I have a column of data, e.g. as follows:
select league_id from leagues
This gives me a single column (league_id) and 100+ rows for that column.
I want to convert it into a single cell (1 row, 1 column) with the following structure:
[1001, 1002, 42022, 203412, 24252, etc..]
Essentially converting the rows into one big array.
There must be a way of doing it but can't see how.
I'm using MariaDB 10.2.
You can use the GROUP_CONCAT() function for that.
Usage is straightforward:
id
val
1
1001
2
1002
3
42022
4
203412
5
24252
SELECT group_concat(val)
FROM tab
gives you
group_concat(val)
1001,1002,42022,203412,24252
See db<>fiddle.
(Note: Before MariaDB 10.3.3 you cannot use the LIMIT clause with GROUP_CONCAT, in case you should need that).
Related
I want to select all package_id that contain product_id 2.
In this case, package_id 1,3,5 has product_id 2
Table: product_package
package_id package_name product_id
---------------------------------------------
1 Gold 1,2,3
2 Platinum 4,5,12
3 Diamond 2,11,5
4 Titanium 3,5
5 Basic 2
I tried:
SELECT
*
FROM
product_package
WHERE product_id IN(2)
It is outputting package_id 3 and 5 only. How do I output this properly?
product_id structure is varchar(256). Should I change the structure or add Foreign keys?
We always recommend not to stored delimited columns see Is storing a delimited list in a database column really that bad?
But you can use FIND_IN_SET but this is always slow
SELECT
*
FROM
product_package
WHERE FIND_IN_SET(2,product_id)
package_id
package_name
product_id
1
Gold
1,2,3
3
Diamond
2,11,5
5
Basic
2
fiddle
First, let me explain what is happening in your query.
You have WHERE product_id IN(2), but product_id is a misnomer and should rather be product_ids, because it is multiple IDs unfortunately stored in a string. IN is made to look up a value in a list. Your list, however, only consists of one element, so you can just as well use the equality operator: WHERE product_id = 2.
What you have is WHERE string = number, so the DBMS has to convert one of the values in order to compare the two. It converts the string to a number (so '2' matches 2 and '002' matches 2, too, as it should). But your strings are not numbers. The DBMS should raise an error on '1,2,3' for instance, because '1,2,3' is not a number. MySQL, however, has a design flaw here and still converts the string, regardless. It just takes as many characters from the left as they still represent a number. '1' does, but then the comma is not considered numerical (yes, MySQL cannot deal with a thousand separator when convertings strings to numbers implicitly). So converting '1,2,3' to a number results in 1. Equally, '2,11,5' results in 2, so rather surprisingly '2,11,5' = 2 in MySQL. This is why you are getting that row.
You ask "Should I change the structure", and the answer to this is yes. So far your table doesn't comply with the first normal form and should thus not exist in a relational database. You'll want two tables instead forming the 1:n relation:
Table: package
package_id
package_name
1
Gold
2
Platinum
3
Diamond
4
Titanium
5
Basic
Table: product_package
package_id
product_id
1
1
1
2
1
3
2
4
2
5
2
12
3
2
3
11
3
5
4
3
4
5
5
2
You ask "or add Foreign keys?", and the answer is and add foreign keys. So with the changed structure you want product_package(product_id) to reference product(product_id) and product_package(package_id) to reference package(package_id).
Disregarding that you should not be storing multiple values in a single field, you can use LIKE operator to achieve what you are looking for. I'm going with assumptions:
all values are delimited with commas
all values are integers
there are no whitespaces (or any other characters besides integers and commas)
select * from product_package
where product_id like '2,%'
or product_id like '%,2,%'
or product_id like '%,2'
or product_id like '2'
Alternatively, you can use REGEXP operator:
select * from product_package
where product_id regexp '^2$|^2,.+|.+,2,.+|.+,2'
References:
MySQL LIKE
MySQL REGEXP
I want to get the data after the row with a certain string. I think I will explain it better with the following example. Below is a mysql table.
-id- -name(unique)-
1 Test
2 Test2
3 Test3
4 Test4
Here, for example, I want to get the data after the row with the name 'Test2'. Is it possible to do this in one query with mysql? (By pulling the id of the row with that data and not using it as an offset.)
It should give the following result as a result.
-id- -name-
3 Test3
4 Test4
I searched but couldn't find it or I couldn't understand how to search. Can you help?
You basically need to use LIMIT and OFFSET. Since you don't know the number of rows you want to have in you result, you can set limit to a high number. Something like
SELECT
*
FROM
TABLE1 t
LIMIT 9999999999
OFFSET 2
OFFSET value can be set to whatever number of rows you want to exclude from your result.
