I have a some entries in database table rows as follows.
101 - 1
101 - 2
101 - 3
102 - 1
102 - 2
102 - 3
103
I need to get the result of SELECT Query for count as '3' since there are 101 and 102 are the only number before the -.
So is there any way to find the unique value in db table columns before a character?
EDIT : I have entries even without the - .
In case your entries have always the format you have provided us, you just have to find the position of the '-' character, split the values, get the first n characters and count the distinct values
This works for SQL Server, otherwise informs us about what DBMS you are using or replace the functions with the ones of your DBMS on your own
SELECT COUNT(DISTINCT SUBSTRING(val,0,CHARINDEX('-', val))) from YourTable
create table T1
(
id int primary key identity,
col1 varchar(20)
)
insert into T1 values('101 - 1'),('101 - 2'),('101 - 3'),('102 - 1'),('102 - 2'),('102 - 3')
select SUBSTRING(col1,0,CHARINDEX(' ',col1)) as 'Value',count(*) as 'Count' from T1 group by SUBSTRING(col1,0,CHARINDEX(' ',col1))
Related
I have this query :
select
name
from
provinces
WHERE
province_id IN(1,3,2,1)
ORDER BY FIELD(province_id, 1,3,2,1)
the Number of values in IN() are dynamic
How can I get all rows even duplicates ( in this example -> 1 ) with given ORDER BY ?
the result should be like this :
name1
name3
name2
name1
plus I shouldn't use UNION ALL :
select * from provinces WHERE province_id=1
UNION ALL
select * from provinces WHERE province_id=3
UNION ALL
select * from provinces WHERE province_id=2
UNION ALL
select * from provinces WHERE province_id=1
You need a helper table here. On SQL Server that can be something like:
SELECT name
FROM (Values (1),(3),(2),(1)) As list (id) --< List of values to join to as a table
INNER JOIN provinces ON province_id = list.id
Update: In MySQL Split Comma Separated String Into Temp Table can be used to split string parameter into a helper table.
To get the same row more than once you need to join in another table. I suggest to create, only once(!), a helper table. This table will just contain a series of natural numbers (1, 2, 3, 4, ... etc). Such a table can be useful for many other purposes.
Here is the script to create it:
create table seq (num int);
insert into seq values (1),(2),(3),(4),(5),(6),(7),(8);
insert into seq select num+8 from seq;
insert into seq select num+16 from seq;
insert into seq select num+32 from seq;
insert into seq select num+64 from seq;
/* continue doubling the number of records until you feel you have enough */
For the task at hand it is not necessary to add many records, as you only need to make sure you never have more repetitions in your in condition than in the above seq table. I guess 128 will be good enough, but feel free to double the number of records a few times more.
Once you have the above, you can write queries like this:
select province_id,
name,
#pos := instr(#in2 := insert(#in2, #pos+1, 1, '#'),
concat(',',province_id,',')) ord
from (select #in := '0,1,2,3,1,0', #in2 := #in, #pos := 10000) init
inner join provinces
on find_in_set(province_id, #in)
inner join seq
on num <= length(replace(#in, concat(',',province_id,','),
concat(',+',province_id,',')))-length(#in)
order by ord asc
Output for the sample data and sample in list:
| province_id | name | ord |
|-------------|--------|-----|
| 1 | name 1 | 2 |
| 2 | name 2 | 4 |
| 3 | name 3 | 6 |
| 1 | name 1 | 8 |
SQL Fiddle
How it works
You need to put the list of values in the assignment to the variable #in. For it to work, every valid id must be wrapped between commas, so that is why there is a dummy zero at the start and the end.
By joining in the seq table the result set can grow. The number of records joined in from seq for a particular provinces record is equal to the number of occurrences of the corresponding province_id in the list #in.
There is no out-of-the-box function to count the number of such occurrences, so the expression at the right of num <= may look a bit complex. But it just adds a character for every match in #in and checks how much the length grows by that action. That growth is the number of occurrences.
