In my database, a table contains two columns each containing an 8 digit ASCII code, usually it's just alphanumeric. For example, a row might contain A123B45C in col1 and PQ2R4680 in col2.
I need to have a query/view that outputs a 4 character string calculated as the 2nd+3rd chars of these, concatenated. So in this example the extra column value would be 12Q2.
This is a cut-down version of the SQL I'd like to use, although it won't work as written because of zero stripping / conversion:
select
*,
(substr(col1, 2, 2) || substr(col2, 2, 2)) AS mode
from (nested SQL source query)
where (conditions)
This fails because if a row contains A00B23B4 in col1 and P32R4680 in col2, it will evaluate as 0032 and the query output will contain numeric 32 not 0032. (It's worse if col1 contains P1-2345 or "1.23456" or something like that)
Other questions on preventing zero stripping and string to integer conversion in Sqlite, all relate to data in tables where you can define a column text affinity, or static (quotable) data. In this case I can't do these things. I also can only create queries, not tables, so I can't write to a temp table.
What is the best way to ensure I get a 4 character output in all cases?
I believe you issue is not with substr stripping characters as this works as expected e.g. :-
Then running query SELECT substr(col1,2,2) || substr(col2,2,2) as mode FROM stripping
results in (as expected):-
Rather, your issue is likely how you subsequently utilise mode in which case you may need to use a CAST expression CAST expressions
For example the following does what is possibly happening :-
`SELECT substr(col1,2,2) || substr(col2,2,2) as mode, CAST(substr(col1,2,2) || substr(col2,2,2) AS INTEGER) AS oops FROM stripping`
resulting in :-
Related
I have a column C of type REAL in table F in SQLite. I want to join this everywhere where in another table the negative value of F exists (along with some other fields).
However -C or 0-C etc.. all return the rounded value of C e.g. when C contains "123,456" then -C returns "-123".
Should I cast this via a string first or is the syntax differently?
Looks like the , in 123,456 is meant to be a decimal separator but SQLite treats the whole thing as a string (i.e. '123,456' rather than 123.456). Keep in mind that SQLite's type system is a little different than SQL's as values have types but columns don't:
[...] In SQLite, the datatype of a value is associated with the value itself, not with its container. [...]
So you can quietly put a string (that looks like a real number in some locales) into a real column and nothing bad happens until later.
You could fix the import process to interpret the decimal separator as desired before the data gets into SQLite or you could use replace to fix them up as needed:
sqlite> select -'123,45';
-123
sqlite> select -replace('123,45', ',', '.');
-123.45
With NVARCHAR data type, I store my local language text in a column. I face a problem how to query that value from the database.
ዜናገብርኤልስ is stored value.
I wrote SQL like this
select DivisionName
from t_Et_Divisions
where DivisionName = 'ዜናገብርኤልስ'
select unicode (DivisionName)
from t_Et_Divisions
where DivisionName = 'ዜናገብርኤልስ'
The above didn't work. Does anyone have any ideas how to fix it?
Thanks!
You need to prefix your Unicode string literals with a N:
select DivisionName
from t_Et_Divisions
where DivisionName = N'ዜናገብርኤልስ'
This N prefix tells SQL Server to treat this string literal as a Unicode string and not convert it to a non-Unicode string (as it will if you omit the N prefix).
Update:
I still fail to understand what is not working according to you....
I tried setting up a table with an NVARCHAR column, and if I select, I get back that one, exact row match - as expected:
DECLARE #test TABLE (DivisionName NVARCHAR(100))
INSERT INTO #test (DivisionName)
VALUES (N'ዜናገብርኤልስ'), (N'ዜናገብርኤልስ,ኔትዎርክ,ከስተመር ስርቪስ'), (N'ኔትዎርክ,ከስተመር ስርቪስ')
SELECT *
FROM #test
WHERE DivisionName = N'ዜናገብርኤልስ'
This returns exactly one row - what else are you seeing, or what else are you expecting??
Update #2:
Ah - I see - the columns contains multiple, comma-separated values - which is a horrible design mistake to begin with..... (violates first normal form of database design - don't do it!!)
And then you want to select all rows that contain that search term - but only display the search term itself, not the whole DivisionName column? Seems rather pointless..... try this:
select N'ዜናገብርኤልስ'
from t_Et_Divisions
where DivisionName LIKE N'%ዜናገብርኤልስ%'
The LIKE searches for rows that contain that value, and since you already know what you want to display, just put that value into the SELECT list ....
