I am working with Codeigniter and its Query Builder class where I have a table with IDs and names.
Those names look like 1234_1a or 2345_2a where 1a can be 1b or 2a,2b,3a... and so on.
Now I want to count all these "1234" and "2345" but write them as one type.
So far I tried with:
$this->db->like('names', '1a', 'before');
$this->db->or_like('names', '1b', 'before');
return $this->db->count_all_results('table');
But the problem:
What if there is 3456_2a but no 3456_1a, than it doesn't work anymore...
id name
2 1212_1a
3 1243_1a
7 3142_1a
24 1243_2a
30 3142_2b
80 2315_2b
136 1243_3b
512 8562_1a
This is how I would like it:
Result:
name count
1212 1
1243 1
3142 1
2315 1
8562 1
If we always want to return a count value of 1, when the count of the number of rows in more than 1 ... then we aren't really returning a count.
And what is the pattern of the names... do they end with a digit and a letter, or is that underscore character important too?
What is to be done with name values such as 12345a or 5678_b2 or 11_22_3b? How are those to be handled?
Seems to me like we want to use a SQL query like this:
SELECT SUBSTRING_INDEX(t.name,'_',1) AS `foo`
, 1 AS `count`
FROM (
SELECT 2 AS `id`, '1212_1a' AS `name`
UNION ALL SELECT 3, '1243_1a'
UNION ALL SELECT 7, '3142_1a'
UNION ALL SELECT 24, '1243_2a'
UNION ALL SELECT 30, '3142_2b'
UNION ALL SELECT 80, '2315_2b'
UNION ALL SELECT 136, '1243_3b'
UNION ALL SELECT 512, '8562_1a'
) t
GROUP BY `foo`
ORDER BY `foo`
The inline view (derived table) is in the query for testing. Replace that with the table reference:
SELECT SUBSTRING_INDEX(t.name,'_',1) AS `foo`
, 1 AS `count`
FROM mytable t
GROUP BY `foo`
ORDER BY `foo`
The expression for foo may need to be adjusted, to get desirable behavior with values that don't follow the regular pattern. Consider name values with no underscore, with more than one underscore, with endings other than a digit. We could also include a WHERE clause to exclude rows that don't follow the pattern,
WHERE t.name REGEXP '_[0-9][a-z]$'
(only name values that end with underscore, digit, lowercase letter).
Without a tested SQL query, I wouldn't know what to implement in CodeIgniter Query Builder.
Related
I have requirement like as below.
Need a MYSQL query to replace value with maching the below condition.
i have a table containg the Product ID
Product_ID
1
2
3
4
5
15
25
I want to replace the 5 with value of 1.111. My requiremnet is this that it should only replace the 5 value not the 15 value.
example 5 should be 1.111 but it sould not replace the 15 value.
You can use IF() or CASE to select a different value when the value meets a condition.
SELECT IF(product_id = '5', '1.111', product_id)
FROM yourTable
or
SELECT CASE product_id
WHEN '5' THEN '1.111'
ELSE product_id
END
FROM yourTable
CASE generalizes more easily to other values that you want to replace, since you can have multiple WHEN clauses.
I want to get data from table where Id should be as given below in the query but instead of or I would apply and operator so lets say ID IN (5 AND 4 AND 3)
SELECT * FROM table WHERE id IN (5,4,3,1,6)
Is it possible to get data like this.
This is the sample query
SELECT PM.ContentID, PM.Author, PM.Title, PM.Journal, PM.Year, PM.Category, PM.StudyLocation, PM.FileURL from PublishedContentMaster PM join TopicContentMapping T ON T.ContentID=PM.ContentID where PM.ContentID='100' AND T.TopicID IN (16,7)
So I want which is present in both 16 and 17 that is why I need and operator not or.
I suspect that you want an aggregation query and a having clause. It would typically look something like this:
select x
from t
where id in (5, 4, 3, 1, 6)
group by x
having count(*) = 5;
In this case, x would be the column where you want five rows with the five values.
Hey guys i have did some coding in mysql to add a new line value to a row..
SELECT
babe
FROM
(SELECT
concat_ws(' ', 'assword \n') AS babe,
) test;
When i did like this i get an output like
BABE
assword name
What i need is an output like
BABE
assword
name(this would be below assword)
Is there any mysql functions to do this ??...or can i UPDATE the row ??..
I am a newbie in mysql. Hope you guys can help me out..Thanks in advance..
The statement includes a newline character in the babe column. You can confirm this by using the HEX() function to view the character encodings.
