For example, there are three rooms.
1|gold_room|1,2,3
2|silver_room|1,2,3
3|brown_room|2,4,6
4|brown_room|3
5|gold_room|4,5,6
Then, I'd like to get
gold_room|1,2,3,4,5,6
brown_room|2,3,4,6
silver_room|1,2,3
How can I achieve this?
I've tried: select * from room group by name; And it only prints the first row. And I know CONCAT() can combine two string values.
Please use below query,
select col2, GROUP_CONCAT(col3) from data group by col2;
Below is the Test case,
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=ab35e8d66ffe3ac6436c17faf97ee9af
I'm not making an assumption that the lists don't have elements in common on separate rows.
First create a table of integers.
mysql> create table n (n int primary key);
mysql> insert into n values (1),(2),(3),(4),(5),(6);
You can join this to your rooms table using the FIND_IN_SET() function. Note that this cannot be optimized. It will execute N full table scans. But it does create an interim set of rows.
mysql> select * from n inner join rooms on find_in_set(n.n, rooms.csv) order by rooms.room, n.n;
+---+----+-------------+-------+
| n | id | room | csv |
+---+----+-------------+-------+
| 2 | 3 | brown_room | 2,4,6 |
| 3 | 4 | brown_room | 3 |
| 4 | 3 | brown_room | 2,4,6 |
| 6 | 3 | brown_room | 2,4,6 |
| 1 | 1 | gold_room | 1,2,3 |
| 2 | 1 | gold_room | 1,2,3 |
| 3 | 1 | gold_room | 1,2,3 |
| 4 | 5 | gold_room | 4,5,6 |
| 5 | 5 | gold_room | 4,5,6 |
| 6 | 5 | gold_room | 4,5,6 |
| 1 | 2 | silver_room | 1,2,3 |
| 2 | 2 | silver_room | 1,2,3 |
| 3 | 2 | silver_room | 1,2,3 |
+---+----+-------------+-------+
Use GROUP BY to reduce these rows to one row per room. Use GROUP_CONCAT() to put the integers together into a comma-separated list.
mysql> select room, group_concat(distinct n.n order by n.n) as csv
from n inner join rooms on find_in_set(n.n, rooms.csv) group by rooms.room
+-------------+-------------+
| room | csv |
+-------------+-------------+
| brown_room | 2,3,4,6 |
| gold_room | 1,2,3,4,5,6 |
| silver_room | 1,2,3 |
+-------------+-------------+
I think this is a lot of work, and impossible to optimize. I don't recommend it.
The problem is that you are storing comma-separated lists of numbers, and then you want to query it as if the elements in the list are discrete values. This is a problem for SQL.
It would be much better if you did not store your numbers in a comma-separated list. Store multiple rows per room, with one number per row. You can run a wider variety of queries if you do this, and it will be more flexible.
For example, the query you asked about, to produce a result with numbers in a comma-separated list is more simple, and you don't need the extra n table:
select room, group_concat(n order by n) as csv from rooms group by room
See also my answer to Is storing a delimited list in a database column really that bad?
ID| Date1 | Date 2 |Total
-----------------------------------
1 | 15/02/2017 |02/02/2017 | 3 |
-----------------------------------
1 | 15/02/2017 |05/08/2017 | 3 |
-----------------------------------
1 | 15/02/2017 |12/12/2017 | 3 |
-----------------------------------
2 | 12/05/2017 |07/08/2017 | 2 |
-----------------------------------
2 | 12/05/2017 |10/08/2017 | 2 |
I have a table that is displaying data like above. I'm grouping that data on "ID" column. Values for Columns "Date1" & "Total" for a particular "ID" are the same but "Date2" value can be different in a given group.
How can i merge the cells across rows when the values are the same such that it displays like below?
ID| Date1 | Date 2 |Total
-----------------------------------
1 | 15/02/2017 |02/02/2017 | 3 |
--| |------------| |
1 | |05/08/2017 | |
--| |------------| |
1 | |12/12/2017 | |
---------------------------------|
2 | 12/05/2017 |07/08/2017 | 2 |
--| |------------| |
2 | |10/08/2017 | |
I did manage to find that "HideDuplicates" TextBox property, but while that will suppress the repetition of the cell values in adjacent rows it does not merge those duplicate cells down the column across rows
Its difficult to tell how the report is setup in terms of groups etc without seeing the design, but this is pretty simple to do from scratch.
Start with a simple table with just your detail rows, no grouping. Then right-click the detail row in the row group panel under the main report design area. Choose Add Group -> Parent Group
Choose your Date1 field in the group by drop down . Click OK and you're done.