I am trying to convert from a string representing hex data to the textual encoding (ASCII, UTF-8, etc.) of the hex data using purely SQLite language. Essentially I want the functionality of the X'[hex]' syntax, but applied to a programmatically derived hex string.
I want, for example, select X(hex_data_string) from ..., which is not legal SQLite syntax.
Obviously in the above snippet, I would not necessarily be able to output the data if it was not in a valid textual encoding. That is, if hex_data_string contains control chars, etc., the X() should fail in some way. If this is possible, there would have to be a default character encoding or the desired character encoding would have to be specified somehow.
I am not asking about how to retrieve the hex data string value from the SQLite database and then use C or some other facility to convert it. I am trying to perform this conversion in pure SQLite because I have queries that I check which return a text representation of hex characters representing binary data. Most of the binary data is ASCII, so I want to be able to quickly view the content of the binary data in my query output when applicable.
Intuitively, I figured this could be accomplished by casting the hex data string to a blob and using hex() but that still returns the hex data string.
Any ideas?
Possible duplicates:
SQLite X'...' notation with column data
sqlite char, ascii function
This is quite old but I was looking for the same thing so I thought I'd post:
It seems you can just cast hex data as a varchar to convert it to ascii.
ie:
select cast(data as varchar) from some_table will return a string representation of a binary field (data).
This is not possible in pure SQLite.
As an embedded database, SQLite is designed to provide only pure database functions, and leave the program logic to the the application.
You are supposed to retrieve the hex data string value from the SQLite database and then use C or some other facility to convert it.
If you control the program you're running the queries in, you could install a user-defined function that does this conversion.
This will not be fully useful since it can't really be used inline, but I have done this in the past when I just wanted to convert one row of data and not create/find another utility.
WITH RECURSIVE test(c,cur) as (
select '','686F77647921'
UNION ALL
select c || char((case substr(cur,1,1) when 'A' then 10 when 'B' then 11 when 'C' then 12 when 'D' then 13 when 'E' then 14 when 'F' then 15 else substr(cur,1,1) end)*16
+ (case substr(cur,2,1) when 'A' then 10 when 'B' then 11 when 'C' then 12 when 'D' then 13 when 'E' then 14 when 'F' then 15 else substr(cur,2,1) end)),
substr(cur,3)
from test where length(cur)>0
)
select * from test
I would like to query an SQLite table that contains directory paths to find all the paths under some hierarchy. Here's an example of the contents of the column:
/alpha/papa/
/alpha/papa/tango/
/alpha/quebec/
/bravo/papa/
/bravo/papa/uniform/
/charlie/quebec/tango/
If I search for everything under /bravo/papa/, I would like to get:
/bravo/papa/
/bravo/papa/uniform/
I am currently trying to do this like so (see below for the long story of why I can't use more simple methods):
SELECT * FROM Files WHERE Path >= '/bravo/papa/' AND Path < '/bravo/papa0';
This works. It looks a bit weird, but it works for this example. '0' is the unicode code point 1 greater than '/'. When ordered lexicographically, all the paths starting with '/bravo/papa/' compare greater than it and less than 'bravo/papa0'. However, in my tests, I find that this breaks down when we try this:
SELECT * FROM Files WHERE Path >= '/' AND Path < '0';
This returns no results, but it should return every row. As far as I can tell, the problem is that SQLite is treating '0' as a number, not a string. If I use '0Z' instead of '0', for example, I do get results, but I introduce a risk of getting false positives. (For example, if there actually was an entry '0'.)
The simple version of my question is: is there some way to get SQLite to treat '0' in such a query as the length-1 string containing the unicode character '0' (which should sort strings such as '!', '*' and '/', but before '1', '=' and 'A') instead of the integer 0 (which SQLite sorts before all strings)?
I think in this case I can actually get away with special-casing a search for everything under '/', since all my entries will always start with '/', but I'd really like to know how to avoid this sort of thing in general, as it's unpleasantly surprising in all the same ways as Javascript's "==" operator.
First approach
A more natural approach would be to use the LIKE or GLOB operator. For example:
SELECT * FROM Files WHERE Path LIKE #prefix || '%';
But I want to support all valid path characters, so I would need to use ESCAPE for the '_' and '%' symbols. Apparently this prevents SQLite from using an index on Path. (See http://www.sqlite.org/optoverview.html#like_opt ) I really want to be able to benefit from an index here, and it sounds like that's impossible using either LIKE or GLOB unless I can guarantee that none of their special characters will occur in the directory name, and POSIX allows anything other than NUL and '/', even GLOB's '*' and '?' characters.