For example:
SELECT HEX(t.babe)
FROM ( SELECT CONCAT_WS(' ', 'assword \n') AS babe ) t
On my system, that Will output:
617373776F7264200A
It's easy enough to understand what was returned
a s s w o r d \n
61 73 73 77 6F 72 64 20 0A
(In the original query, there's an extraneous comma that will prevent the statement from running. Perhaps there was another expression in the SELECT list of the inline view, and that was returning the 'name' value that's shown in the example output. But we don't see any reference to that in the outer query.
It's not clear why you need the newline character. If you want to return:
BABE
-----------
asssword
name
That looks like two separate rows to me. But it's valid (but peculiar) to do this:
SELECT t.babe
FROM ( SELECT CONCAT_WS(' ', 'assword \nname') AS babe ) t
FOLLOWUP
Q: i just wanted to know how to add a new row below the assword ..if u know please edit the answer
It's not clear what result you are trying to achieve. The specification, divorced from the context of a use-case, is just bizarre.
A: If I had a need to return two rows: one row with the literal 'assword' and another row "below" it with the literal 'name', I could do this:
( SELECT 'assword' AS some_string )
UNION ALL
( SELECT 'name' AS some_string )
ORDER BY some_string
In this particular case, we can get the ordering we need by a simple reference to the column in the ORDER BY clause.
In the more general case, when there isn't a convenient expression for the ORDER BY clause, I would add an additional column, and perform a SELECT on the resultset from the UNION ALL operation. In this example, that "extra" column is named seq:
SELECT t.some_string
FROM ( SELECT 'assword' AS some_string, 1 AS seq
UNION ALL SELECT 'name', 2
)
ORDER BY t.seq
As another example:
( SELECT 'do' AS tone, 1 AS seq )
UNION ALL ( SELECT 're', 2 )
UNION ALL ( SELECT 'mi', 3 )
UNION ALL ( SELECT 'fa', 4 )
ORDER BY seq
I'd only need to add an outer SELECT if I needed a projection operation (for example, to remove the seq column from the returned resultset.
SELECT t.tone
FROM ( SELECT 'do' AS tone, 1 AS seq
UNION ALL SELECT 're', 2
UNION ALL SELECT 'mi', 3
UNION ALL SELECT 'fa', 4
)
ORDER BY t.seq
For experimental purposes only.
I would like to build a query but not querying data extracted for any table but querying data provided in the query it self. Like:
select numbers.* from (1, 2, 3) as numbers;
or
select numbers.* from (field1 = 1, field2 = 2, field3 = 3) as numbers;
so I can do things like
select
numbers.*
from (field1 = 1, field2 = 2, field3 = 3) as numbers
where numbers.field1 > 1;
If the solution is specific for a database engine could be interesting too.
If you wanted the values to be on separate rows instead of three fields of the same row, the method is the same, just one row per value linked with a union all.
select *
from(
select 1 as FieldName union all
select 2 union all
select 3 union all
select 4 union all -- we could continue this for a long time
select 5 -- the end
) as x;
select numbers.*
from(
select 1 ,2, 3
union select 3, 4, 5
union select 6, 7, 8
union select 9, 10, 11 -- we could continue this for a long time
union select 12, 13, 14 -- the end
) as numbers;
This works with MySQL and Postgres (and most others as well).
[Edit] Use union all rather than just union as you do not need to remove duplicates from a list of constants. Give the field(s) in the first select a meaningful name. Otherwise, you can't specify a specific field later on: where x.FieldName = 3.
If you don't provide meaningful names for the fields (as in the second example), the system (at least MySQL where this was tested) will assign the name "1" for the first field, "2" as the second and so on. So, if you want to specify one of the fields, you have to write expressions like this:
where numbers.1 = 3
Use the values row constructor:
select *
from (values (1),(2),(3)) as numbers(nr);
or using a CTE.
with numbers (nr) as (
values (1),(2),(3)
)
select *
from numbers
where nr > 2;
Edit: I just noticed that you also taggeg your question with mysql: the above will not work with MySQL, only with Postgres (and a few other DBMS)
You can use a subquery without table like so:
SELECT
numbers.*
FROM (
SELECT
1 AS a,
2 AS b,
3 AS c
UNION
SELECT
4,
5,
6
) AS numbers
WHERE
numbers.a > 1
If you like queries to always have a table referenced there is a Psuedo table that always has 1 row and no columns called DUAL, you can use it like so:
SELECT
numbers.*
FROM (
SELECT
1 AS a,
2 AS b,
3 AS c
FROM
DUAL
UNION
SELECT
4,
5,
6
FROM
DUAL
) AS numbers
WHERE
numbers.a > 1
I have a mysql table which contains some random combination of numbers. For simplicity take the following table as example:
index|n1|n2|n3
1 1 2 3
2 4 10 32
3 3 10 4
4 35 1 2
5 27 1 3
etc
What I want to find out is the number of times a combination has occured in the table. For instance, how many times has the combination of 4 10 or 1 2 or 1 2 3 or 3 10 4 etc occured.
