I have a mysql database that contains a range of postcode district ranges.
I am trying to find the row that matches the given district, in this example 'SY18'.
I have mysql query below, but it returns both the values in the table because the fields are alphanumeric.
SELECT rate FROM table WHERE district_from <= 'SY18' AND district_to >= 'SY18'
Table example
id district_from district_to rate
1 SY1 SY9 10
2 SY16 SY22 20
3 AL1 AL99 37
4 B1 B99 37
5 BB1 BB99 37
6 CB1 CB99 40
How do I return only correct results?
You can use SUBSTR to skip first characters of the string and then +0 to consider the value as a number. Example:
SELECT v
FROM
(SELECT 'SY1' v UNION SELECT 'SY16') t
WHERE SUBSTR(t.v, 3)+0 > 10
;
CREATE FUNCTION normalize_district (district VARCHAR(4))
RETURNS VARCHAR(4) DETERMINISTIC
RETURN CONCAT( TRIM(TRAILING CASE WHEN 0 + RIGHT(district, 2) > 0
THEN RIGHT(district, 2)
ELSE RIGHT(district, 1) END FROM district),
LPAD(CASE WHEN 0 + RIGHT(district, 2) > 0
THEN 0 + RIGHT(district, 2)
ELSE 0 + RIGHT(district, 1) END, 2, '0') );
and then
SELECT *
FROM district_to_test
LEFT JOIN rate ON normalize_district(district_to_test.district)
BETWEEN normalize_district(district_from)
AND normalize_district(district_to);
fiddle
0 + RIGHT(district, 2) > 0 in the function thecks does the last 2 symbols in district are digits.
If true then 2-digit number wil be extracted by RIGHT(), and the whole expression value will be above zero (you claim that there is no values like 'AA0' or 'AA00').
If false, and only one digit is present, then RIGHT() will give a substring which is started from a letter, and the value will be zero.
Based on this I divide the whole value to a prefix and numeric postfix, and add a zero to the numeric part making it 2-digit unconditionally. Such value can be used for direct string comparing by BETWEEN operator.
The goal of a function is to convert the value to 'AA00' format. For this purposes we must divide the whole value to textual and numeric parts and normalize (zero-pad) the latter one.
You may use any other dividing method. For example, you may check does the value contains two digits using LIKE '%\\d\\d'. Or backward, you may determine does the value contains two letters using LIKE '\\D\\D%'... these methods have relatively equal difficulty.
Related
I am dealing with a table of decimal values that represent binary numbers. My goal is to count the number of times Bit(0), Bit(1),... Bit(n) are high.
For example, if a table entry is 5 this converts to '101' which can be done using the BIN() function.
What I would like to do is increment a variable 'bit0Count' and 'bit2Count'
I have looked into the BIT_COUNT() function however this would only return 2 for the above example.
Any insight would be greatly appreciated.
SELECT SUM(n & (1<<2) > 0) AS bit2Count FROM ...
The & operator is a bitwise AND.
1<<2 is a number with only 1 bit set, left-shifted by two places, so it is binary 100. Using bitwise AND against you column n is either binary 100 or binary 000.
Testing that with > 0 returns either 1 or 0, since in MySQL, boolean results are literally the integers 1 for true and 0 for false (note this is not standard in other implementations of SQL).
Then you can SUM() these 1's and 0's to get a count of the occurrences where the bit was set.
To tell if bit N is set, use 1 << N to create a mask for that bit and then use bitwise AND to test it. So (column & (1 << N)) != 0 will be 1 if bit N is set, 0 if it's not set.
To total these across rows, use the SUM() aggregation function.
If you need to do this frequently, you could define a stored function:
CREATE FUNCTION bit_set(UNSIGNED INT val, TINYINT which) DETERMINISTIC
RETURN (val & (1 << which)) != 0;
I have a column like below.
Value
_____
48
48
39
96
50
I want to divide this with 48.
From the above 5 values, row 1,2,4 can be divided, but 3,5 not. I have to do this with SQL.
