I would like to add a forward slash in a field name in a table:
tab:([] yes/no:`yes`yes`no;num: 1 2 3);
I tried using `$"yes/no": but didnt work. any input?
Create a dictionary and use flip to create a table:
q)columns:(`$"yes/no";`num)
q)columnValues:(`yes`yes`no;1 2 3)
q)tab:flip columns!columnValues
q)tab
yes/no num
----------
yes 1
yes 2
no 3
Note that it is not good practice to name columns in this manner (you lose the ability to use qSQL) but can still access the columns by using a functional select:
q)select yes/no from tab
'/
[0] select yes/no from tab
^
q)?[tab;();0b;enlist[`$"yes/no"]!enlist[`$"yes/no"]]
yes/no
------
yes
yes
no
Related
I would like to delete all records for all tables in memory but still keep the schemas.
for example:
a:([]a:1 2;b:2 4);
b:([]c:2 3;d:3 5);
I wrote a function:
{[t] t::select from t where i = -1} each tables[]
this didnt work, so i tried
{[t] ![`t;enlist(=;`i;-1);0b;()]} each tables[]
didnt work either.
Any idea or better ways?
If you pass a global table name as a symbol, it removes all the rows, leaving an empty table
q)delete from `a
`a
q)a
a b
---
q)meta a
c| t f a
-| -----
a| j
b| j
To do it for all global tables in root name space
{delete from x} each tables[]
Your second attempt using function was close. You can achieve it via the following (functional form of the above):
![;();0b;`symbol$()] each tables[]
The first argument should be the symbol of the table for the same reason I mentioned before
The second argument should be an empty list as we want to delete all records (we do not want to delete where i=-1, as that would delete nothing)
The final argument (list of columns to delete) should be an empty symbol list instead of an empty general list.
Mark's solution is best for doing what you want rather than functional form. Just adding to your question on t failing as putting kdb code in comments is awkward.
Your functional form fails not because of the t but because your last argument is not a symbol list `$(). Also you would want to delete where i is > -1, not =
q){[t] ![t;enlist(>;`i;-1);0b;`$()]} each `d`t`q
`d`t`q
q)d
date sym time bid1 bsize1 bid2 bsize2 bid3 bsize3 ask1 asize1 ask2 asize2 ask..
-----------------------------------------------------------------------------..
q)t
date sym time src price size
----------------------------
q)q
date sym time src bid ask bsize asize
-------------------------------------
I would like to order a bpchar column in the following order (first order by a-z, then numbers):
abc
bcd
xrf/1
zyd
0/abc
0/bdc
0/efg
How could I accomplish that?
Thank you
Can't fully tell from your question what you actually want. If it is the first character of the string you want to check whether it's numeric or alphabet, you may use a CASE expression in ORDER BY like this.
select * FROM t ORDER BY
CASE
WHEN col ~ '^[a-zA-Z]' THEN 1
WHEN col ~ '^[0-9]' THEN 2
END,col;
Demo
I'm looking for a way to write functional select in KDB such that the where phrases is only apply if the column exists (on order to avoid error). If the column doesn't exist, it defaults to true.
I tried this but it didn't work
enlist(|;enlist(in;`colname;key flip table);enlist(in;`colname;filteredValues[`colname]));
I tried to write a simple boolean expression and use parse to get my functional form
(table[`colname] in values)|(not `colname in key flip table)
But kdb doesn't have short circuit so the left-hand expression is still evaluated despite the right-hand expression evaluating to true. This caused a weird output boolean$() which is a list of booleans all evaluating to false 0b
Any help is appreciated. Thanks!
EDIT 1: I have to join a series of condition with parameter specified in the dictionary filters
cond,:(,/) {[l;k] enlist(in;k;enlist l[k])}[filters]'[a:(key filters)]
Then I pass this cond on and it gets executed on a few different selects on different tables. How can I make sure that whatever conditional expression I put in place of enlist(in;k;enlist l[k] will only get evaluated as the select statement gets executed.