In Mysql, I have the following table:
id | paramname | paramcategory | value |
---+-------------+-------------------+-----------------+
1 | width | dimensions | 240 |
2 | height | dimensions | 400 |
3 | param1 | category1 | some value 1 |
4 | param2 | category1 | some value 2 |
5 | param3 | category10 | some value 100 |
...
I'd like to have a query that will return a table with only several rows concatenated, and all other rows should remain intact, something like this:
paramname | value |
--------------+--------------+
width, height | 240 x 400 |
param1 | some value 1 |
...
I'm thinking about concatenating based on the needed paramcategory, but if possible/needed, concatenation can happen for specific paramnames as well. Whatever is easier/simpler.
Any help please?
Looking at this problem from above, you are going to have to 'UNION' 2 queries together. The first part of the union is your concat'd results, the second your original rows. For the first part you are going to need to do a self join on this table, along the lines of
select concat(a.paramname, b.paramname), concat(a.value, b.value) from table a, table b where a.paramcategory = b.paramcategory
along those lines....
Actually if you swap the 2 parts of the union around, you'll keep the original column names too.
I'm wondering how to filter Hibernate results.
For example, I have this example table:
--------------------------------------------
| ID | STRING | DATE |
--------------------------------------------
| 1 | "ABC" | 2014-11-07 21:45:00 |
--------------------------------------------
| 2 | "ABC" | 2014-11-07 22:45:00 |
--------------------------------------------
| 3 | "DCE" | 2014-11-07 22:48:00 |
--------------------------------------------
| 4 | "ABC" | 2014-11-07 23:48:00 |
--------------------------------------------
The result that I need is:
--------------------------------------------
| ID | STRING | DATE |
--------------------------------------------
| 3 | "DCE" | 2014-11-07 22:48:00 |
--------------------------------------------
| 4 | "ABC" | 2014-11-07 23:48:00 |
--------------------------------------------
All lines of table, BUT, when I have the same content in column STRING, the column with the most recent DATE is the one in result set.
In hibernate I know
- select ALL lines;
- select the repeated lines and keep only the most recent.
But I don't know how to combine the two situations together, and I can't find it referenced anywhere.
I have a fixed length in STRING, and I use a fake primary key in my code to identify the register, but the value is inserted by user, and I have no previous knowledge of the content in the column.
You can do this using a not exists clause:
select e.*
from example e
where not exists (select 1 from example e2 where e2.string = e.string and e2.date > e.date);
That is, select all rows where there is no other row with the same string and a larger date.
I have table:
+----+--------+----------+
| id | doc_id | next_req |
+----+--------+----------+
| 1 | 1 | 4 |
| 2 | 1 | 3 |
| 3 | 1 | 0 |
| 4 | 1 | 2 |
+----+--------+----------+
id - auto incerement primary key.
nex_req - represent an order of records. (next_req = id of record)
How can I build a SQL query get records in this order:
+----+--------+----------+
| id | doc_id | next_req |
+----+--------+----------+
| 1 | 1 | 4 |
| 4 | 1 | 2 |
| 2 | 1 | 3 |
| 3 | 1 | 0 |
+----+--------+----------+
Explains:
record1 with id=1 and next_req=4 means: next must be record4 with id=4 and next_req=2
record4 with id=5 and next_req=2 means: next must be record2 with id=2 and next_req=3
record2 with id=2 and next_req=3 means: next must be record3 with id=1 and next_req=0
record3 with id=3 and next_req=0: means that this is a last record
I need to store an order of records in table. It's important fo me.
If you can, change your table format. Rather than naming the next record, mark the records in order so you can use a natural SQL sort:
+----+--------+------+
| id | doc_id | sort |
+----+--------+------+
| 1 | 1 | 1 |
| 4 | 1 | 2 |
| 2 | 1 | 3 |
| 3 | 1 | 4 |
+----+--------+------+
Then you can even cluster-index on doc_id,sort for if you need to for performance issues. And honestly, if you need to re-order rows, it is not any more work than a linked-list like you were working with.
Am able to give you a solution in Oracle,
select id,doc_id,next_req from table2
start with id =
(select id from table2 where rowid=(select min(rowid) from table2))
connect by prior next_req=id
fiddle_demo
I'd suggest to modify your table and add another column OrderNumber, so eventually it would be easy to order by this column.
Though there may be problems with this approach:
1) You have existing table and need to set OrderNumber column values. I guess this part is easy. You can simply set initial zero values and add a CURSOR for example moving through your records and incrementing your order number value.
2) When new row appears in your table, you have to modify your OrderNumber, but here it depends on your particular situation. If you only need to add items to the end of the list then you can set your new value as MAX + 1. In another situation you may try writing TRIGGER on inserting new items and calling similar steps to point 1). This may cause very bad hit on performance, so you have to carefully investigate your architecture and maybe modify this unusual construction.