EG:
select count(*) from tbl where value/42
Result: 2
You are asking for the remainder when an integer is divided by 48. That has a specific name in mathematics, the modulo operation. This is actually a very interesting (to some people) part of number theory and group theory.
Most databases support the modulo operator or function via %. So the idea is:
select value
from t
where value % 48 = 0;
This might be:
where value mod 48 = 0
where mod(value, 48) = 0
depending on the database.
Another method is:
where floor(val / 48) * 48 = val
You can do that with a simple where clause
SELECT value FROM table WHERE value%48 = 0
The modulus operator returns the remainder for the division of the operands which in fact means we are checking if the numbers are divisible (remainder is zero when numbers are divisible)
So, if you are trying to count what’s not divisible then simple use below query
SELECT count(value) FROM table WHERE value%48 != 0
You can use modulus(%) to find the result. Check below query it will help you.
declare #tbl table (val int)
insert #tbl values(48),(48),(39),(96),(50)
select * from #tbl where val % 48 =0
Output
val
48
48
96
Can anyone lend me a hand as to what I should append to my ORDER BY statement to sort these values naturally:
1
10
2
22
20405-109
20405-101
20404-100
X
Z
D
Ideally I'd like something along the lines of:
1
2
10
22
20404-100
20405-101
20405-109
D
X
Z
I'm currently using:
ORDER BY t.property, l.unit_number
where the values are l.unit_number
I've tried doing l.unit_number * 1 and l.unit_number + 0 but they haven't worked.
Should I be doing sort of ORDER conditional, such as Case When IsNumeric(l.unit_number)?
Thank you.
This will do it:
SELECT value
FROM Table1
ORDER BY value REGEXP '^[A-Za-z]+$'
,CAST(value as SIGNED INTEGER)
,CAST(REPLACE(value,'-','')AS SIGNED INTEGER)
,value
The 4 levels of the ORDER BY:
REGEXP assigns any alpha line a 1 and non-alphas a 0
SIGNED INT Sorts all of the numbers by the portion preceding the dash.
SIGNED INT after removing the dash sorts any of the items with the same value before the dash by the portion after the dash. Potentially could replace number 2, but wouldn't want to treat 90-1 the same as 9-01 should the case arise.
Sorts the letters alphabetically.
Demo: SQL Fiddle
I have two tables "A" and "B". Table "A" has two columns "Body" and "Number." The column "Number" is empty, the purpose is to populate it.
Table A: Body / Number
ABABCDEF /
IJKLMNOP /
QRSTUVWKYZ /
Table "B" only has one column:
Table B: Values
AB
CD
QR
Here is what I am looking for as a result:
ABABCDEF / 3
IJKLMNOP / 0
QRSTUVWKYZ / 1
In other words, I want to create a query that looks up, for each string in the "Body" column, how many times the substrings in the "Values" column appear.
How would you advise me to do that?
Here's the finished query; explanation will follow:
SELECT
Body,
SUM(
CASE WHEN Value IS NULL THEN 0
ELSE (LENGTH(Body) - LENGTH(REPLACE(Body, Value, ''))) / LENGTH(Value)
END
) AS Val
FROM (
SELECT TableA.Body, TableB.Value
FROM TableA
LEFT JOIN TableB ON INSTR(TableA.Body, TableB.Value) > 0
) CharMatch
GROUP BY Body
There's a SQL Fiddle here.
Now for the explanation...
The inner query matches TableA strings with TableB substrings:
SELECT TableA.Body, TableB.Value
FROM TableA
LEFT JOIN TableB ON INSTR(TableA.Body, TableB.Value) > 0
Its results are:
BODY VALUE
-------------------- -----
ABABCDEF AB
ABABCDEF CD
IJKLMNOP
QRSTUVWKYZ QR
If you just count these you'll only get a value of 2 for the ABABCDEF string because it just looks for the existence of the substrings and doesn't take into consideration that AB occurs twice.