In the select clause the position of the province_id in the #in list is returned and used to order the result set, so it corresponds to the order in the #in list. In fact, the position is taken with reference to #in2, which is a copy of #in, but is allowed to change:
While this #pos is being calculated, the number at the previous found #pos in #in2 is destroyed with a # character, so the same province_id cannot be found again at the same position.
Its unclear exactly what you are wanting, but here's why its not working the way you want. The IN keyword is shorthand for creating a statement like ....Where province_id = 1 OR province_id = 2 OR province_id = 3 OR province_id = 1. Since province_id = 1 is evaluated as true at the beginning of that statement, it doesn't matter that it is included again later, it is already true. This has no bearing on whether the result returns a duplicate.
I have field Serial_No which just count serial no of student i used
identity(1,1)
But Problem is that if i delete row/rows it not decrease the Serial_No like
Serial_No Name Marks
1 Ehsan 50
3 Nouman 40
9 ejaz 56
10 ali 30
11 saleem 78
15 abdullah 90
.... ..... ....
... .. .....
I need Serial_No auto increment but also update after delete and insert row
like 1,2,3,4,5,6,7,8,9,10,11,..........
SQL Server answer here since both are tagged in post. I would say to leave your Identity column alone. Let it perform the way it is designed. Instead, create a view that selects all your columns and also includes a window function (row_number) to generate your sequential list you are looking for.
CREATE VIEW view_YourTable AS (
select *
, ROW_NUMBER() OVER(order by serial_no) AS sequential_id
FROM your_table);
SELECT *
FROM view_YourTable
I am trying to write a pivot function in MySQL workbench and many of the places I've looked have not been super relevant.
I currently have:
order_ID Part Description Order number
1 103 A 1
2 104 B 1
3 103 A 2
4 105 C 3
5 103 A 4
6 105 C 4
7 107 D 4
I would like to create:
Order Part1 Description Part2 Description Part3 Description
1 103 A 104 B
2 103 A
3 105 C
4 103 A 105 C 107 D
I can keep the primary key in the output, but it is not necessary. The problem I am running into is that many pivot functions involve using distinct parts names to move them; however, I have over 500 parts. I also would like to move the description and the part together so they are next to each other--most pivot functions are not powerful enough to address that.
I did write a macro to do this in Excel, but it must be done in a database because of further analysis in R and I am pulling data from a database and I must automate any changes made to the data. As a result, I DO NOT have a choice in how the data is organized and laid out. Please do not mention normalizing data or other database techniques because I am trying to fix the data and how messy it is, but I DO NOT have a choice in how the data is inputted.
Some resources I used to gain experience with pivoting in MySQL, but I have not been able to get any code to work.
MySQL pivot table
mysql pivoting - how can I fetch data from the same table into different columns?
http://en.wikibooks.org/wiki/MySQL/Pivot_table
http://buysql.com/mysql/14-how-to-automate-pivot-tables.html
Select group_concat(Table.column1) as anything,
group_concat(Table.column2 separator ';')
AS Anything2, Table.`column3`
FROM Table
group by Table.column3;
Alter TABLE Table ADD
`newcolumn1` varchar(100) DEFAULT '' after `column3`;
Alter TABLE MB ADD
`newcolumn2` varchar(500) DEFAULT '' after `newcolumn1`;
UPDATE Table SET
`newcolumn1` = IF (
LOCATE(',', column1) >0,
SUBSTRING(column1, 1,LOCATE(',', column1)-1),
column1
),
`newcolumn2` = IF(
LOCATE(',', column1) > 0,
SUBSTRING(column1, LOCATE(',', column1)+1),
'');
UPDATE Table SET
newcolumn2 = SUBSTRING_INDEX(newcolumn2, ',', 1);
UPDATE Table SET
newcolumn3 = SUBSTRING_INDEX(newcolumn3, ',', 1);
This code achieved exactly the format I wanted above.
I'm fairly sure this is a fairly easy answer but the answer is completely slipping my mind.
