what you want is to delete the current rows and then insert:
delete from class_room where no_of_student = 3;
insert into class_room (seq_no,name,subjects,no_of_student,student_roll_no)
select '1', 'class11','chemistry',num,num_explain
from support_table
where num='4';
See the demo.
| seq_no | name | subjects | no_of_student | student_roll_no |
| ------ | ------- | --------- | ------------- | --------------- |
| 1 | class11 | chemistry | 4 | 1 |
| 1 | class11 | chemistry | 4 | 2 |
| 1 | class11 | chemistry | 4 | 3 |
| 1 | class11 | chemistry | 4 | 4 |
= Can be used when the subquery returns only 1 value.
When subquery returns more than 1 value, you will have to use IN :
UPDATE class_room set name='class11',subjects='chemistry',no_of_student IN (select num_explain FROM support_table WHERE num='4')LIMIT 1 WHERE seq_no='1';
Example :
select *
from table
where id IN (multiple row query);
Another example :
SELECT *
FROM Students
WHERE Marks = (SELECT MAX(Marks) FROM Students) --A Example Subquery returning 1 value
SELECT *
FROM Students
WHERE Marks IN
(SELECT Marks
FROM Students
ORDER BY Marks DESC
LIMIT 10) --Example Subquery returning 10 values
A good explanation can be found here by #Raging bull
I have a mysql table that holds data for team games.
Objective:
Count the number of times other SquadID's have have shared the same Team value as SquadID=21
// Selections table
+--------+---------+------+
| GameID | SquadID | Team |
+--------+---------+------+
| 1 | 5 | A |
| 1 | 7 | B |
| 1 | 11 | A |
| 1 | 21 | A |
| 2 | 5 | A |
| 2 | 7 | B |
| 2 | 11 | A |
| 2 | 21 | A |
| 3 | 5 | A |
| 3 | 7 | B |
| 3 | 11 | A |
| 3 | 21 | A |
| 4 | 5 | A |
| 4 | 11 | B |
| 4 | 21 | A |
| 5 | 5 | A |
| 5 | 11 | B |
| 5 | 21 | A |
| 6 | 5 | A |
| 6 | 11 | B |
| 6 | 21 | A |
+--------+---------+------+
// Desired Result
+---------+----------+
| SquadID | TeamMate |
+---------+----------+
| 5 | 6 |
| 7 | 0 |
| 11 | 3 |
| 21 | 6 |
+----------+---------+
I've attempted to use a subquery specifying the specific player I wish to compare with and because this subquery has multiple rows, I've used in instead of =.
// Current Query
SELECT
SquadID,
COUNT(Team IN (SELECT Team FROM selections WHERE SquadID=21) AND GameID IN (SELECT GameID FROM selections WHERE SquadID=21)) AS TeamMate
FROM
selections
GROUP BY
SquadID;
The result I'm getting is the number of Games a user has played rather than the number of games a user has been on the same team as SquadID=21
// Current Result
+---------+----------+
| SquadID | TeamMate |
+---------+----------+
| 5 | 6 |
| 7 | 3 |
| 11 | 6 |
| 21 | 6 |
+---------+----------+
What am I missing?
// DESCRIBE selections;
+---------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+-------+
| GameID | int(11) | NO | PRI | 0 | |
| SquadID | int(4) | NO | PRI | NULL | |
| Team | char(1) | NO | | NULL | |
| TeamID | int(11) | NO | | 1 | |
+---------+---------+------+-----+---------+-------+
General rule is to avoid nested selects and look for a better way of logically arranging joins. Lets look at a cross join:
From selections s1
inner join selects s2 on s1.gameid = s2.gameid and s1.team = s2.team
This will produce a cross joined list of each squadID that participated with another squadID (IE: they were in the same game and on same team). We are only interested in the times where the squad participated with squad 21, so add a where clause:
where s2.squadid = 21
Then it's simply choosing the field/count you want:
select s1.squad, count(1) as teammate
any aggregate needs a group by
group by s1.squad
Combine it together and give a go. Oddly, this will produce a list where squad 21 will be showing as playing on it's own team all 6 times. Adding a where clause can eliminate this
where s1.squadid <> s2.squadid
SELECT SquadID, count(t1.team) as TeamMate
FROM selections as t1 join
(select distinct team, gameid from selections where SquadID=21) as t2
on t1.Team=t2.Team and t1.Gameid=t2.Gameid
GROUP BY SquadID
I have a table that has some values in it, along with the time that value was taken against an associated ID from another table.
I am looking to retrieve the latest value for every item in that table, and then order by those latest values.
Here is an SQL fiddle, http://www.sqlfiddle.com/#!2/0be99
And here is text output.
'hist' table
| HIST_ID | HIST_ITEM_ID | HIST_VALUE | HIST_TIME |
|---------|--------------|------------|------------|
| 1 | 1 | 1 | 1420291000 |
| 2 | 1 | 2 | 1420292000 |
| 3 | 1 | 3 | 1420293000 |
| 4 | 1 | 5 | 1420294000 |
| 5 | 1 | 10 | 1420295000 |
| 6 | 1 | 50 | 1420296000 |
| 7 | 1 | 60 | 1420297000 |
| 8 | 1 | 77 | 1420298000 |
| 9 | 1 | 90 | 1420299000 |
| 10 | 1 | 101 | 1420300000 |
| 11 | 2 | 1 | 1420291000 |
| 12 | 2 | 3 | 1420292000 |
| 13 | 2 | 7 | 1420293000 |
| 14 | 2 | 9 | 1420294000 |
| 15 | 2 | 15 | 1420295000 |
| 16 | 2 | 21 | 1420296000 |
| 17 | 2 | 33 | 1420297000 |
| 18 | 2 | 35 | 1420298000 |
| 19 | 2 | 55 | 1420299000 |
| 20 | 2 | 91 | 1420300000 |
'items' table
| ITEM_ID | ITEM_TITLE |
|---------|------------|
| 1 | ABCD |
| 2 | XYZ123 |
So, I can do something like...
select * from hist
inner join items on hist_item_id = item_id
group by hist_item_id
order by hist_value desc
However this returns me a grouping that I cannot order. How can I order this grouping? I had a look at other similar questions on here but was unable to apply their solutions successfully to my query to produce the desire result.
The desired result here would be to return.
HIST_ITEM_ID | ITEM_TITLE | HIST_VALUE |
|------------|------------|------------|
| 1 | ABCD | 101 |
| 2 | XYZ123 | 91 |
You can use a join to get the most recent history item. Then you can join back to the history table and the item table to get additional information:
select h.*, i.item_title
from (select hist_item_id, max(hist_id) as max_hist_id
from hist
group by hist_item_id
) hh join
hist h
on h.hist_id = hh.max_hist_id join
items i
on i.item_id = hh.hist_item_id;
Here is a SQL Fiddle.
You should use MAX function and group by the item id. That would look like this:
SELECT i.item_id, i.item_title, MAX(h.hist_value)
FROM items AS i
INNER JOIN hist AS h
ON i.item_id = h.hist_item_id
GROUP BY i.item_id