Do I have to create another table that contains all possible combinations and do comparison from there or is there another way to do this?
For a single combination, this is easy:
SELECT COUNT(*)
FROM my_table
WHERE n1 = 3 AND n2 = 10 AND n3 = 4
If you want to do this with multiple combinations, you could create a (temporary) table of them and join that table with you data, something like this:
CREATE TEMPORARY TABLE combinations (
id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
n1 INTEGER, n2 INTEGER, n3 INTEGER
);
INSERT INTO combinations (n1, n2, n3) VALUES
(1, 2, NULL), (4, 10, NULL), (1, 2, 3), (3, 10, 4);
SELECT c.n1, c.n2, c.n3, COUNT(t.id) AS num
FROM combinations AS c
LEFT JOIN my_table AS t
ON (c.n1 = t.n1 OR c.n1 IS NULL)
AND (c.n2 = t.n2 OR c.n2 IS NULL)
AND (c.n3 = t.n3 OR c.n3 IS NULL)
GROUP BY c.id;
(demo on SQLize)
Note that this query as written is not very efficient due to the OR c.n? IS NULL clauses, which MySQL isn't smart enough to optimize. If all your combinations contain the same number of terms, you can leave those out, which will allow the query to make use of indexes on the data table.
Ps. With the query above, the combination (1, 2, NULL) won't match (35, 1, 2). However, (NULL, 1, 2) will, so, if you want both, a simple workaround would be to just include both patterns in your table of combinations.
If you actually have many more columns than shown in your example, and you want to match patterns that occur in any set of consecutive columns, then your really should pack your columns into a string and use a LIKE or REGEXP query. For example, if you concatenate all your data columns into a comma-separated string in a column named data, you could search it like this:
INSERT INTO combinations (pattern) VALUES
('1,2'), ('4,10'), ('1,2,3'), ('3,10,4'), ('7,8,9');
SELECT c.pattern, COUNT(t.id) AS num
FROM combinations AS c
LEFT JOIN my_table AS t
ON CONCAT(',', t.data, ',') LIKE CONCAT('%,', c.pattern, ',%')
GROUP BY c.id;
(demo on SQLize)
You could make this query somewhat faster by making the prefixes and suffixes added with CONCAT() part of the actual data in the tables, but this is still going to be a fairly inefficient query if you have a lot of data to search, because it cannot make use of indexes. If you need to do this kind of substring searching on large datasets efficiently, you may want to use something better suited for than specific purpose than MySQL.
You only have three columns in the table, so you are looking for combinations of 1, 2, and 3 elements.
For simplicity, I'll start with the following table:
select index, n1 as n from t union all
select index, n2 from t union all
select index, n3 from t union all
select distinct index, -1 from t union all
select distinct index, -2 from t
Let's call this "values". Now, we want to get all triples from this table for a given index. In this case, -1 and -2 represent NULL.
select (case when v1.n < 0 then NULL else v1.n end) as n1,
(case when v2.n < 0 then NULL else v2.n end) as n2,
(case when v3.n < 0 then NULL else v3.n end) as n3,
count(*) as NumOccurrences
from values v1 join
values v2
on v1.n < v2.n and v1.index = v2.index join
values v3
on v2.n < v3.n and v2.index = v3.index
This is using the join mechanism to generate the combinations.
This method finds all combinations regardless of ordering (so 1, 2, 3 is the same as 2, 3, 1). Also, this ignores duplicates, so it cannot find (1, 2, 2) if 2 is repeated twice.
SELECT
CONCAT(CAST(n1 AS VARCHAR(10)),'|',CAST(n2 AS VARCHAR(10)),'|',CAST(n3 AS VARCHAR(10))) AS Combination,
COUNT(CONCAT(CAST(n1 AS VARCHAR(10)),'|',CAST(n2 AS VARCHAR(10)),'|',CAST(n3 AS VARCHAR(10)))) AS Occurrences
FROM
MyTable
GROUP BY
CONCAT(CAST(n1 AS VARCHAR(10)),'|',CAST(n2 AS VARCHAR(10)),'|',CAST(n3 AS VARCHAR(10)))
This creates a single column that represents the combination of the values within the 3 columns by concatenating the values. It will count the occurrences of each.