I have a database table that is currently formatted like:
event_id | elem_id | value
1 1 Value 1
1 2 Value 2
2 1 Value 3
2 2 Value 4
Both event_id and elem_id are undetermined numbers and have infinite possibilities.
How would I query it for example based on event_id 1 to get the data to be formatted as such:
event_id | 1 | 2
1 Value 1 Value 2
Knowing that elem_id is a number >= n so potentially there could be 50 elem_id yet I still need the data in that format.
Like I said I can't for the life of me figure out the query to assemble it that way. Any help would be GREATLY appreciated.
Try following:
SELECT
`event_id`,
(SELECT t2.`value` FROM table t2 WHERE t2.`event_id` = t1.`event_id` AND t2.`elem_id` = 1),
(SELECT t3.`value` FROM table t3 WHERE t3.`event_id` = t1.`event_id` AND t3.`elem_id` = 2)
FROM `table` t1 GROUP BY `event_id`;
Also you can use different way, and get elem_ids and values in comma-separated format in two cells
SELECT `event_id`, GROUP_CONCAT(`elem_id`), GROUP_CONCAT(`value`) FROM `table` GROUP BY `event_id`;
and you can change separator with following syntax: GROUP_CONCAT(field SEPARATOR '::')
when I DELETE, as example, the id 3, I have this:
id | name
1 |
2 |
4 |
5 |
...
now, I want to search for the missing id(s), because i want to fill the id again with:
INSERT INTO xx (id,...) VALUES (3,...)
is there a way to search for "holes" in the auto_increment index?
thanks!
You can find the top value of gaps like this:
select t1.id - 1 as missing_id
from mytable t1
left join mytable t2 on t2.id = t1.id - 1
where t2.id is null
The purpose of AUTO_INCREMENT is to generate simple unique and meaningless identifiers for your rows. As soon as you plan to re-use those IDs, they're no longer unique (not at least in time) so I have the impression that you are not using the right tool for the job. If you decide to get rid of AUTO_INCREMENT, you can do all your inserts with the same algorithm.
As about the SQL code, this query will match existing rows with the rows that has the next ID:
SELECT a.foo_id, b.foo_id
FROM foo a
LEFT JOIN foo b ON a.foo_id=b.foo_id-1
E.g.:
1 NULL
4 NULL
10 NULL
12 NULL
17 NULL
19 20
20 NULL
24 25
25 26
26 27
27 NULL
So it's easy to filter out rows and get the first gap:
SELECT MIN(a.foo_id)+1 AS next_id
FROM foo a
LEFT JOIN foo b ON a.foo_id=b.foo_id-1
WHERE b.foo_id IS NULL
Take this as a starting point because it still needs some tweaking:
You need to consider the case where the lowest available number is the lowest possible one.
You need to lock the table to handle concurrent inserts.
In my computer it's slow as hell with big tables.
I think the only way you can do this is with a loop:
Any other solutions wont show gaps bigger than 1:
insert into XX values (1)
insert into XX values (2)
insert into XX values (4)
insert into XX values (5)
insert into XX values (10)
declare #min int
declare #max int
select #min=MIN(ID) from xx
select #max=MAX(ID) from xx
while #min<#max begin
if not exists(select 1 from XX where id = #min+1) BEGIN
print 'GAP: '+ cast(#min +1 as varchar(10))
END
set #min=#min+1
end
result:
GAP: 3
GAP: 6
GAP: 7
GAP: 8
GAP: 9
First, I agree with the comments that you shouldn't try filling in holes. You won't be able to find all the holes with a single SQL statement. You'll have to loop through all possible numbers starting with 1 until you find a hole. You could write a sql function to do this for you that could then be used in a function. So if you wrote a function called find_first_hole you could then call it in an insert like:
INSERT INTO xx (id, ...) VALUES (find_first_hole(), ...)
This is a gaps&island problem, see my (and other) replies here and here. In most cases, gaps&islands problems are most elegantly solved using recursive CTE's, which are not available in mysql.