I have a MySQL table that looks like this:
id layer l_to blank
1 1 10 xyz
0 0 5.5 xyz
I want to get the highest number of column-variable "l_to" that shares column-variable "blank".
I have tried the following SQL-query:
SELECT MAX(l_to), COUNT(layer),l_from FROM layers WHERE blank='xyz'
This works fine, if "l_to" of layer 1 is below 10. If it is ten, the query returns "l_to" from layer 0 (5.5).
Any Idea for why this is, and how can I retrieve the MAX?
#EDIT: Changing Datatype of "l_to" from VARCHAR to DECIMAL (5,1) got me the desired result. Thanks for the answers!
The datatype is not a number for field l_to so 5 is greater than 1 for a string. Probably a varchar. Change field l_to to a Decimal [1].
Only consider casting if you do not have control over the table structure as best practice is the data type reflects the data use in the world. This protects the data integrity of the database, provides helpful functions related to the datatype and ensures intuitive outcomes, like Max function. Casting as a work around for this query will only lead to downstream issues; refactor the structure now if you can.
Reference
Decimal data type suggested in comments by #Akina. Originally suggested float, but Decimal appears to reflect the Use Case better than float, given the limited examples shown.
Cast l_to from string to decimal
SELECT MAX(cast(l_to as DECIMAL(10,2)), COUNT(layer) from FROM layers WHERE blank='xyz'
Use a LIMIT query, and also cast the l_to column to decimal:
SELECT *
FROM layers
WHERE blank = 'xyz'
ORDER BY CAST(l_to AS DECIMAL(12.4)) DESC
LIMIT 1;
I am having a hard time figuring this one out so I came here for help.
I have a table x_25_operators which has a field called mask.
Masks are numbers with length between 7-11 digits. What I am trying to achieve here is to find the best match for my query at this particular table.
Given the scenario:
x_25_operators
| some_other_data | mask
. 486737
. 616724
. 915776
I have a number: 48915776148 (this number is fixed-length, always 11 digits)
I am looking for a query which will return a row containing mask 915776 (or all rows fitting to this searched number as filtering best-matching-one out should be a piece of cake).
I was thinking of using LIKE as the filter but such query:
SELECT * FROM x_25_operators WHERE mask LIKE '48915776148'
returns an empty query (which should be kind of obvious).
I am using a mySQL database.
Any ideas how to tackle such problem? I am open to any suggestions.
You can use LOCATE()
SELECT * FROM x_25_operators WHERE LOCATE(mask , "48915776148")
Here is some more info: https://www.w3resource.com/mysql/string-functions/mysql-locate-function.php
Firstly I want this to be purely done with MySQL query.
I have a series of Invoice numbers
invoice_number
INV001
INV002
INV003
INV004
INV005
001
002
003
006
007
009
010
INVOICE333
INVOICE334
INVOICE335
INVOICE337
INVOICE338
INVOICE339
001INV
002INV
005INV
009INV
I want to output something like this
from_invoice_no to_invoice_no total_invoices
INV001 INV005 5
001 010 7
INVOICE333 INVOICE339 6
001INV 009INV 4
The invoice number pattern cannot be fixed. They can change in future
Please help me to achieve this.
Thanks in advance.
I will first show a general idea how to solve this problem and provide some code which will be ugly, but easily understandable. Then I'll explain what the issues are and how to remedy them.
STEP 1: Deriving the grouping criterion
For the first step, I assume you have the right (privilege) to create an additional column in your table. Let us name it invoice_text. Now, the general idea is to remove all digits from the invoice number so that only the "text pattern" remains. Then we can group by the text pattern.
Assuming that you have already created the column mentioned above, you could do the following:
UPDATE Invoices SET invoice_text = REPLACE(invoice_number, '0', '');
UPDATE Invoices SET invoice_text = REPLACE(invoice_text, '1', '');
UPDATE Invoices SET invoice_text = REPLACE(invoice_text, '2', '');
...
UPDATE Invoices SET invoice_text = REPLACE(invoice_text, '9', '');
After having done that, you will have the pure text pattern without digits in invoice_text and can use that for grouping:
SELECT COUNT(invoice_number) AS total_invoices FROM Invoices
GROUP BY invoice_text
This is nice, but it is not yet what you wanted. It does not show the first and last invoice number for each group.
STEP 2: Deriving the first and last invoice for each group
For this step, create one more column in your table. Let us name it invoice_digits. As the name implies, it is meant to take only the pure invoice number without the "pattern text".
Assuming you have that column, you could do the following:
UPDATE Invoices SET invoice_digits = REPLACE(invoice_number, 'A', '');
UPDATE Invoices SET invoice_digits = REPLACE(invoice_digits, 'B', '');
UPDATE Invoices SET invoice_digits = REPLACE(invoice_digits, 'C', '');
...
