I have a table with a numeric(6,4) column (x.xxxx)
In the select statement, I have to do math on this column which results in the value being typed as a REAL. I need to display the results using numeric(6,4) though and can't seem to see how to do this.
I tried "cast(column as numeric(6,4))" which works in other databases, but the displayed value is still REAL format with more than 4 digits to the right of the decimal. I need to get it back to the "x.xxxx" format from REAL.
Related
I am a somewhat newbie to SQLite (and KMyMoney). KMyMoney (an open source personal finance manager) allows one-click exporting data into an SQLite database.
On browsing the SQLite database output, the dollar amount data is stored in a table called kmmSplits as several text fields in a strange format based on “value” and “valueFormatted” (see screen shot below). The “value” field is apparently written as a division equation (in a text format) which apparently yields the “valueFormatted” field (again in text format). The “valueFormatted is the correct number amount but the problem is that parenthesis are used to indicate a negative number instead of a simple minus in front of the value. This is apparently an accounting number format, but I don’t know how to parse this into a float value for running calculated SQL queries, etc. The positive values (without parenthesis) are no problem to convert to FLOATS.
I’ve tried using the CAST to FLOAT function but this does not do the division math, nor does it convert parenthesis into negative values (see screen shot).
The basic question is: how to parse a text value containing parenthesis in the “valueFormatted field (accounting money format) into a common number format OR, alternatively, how to convert a division equation in the “value” field to an actual calculation.
Use a CASE expression to check if valueFormatted is a numeric value inside parentheses and if it is multiply -1 with the substring starting from the 2nd char (the closing parenthesis will be discarded by SQLite during this implicit type casting):
SELECT *,
CASE
WHEN valueFormatted LIKE '(%)' THEN (-1) * SUBSTR(valueFormatted, 2)
ELSE valueFormatted
END AS value
FROM kmmSQLite;
Or, replace '(' with ''-'' and add 0 to covert the result to a number:
SELECT *,
REPLACE(valueFormatted, '(', '-') + 0 AS value
FROM kmmSQLite;
I want to limit numeric column type to 10 symbols before decimal separator and 4 symbols after decimal separator. I executed the following command:
ALTER TABLE scustdisc ADD COLUMN spec_price numeric(10,4)
The command executed without errors but when I try to insert value in spec_price 10.123456 I am able to do it. It should give error and the value not to be inserted. Am I wrong in my alter command?
SQLite has a dynamic type system and the column types have a limited impact, but can be virtually any name. They are resolved to one of TEXT, NUMERIC, INTEGER, REAL or BLOB.
numeric(0,0) - numeric(99999999,99999999) and more resolve to NUMERIC.
As such 10,4 4,10 etc means nothing and makes no difference to SQLite.
With one exception bar constraints a column may hold any type of value. The column type only comes into play in determining the way the data is stored.
A must read is Datatypes In SQLite Version 3
You may also find How flexible/restricive are SQLite column types?
You may be able to resolve this by using a CHECK constraint CREATE TABLE or by using a TRIGGER or multiple TRIGGERs.
You could format the number(s) appropriately when they are displayed.
You could utilise the round(x,y) function Core Functions
I have a column containing user entry descriptions, these descriptions can be anything however i do need them sorted into a logical order.
The text can be anything like
16 to 26 months
40 to 60 months
Literacy
Mathematics
When i order these in sql statement the text items return fine. However any beginning with numbers come back in an order not logical
i.e.
16 to 26 months
will be before
8 to 20 months
i understand why as it takes first character etc but don't know how to alter sql statement (using sqlite) to improve the performance without messing up the entries beginning with text
When i cast to numeric the numbers are fine the items beginning with text go wrong
Thanks
What you need is sorting the values in "natural order". To achieve this you will need to implement your own collating sequence; SQLite doesn't provide one for this case.
There are some questions (and answers) regarding this topic here on SO, but they are for other RDBMS. The best I could find in a quick search was this:
http://wiki.ozanh.com/doku.php?id=python:database:sqlite:how_to_natural_sort
You should think about improving your table schema, e. g. splitting the period into separate integer columns (monthsMin, monthsMax) instead of using text, which would make sorting much easier. You can always build a string from this values if necessary.
I have a TEXT column called "time" in a table meal and in a table pain which is TEXT formatted as YYYY-MM-DDTHH:MM. I'm trying to search for other times that are within 12 hours of a given time, although I can't figure out how to do that.
I've tried testing
WHERE pain.time < meal.time + "1:00" AND pain.time > meal.time
but this approach alters the year instead of the hour. I also tried testing the same query adding "0000-00-00T01:00", but it doesn't seem to do anything.
I'm not sure what else to test.
SQLite has no built-in date/time data type, so you have to use either numbers or strings and handle them correctly.
To do calculations, you have to either do them directly on the numerical value (which might require conversions into a number and back), or use the modifiers of the built-in date/time functions:
... WHERE meal.time BETWEEN datetime(pain.time, '-12 hours') AND pain.time
I have a SQLite3 table with a column having format DECIMAL(7,2), but whenever I select rows with values not having a non-zero 2nd decimal place (eg. 3.00 or 3.10), the result always has trailing zero(s) missing (eg. 3 or 3.1). Is there any way that I can apply a formatting function in the SELECT statement so that I get the required 2dp? I have tried ROUND(), but this has no effect. Otherwise I have to keep converting the resulting column values into the required format for display (using Python in my case) every time I do a SELECT statement, which is a real pain.
I don't even mind if the result is string instead of numeric, as long as it has the right number of decimal places.
Any help would be appreciated.
Alan
SQLite internally uses IEEE binary floating point arithmetic, which truly does not lend itself well to maintaining a particular number of decimals. To get that type of decimal handling would require one of:
Fixed point math, or
IEEE decimal floating point (rather uncommon), or
Handling everything as strings.
Formatting the values (converting from floating point to string) after extraction is the simplest way to implement things. You could even hide that inside some sort of wrapper so that the rest of the code doesn't have to deal with the consequences. But if you're going to do arithmetic on the value afterwards then you're better off not formatting and instead working with the value as returned by the query, because the format and reconvert back to binary floating point (which Python uses, just like the vast majority of other modern languages) loses lots of information in the reduced precision.