I'm providing this for context. I'm interested in other approaches to solve the underlying problem, but I'd prefer to accept an answer that directly addresses the ambiguity of strings-that-look-like-numbers in SQLite.
Similar questions
How do I prevent sqlite from evaluating a string as a math expression?
In that question, the values weren't quoted. I get these results even when the values are quoted or passed in as parameters.
EDIT - See my answer below. The column was created with the invalid type "STRING", which SQLite treated as NUMERIC.
* Groan *. The column had NUMERIC affinity because it had accidentally been specified as "STRING" instead of "TEXT". Since SQLite didn't recognize the type name, it made it NUMERIC, and because SQLite doesn't enforce column types, everything else worked as expected, except that any time a number-like string is inserted into that column it is converted into a numeric type.
I am trying to write a custom report in Spiceworks, which uses SQLite queries. This report will fetch me hard drive serial numbers that are unfortunately stored in a few different ways depending on what version of Windows and WMI were on the machine.
Three common examples (which are enough to get to the actual question) are as follows:
Actual serial number: 5VG95AZF
Hexadecimal string with leading spaces: 2020202057202d44585730354341543934383433
Hexadecimal string with leading zeroes: 3030303030303030313131343330423137454342
The two hex strings are further complicated in that even after they are converted to ASCII representation, each pair of numbers are actually backwards. Here is an example:
3030303030303030313131343330423137454342 evaluates to 00000000111430B17ECB
However, the actual serial number on that hard drive is 1141031BE7BC, without leading zeroes and with the bytes swapped around. According to other questions and answers I have read on this site, this has to do with the "endianness" of the data.
My temporary query so far looks something like this (shortened to only the pertinent section):
SELECT pd.model as HDModel,
CASE
WHEN pd.serial like "30303030%" THEN
cast(('X''' || pd.serial || '''') as TEXT)
WHEN pd.serial like "202020%" THEN
LTRIM(X'2020202057202d44585730354341543934383433')
ELSE
pd.serial
END as HDSerial
The result of that query is something like this:
HDModel HDSerial
----------------- -------------------------------------------
Normal Serial 5VG95AZF
202020% test case W -DXW05CAT94843
303030% test case X'3030303030303030313131343330423137454342'
This shows that the X'....' notation style does convert into the correct (but backwards) result of W -DXW05CAT94843 when given a fully literal number (the 202020% line). However, I need to find a way to do the same thing to the actual data in the column, pd.serial, and I can't find a way.
My initial thought was that if I could build a string representation of the X'...' notation, then perhaps cast() would evaluate it. But as you can see, that just ends up spitting out X'3030303030303030313131343330423137454342' instead of the expected 00000000111430B17ECB. This means the concatenation is working correctly, but I can't find a way to evaluate it as hex the same was as in the manual test case.
I have been googling all morning to see if there is just some syntax I am missing, but the closest I have come is this concatenation using the || operator.
EDIT: Ultimately I just want to be able to have a simple case statement in my query like this:
SELECT pd.model as HDModel,
CASE
WHEN pd.serial like "30303030%" THEN
LTRIM(X'pd.serial')
WHEN pd.serial like "202020%" THEN
LTRIM(X'pd.serial')
ELSE
pd.serial
END as HDSerial
But because pd.serial gets wrapped in single quotes, it is taken as a literal string instead of taken as the data contained in that column. My hope was/is that there is just a character or operator I need to specify, like X'$pd.serial' or something.
END EDIT
If I can get past this first hurdle, my next task will be to try and remove the leading zeroes (the way LTRIM eats the leading spaces) and reverse the bytes, but to be honest, I would be content even if that part isn't possible because it wouldn't be hard to post-process this report in Excel to do that.
If anyone can point me in the right direction I would greatly appreciate it! It would obviously be much easier if I was using PHP or something else to do this processing, but because I am trying to have it be an embedded report in Spiceworks, I have to do this all in a single SQLite query.
X'...' is the binary representation in sqlite. If the values are string, you can just use them as such.
This should be a start:
sqlite> select X'3030303030303030313131343330423137454342';
00000000111430B17ECB
sqlite> select ltrim(X'3030303030303030313131343330423137454342','0');
111430B17ECB
I hope this puts you on the right path.