UPDATE Invoices SET invoice_digits = REPLACE(invoice_digits, 'Z', '');
Now, you can use that column to get the minimum and maximum invoice number (without "pattern text"):
SELECT
MIN(invoice_digits) AS from_invoice_no,
MAX(invoice_digits) AS to_invoice_no,
COUNT(invoice_number) AS total_invoices
FROM Invoices
GROUP BY invoice_text
Problems and how to solve them
1) According to your question, you want to get the minimum and maximum full invoice number text. The solution above will show only the minimum and maximum invoice number text without the text parts, i.e. only the digits.
We could remedy this by doing a further JOIN, but since I can very well imagine that you won't insist on this :-), and since it won't make the general idea more clear, I am leaving this to you. If you are interested, let us know.
2) It might be difficult to decide what a digit (i.e. what the actual invoice number) is. For example, if you have invoice numbers like INV001, INV002, this will be no problem, but what if you have INV001/001, INV001/002, INV002/003 and so on? In this example, my code would would yield 001001, 001002, 002003 as actual invoice numbers and use that to decide what the minimum and maximum numbers are.
This might not be what you want to do in that case. The only way around this is that you thoroughly think about what you should consider a digit and what not, and to adapt my code accordingly.
3) My code currently uses string comparisons to get the minimum and maximum invoice numbers. This may yield other results than comparing the values as numbers. If you are wondering what that means: Compare '19' to '9' as string, and compare 19 to 9 as number.
If this is a problem, then use MySQL's CAST to convert the text to a number before feeding it to MAX or MIN. But please be aware that this has its own caveats:
If you have very long invoice numbers with so many digits that they don't fit into MySQL's numeric data types, this method will fail. It will also fail if you have defined a character like / to be digits (due to the issues described in 2)) since MySQL can't convert this into a number.
Instead of converting to numbers, you can also pad the values in invoice_digits with leading zeroes, for example using MySQL's LPAD function. This will avoid the problems described above and sort the numbers as expected, even if they include non-digits like /, but you will have to know the maximum length of the digit string in advance.
4) The code is ugly! Do you really have to remove all possible characters from A to Z one by one by doing UPDATE statements to get the digit string?
Actually, it is even worse. I just have assumed that you only have the "text characters" A to Z in your invoices. But there could be any character Unicode defines: Russian or Chinese ones, special characters, in other words: thousands of different characters.
Unfortunately, AFAIK, MySQL still does not provide a REGEX-REPLACE function. I don't see any chance to get this problem solved unless you extend MySQL with an appropriate UDF (user defined function). There are some cool guys out there who have recognized the problem and have added such functions to MySQL. Since recommending libraries seems to be discouraged on SO, just google for "mysql regex replace".
When having extended MySQL that way, you can replace the ugly bunch of UPDATE statements which remove the digits / the text from the invoice number by a single one (using a REGEX, you can replace all digits or all non-digits at once).
For the sake of completeness, you could avoid the many UPDATE statements by doing UPDATE ... SET ... = REPLACE(REPLACE(REPLACE(...))) and thus applying all updates with one statement. But this is even more ugly and error prone, so if you are serious about your problem, you'll really have to extend MySQL by a REGEX-REPLACE.
5) The solution will only work if you have the privilege to create new columns in the table.
This is true for the solution as-is. But I have chosen to go that way solely because it makes the general idea clear and understandable. Instead of adding columns to your original table, you could also create a new table where you store the pure text / digits (this table might be a temporary one).
Furthermore, since MySQL supports grouping by computed values, you don't need additional columns / tables at all. You should decide by yourself what is the best way to go.
Is it possible to find the min value of a column of floating numbers using a mysql function? Suppose I have the following table:
id | value a | 24.88 a | 119.99
If I try:
SELECT MIN(value) FROM [table name] GROUP BY id;
mysql returns:
119.99
After testing this with different floating numbers I believe that this is the case because mysql takes the first character in each of the strings "1" and "2" and then selects a min based on which character is smaller.
I've read through this forum and others trying to find an answer but it seems nobody has raised this problem.
I should mention I've also tried CEIL(value) but that function also seems to have some bugs and I'd prefer to keep the number a floating number and not an integer.
Thanks everyone.
It looks like the column is being stored as a character-based data type. You can solve this in one of two ways:
Change the column type to a numeric type
change the query to add CAST around the value: MIN(CAST(value AS DECIMAL))
The column change might look like this:
ALTER TABLE my_table MODIFY COLUMN value double;
And, as far as I know, MySQL will attempt to convert the data for you. See the note here, which states it "tries".
I have an InnoDB database table of 12 character codes which often need to be entered by a user.
Occasionally, a user will enter the code incorrectly (for example typing a lower case L instead of a 1 etc).
I'm trying to write a query that will find similar codes to the one they have entered but using LIKE '%code%' gives me way too many results, many of which contain only one matching character.
Is there a way to perform a more detailed check?
Edit - Case sensitive not required.
Any advice appreciated.
Thanks.
Have a look at soundex. Commonly misspelled strings have the same soundex code, so you can query for:
where soundex(Code) like soundex(UserInput)
use without wildcard % for that
SELECT `code` FROM table where code LIKE 'user_input'
thi wil also check the space
SELECT 'a' = 'a ', return 1 whereas SELCET 'a' LIKE 'a ' return 0
reference