MySQL doesn't appear to have an OCCURS type function, so to count the occurrences I used the workaround of comparing the length of the string to its length with the target string removed, divided by the length of the target string. Here's an explanation:
REPLACE('ABABCDEF', 'AB', '') ==> 'CDEF'
LENGTH('ABABCDEF') ==> 8
LENGTH('CDEF') ==> 4
So the length of the string with all AB occurrences removed is 8 - 4, or 4. Divide the 4 by 2 (LENGTH('AB')) to get the number of AB occurrences: 2
String IJKLMNOP will mess this up. It doesn't have any of the target values so there's a divide by zero risk. The CASE inside the SUM protects against this.
You want an update query:
update A
set cnt = (select sum((length(a.body) - length(replace(a.body, b.value, '')) / length(b.value))
from b
)
This uses a little trick for counting the number of occurrence of b.value in a given string. It replaces each occurrence with an empty string and counts the difference in length of the strings. This is divided by the length of the string being replaced.
If you just wanted the number of matches (so the first value would be "2" instead of "3"):
update A
set cnt = (select count(*)
from b
where a.body like concat('%', b.value, '%')
)
I'm having trouble with this SQL:
$sql = mysql_query("SELECT $menucompare ,
(COUNT($menucompare ) * 100 / (SELECT COUNT( $menucompare )
FROM data WHERE $ww = $button )) AS percentday FROM data WHERE $ww >0 ");
$menucompare is table fields names what ever field is selected and contains data bellow
$button is the week number selected (lets say week '6')
$ww table field name with row who have the number of week '6'
For example, I have data in $menucompare like that:
123456bool
521478bool
122555heel
147788itoo
and I want to select those, who have same word in the last of the data and make percentage.
The output should be like that:
bool -- 50% (2 entries)
heel -- 25% (1 entry)
itoo -- 25% (1 entry)
Any clearness to my SQL will be very appreciated.
I didn't find anything like that around.
Well, keeping data in such format probably not the best way, if possible, split the field into 2 separate ones.
First, you need to extract the string part from the end of the field.
if the length of the string / numeric parts is fixed, then it's quite easy;
if not, you should use regular expressions which, unfortunately, are not there by default with MySQL. There's a solution, check this question: How to do a regular expression replace in MySQL?
I'll assume, that numeric part is fixed:
SELECT s.str, CAST(count(s.str) AS decimal) / t.cnt * 100 AS pct
FROM (SELECT substr(entry, 7) AS str FROM data) AS s
JOIN (SELECT count(*) AS cnt FROM data) AS t ON 1=1
GROUP BY s.str, t.cnt;
If you'll have regexp_replace function, then substr(entry, 7) should be replaced to regexp_replace(entry, '^[0-9]*', '') to achieve the required result.
Variant with substr can be tested here.
When sorting out problems like this, I would do it in two steps:
Sort out the SQL independently of the presentation language (PHP?).
Sort out the parameterization of the query and the presentation of the results after you know you've got the correct query.
Since this question is tagged 'SQL', I'm only going to address the first question.
The first step is to unclutter the query:
SELECT menucompare,
(COUNT(menucompare) * 100 / (SELECT COUNT(menucompare) FROM data WHERE ww = 6))
AS percentday
FROM data
WHERE ww > 0;
This removes the $ signs from most of the variable bits, and substitutes 6 for the button value. That makes it a bit easier to understand.
Your desired output seems to need the last four characters of the string held in menucompare for grouping and counting purposes.
The data to be aggregated would be selected by:
SELECT SUBSTR(MenuCompare, -4) AS Last4
FROM Data
WHERE ww = 6
The divisor in the percentage is the count of such rows, but the sub-stringing isn't necessary to count them, so we can write:
SELECT COUNT(*) FROM Data WHERE ww = 6
This is exactly what you have anyway.
The divdend in the percentage will be the group count of each substring.
SELECT Last4, COUNT(Last4) * 100.0 / (SELECT COUNT(*) FROM Data WHERE ww = 6)
FROM (SELECT SUBSTR(MenuCompare, -4) AS Last4
FROM Data
WHERE ww = 6
) AS Week6
GROUP BY Last4
ORDER BY Last4;
When you've demonstrated that this works, you can re-parameterize the query and deal with the presentation of the results.