Or as per your question if you don't want to use OFFSET, use a subquery to determine the id
SELECT
*
FROM
TABLE1 t
WHERE
t.id>(SELECT t1.id FROM TABLE1 t1 WHERE t1.name='Test2')
I have a table (t1) in mySQL that generates the following table:
type time full
0 11 yes
1 22 yes
0 11 no
3 13 no
I would like to create a second table (t2) from this that will summarize the information found in t1 like the following:
type time num_full total
0 11 1 2
1 22 1 1
3 13 0 1
I want to be able to iterate through the type column in order to be able to start this summary, something like a for-loop. The types can be up to a value of n, so I would rather not write n+1 WHERE statements, then have to update the code every time more types are added.
Notice how t2 skipped the type of value 2? This has also been escaping me when I try looping. I only want the the types found to have rows created in t2.
While a direct answer would be nice, it would be much more helpful to be pointed to some sources where I could figure this out, or both.
This may do what you want
create table t2 if not exists select type, time, sum(full) num_full, count(*) count
from t1
group by type,time
order by type,time;
depending on how you want to aggregate the time column.
This is a starting point for reference on the group by functions : https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html
here for create syntax
https://dev.mysql.com/doc/refman/5.6/en/create-table.html
I have a database table as below.
Promotion_Table
id(INT), promotion_name(VARCHAR),......, bungalow_ids(VARCHAR)
We can add a promotion for a bungalow(23). So a row is added with the bungalow id as below.
1, My Promotion, ........, 23
But if I single a promotion is added for a multiple bungalows(23,42) all ids are saved in the bungalow_ids column as below.
2, My Promotion 2, ........, 23 | 42
If a user search for promotion which are for specific bungalow(23) All promotions for the bungalow should be shown in the result.
I have a query as below.
SELECT * FROM Promotion_Table WHERE bungalow_ids = '23'
It only gets 1 rows. But actually 2nd row should be shown too since there is a offer. I can nt use LIKE since it gets wrong records.
Given that I have already referred below links but I have no idea how to use them in the query.
Can you split/explode a field in a MySQL query?
Equivalent of explode() to work with strings in MySQL
How can I fix this? How can I explode the column data and use it in the query ?
Use , to separate the string and try this query
select * from promotion_table where FIND_IN_SET("23",bungalow_ids)
http://sqlfiddle.com/#!2/7bbcb/1
The previous Answer is the right decision but if you insist in your model.
Probably what you want to do is:
SELECT *
FROM Promotion_Table
WHERE bungalow_ids = '23'
OR bungalow_ids LIKE '23,*'
OR bungalow_ids LIKE '*,23'
OR bungalow_ids LIKE '*,23,*'
this assuming the numbers are separated by ",".
But this is the wrong way, make the changes to the DB as stated in the previous answer.
you need to reformat your DB schema.
you need to construct 2 tables one for promotions and one for bangalows.
like below:
promotions: Promotion_id(int), Promotion_desc
bangalows: Bangalow_id(int), Promotion_id(int)
tables example:
promotion :
1 myPromotion
2 secondPromotion
bangalows:
1 1
2 2
3 1
4 1
once you create above two tables, the following query will work and returns 1,3,4:
SELECT Bangalow_id FROM Promotion_Table WHERE bungalow_id = '1'
I have some strings in my database. Some of them have numeric values (but in string format of course). I am displaying those values ordered ascending.
So we know, for string values, 10 is greater than 2 for example, which is normal. I am asking if there is any solution to display 10 after 2, without changing the code or the database structure, only the data.
If for example I have to display values from 1 to 10, I will have:
1
10
2
3
4
5
6
7
8
9
What I would like to have is
1
2
3
4
5
6
7
8
9
10
Is there a possibility to ad an "invisible character or string which will be interpreted as greater than 9". If i put a10 instead of 10, the a10 will be at the end but is there any invisible or less visible character for that.
So, I repeat, I am not looking for a programming or database structure solution, but for a simple workaround.
You could try to cast the value as an number to then order by it:
select col
from yourtable
order by cast(col AS UNSIGNED)
See SQL Fiddle with demo
You could try appending the correct number of zeroes to the front of the data:
01
02
03
..
10
11
..
99
Since you have a mixture of numbers and letters in this column - even if not in a single row - what you're really trying to do is a Natural Sort. This is not something MySQL can do natively. There are some work arounds, however. The best I've come across are:
Sort by length then value.
SELECT
mixedColumn
FROM
tableName
ORDER BY
LENGTH(mixedColumn), mixedColumn;
For more examples see: http://www.copterlabs.com/blog/natural-sorting-in-mysql/
Use a secondary column to use as a sort key that would contain some sort of normalized data (i.e. only numbers or only letters).
CREATE TABLE tableName (mixedColumn varchar, sortColumn int);
INSERT INTO tableName VALUES ('1',1), ('2',2), ('10',3),
('a',4),('a1',5),('a2',6),('b1',7);
SELECT
mixedColumn
FROM
tableName
ORDER BY
sortColumn;
This could get difficult to maintain unless you can figure out a good way to handle the ordering.
Of course if you were able to go outside of the database you'd be able to use natural sort functions from various programming languages.