You can use the if-else conditional $ here to do what you want
For example:
q)$[`bid in cols`quotes;enlist (>;`bid;35);()]
> `bid 35
q)$[`bad in cols`quotes;enlist (>;`bad;35);()]
Note that in the second example, the return is an empty list, as this column isn't in quotes table
So you can put this into the functional select like so:
?[`quotes;$[`bid in cols`quotes;enlist (>;`bid;35);()];0b;()]
and the where clause will be applied the the column is present, otherwise no where clause will be applied:
q)count ?[`quotes;$[`bid in cols`quotes;enlist (>;`bid;35);()];0b;()]
541 //where clause applied, table filtered
q)count ?[`quotes;$[`bad in cols`quotes;enlist (>;`bad;35);()];0b;()]
1000 //where clause not applied, full table returned
Hope this helps
Jonathon
AquaQ Analytics
EDIT: If I'm understanding your updated question correctly, you might be able to do something a like the following. Firstly, let's define an example "filters" dictionary:
q)filters:`a`b`c!(1 2 3;"abc";`d`e`f)
q)filters
a| 1 2 3
b| a b c
c| d e f
So here we are assuming a few different columns of different types, for illustration purposes. You can build up your list of where clauses like so:
q)(in),'flip (key filters;value filters)
in `a 1 2 3
in `b "abc"
in `c `d`e`f
(this is equivalent to the code you had to generate cond, but it's a little neater & more efficient - you also have the values enlisted, which isn't necessary)
You could then use a vector conditional to generate your list of where clauses to apply to a given table e.g.
q)t:([] a:1 2 3 4 5 6;b:"adcghf")
q)?[key[filters] in cols[t];(in),'flip (key filters;value filters);count[filters]#()]
(in;`a;,1 2 3)
(in;`b;,"abc")
()
As you can see, in this example the table "t" has columns a and b, but not c. So using the vector conditional, you get the where clauses for a and b but not c.
Finally to actually apply this list of output where clauses to the table, you can make use of an over to apply each in turn:
q)l:?[key[filters] in cols[t];(in),'flip (key filters;value filters);count[filters]#()]
q){?[x;$[y~();y;enlist y];0b;()]}/[t;l]
a b
---
1 a
3 c
One thing to note here is that in the where clause of the functional select we need to check if y is an empty list - this is so we can enlist it if it is not an empty list
Hope this helps
I created a Postgresql full text search using 'german'. How can I configer, that when I search for "Bezirk", lines containing "Bez." are also a match? (And vice-versa)
#pozs is right. You need to use a synonym dictionary.
1 - In the directory $SHAREDIR/tsearch_data create the file german.syn with the following contents:
Bez Bezirk
2 - Execute the query:
CREATE TEXT SEARCH DICTIONARY german_syn (
template = synonym,
synonyms = german);
CREATE TEXT SEARCH CONFIGURATION german_syn(COPY='simple');
ALTER TEXT SEARCH CONFIGURATION german_syn
ALTER MAPPING FOR asciiword, asciihword, hword_asciipart,
word, hword, hword_part
WITH german_syn, german_stem;
Now you can test it. Execute queries:
test=# SELECT to_tsvector('german_syn', 'Bezirk') ## to_tsquery('german_syn', 'Bezirk & Bez');
?column?
----------
t
(1 row)
test=# SELECT to_tsvector('german_syn', 'Bez Bez.') ## to_tsquery('german_syn', 'Bezirk');
?column?
----------
t
(1 row)
Additional links:
PostgreSQL: A Full Text Search engine (expired)
Try using a wildcard in your search.
For example:
tableName.column LIKE 'Bez%'
The % will search for any letter or number after the Bez
Description is very vague to understand what you are trying to achieve, but it looks like you need simple pattern matching search as you looking for abbreviations (so need to do stemming like in Full Text Search). I would with pg_trgm for this purpose:
WITH t(word) AS ( VALUES
('Bez'),
('Bezi'),
('Bezir')
)
SELECT word, similarity(word, 'Bezirk') AS similarity
FROM t
WHERE word % 'Bezirk'
ORDER BY similarity DESC;
Result:
word | similarity
-------+------------
Bezir | 0.625
Bezi | 0.5
Bez | 0.375
(3 rows)
I wanted to test what happened if I replace a variable with a different data type:
clear
input id x0
1 1
2 13
3 .
end
list
save tabA, replace
clear
input id str5 x0
1 "1"
2 "23"
3 "33"
end
list
save tabB, replace
use tabA, clear
mmerge id using tabB, type(1:1) update replace
list
The result is:
+--------------------------------------------------+
| id x0 _merge |
|--------------------------------------------------|
1. | 1 1 in both, master agrees with using data |
2. | 2 13 in both, master agrees with using data |
3. | 3 . in both, master agrees with using data |
+--------------------------------------------------+
This seems very strange to me. I expected breakdown or disagreement. Is this a bug or am I missing something?
mmerge is user-written (Jeroen Weesie, SSC, 2002).
If you use the official merge in an up-to-date Stata, you will get what you expect.
. merge 1:1 id using tabB, update replace
x0 is str5 in using data
r(106);
I have not looked inside mmerge. My own guess is that what you see is a feature from the author's point of view, namely that it's not a problem if one variable is numeric and one variable is string so long as their contents agree. But why are you not using merge directly? There was a brief period several years ago when mmerge had some advantages over merge, but that's long past. BTW, I agree in wanting my merges to be very conservative and not indulgent on variable types.