Hi,
How do you create an empty table with columns defined pragmatically: c1, c2, c3,
This function does not work because I can’t figure out how to add a column. It’s not interpreting column name.
tbl:{ c:(“c” ,/: (string (1+til x))); t:( c1:“f”$()); f1:{[t;cname] t:update cname:0f from t; :t }; t:f1[t;c2]; :t }
q)t:(c1:0#0f)
q)t[`c2]:0#0f
q)t
c1 c2
or
q)t:![t;();0b;enlist[`c3]!enlist 0f]
q)t
c1 c2 c3
--------
http://code.kx.com/wiki/JB:QforMortals2/queries_q_sql#Functional_update
If you knew the column names and number, you could do;
q)flip select c1:0#0f,c2:0#0f from (0#`)!()
c1 c2
-----
Since the columns are dynamic, a functional select may be an approach;
q)parse"select c1:0#0f,c2:0#0f from (0#`)!()"
?
(!;(#;0;,`);())
()
0b
c1c2!((#;0;0f);(#;0;0f))
/giving…
q)0N!{kols:($"c",/:string til x)!0#'x#enlist 0f; flip?[(0#)!();();0b;kols]}10
+c0c1c2c3c4c5c6c7c8c9!(float$();float$();float$();float$();`flo..
c0 c1 c2 c3 c4 c5 c6 c7 c8 c9
/alternative approach
)!();x;{0#0f}]}$“c”,/:string[til 10]Is this what you were looking for?
Thanks,
Michael
f:{flip z!x#/:y$:" "}; //x is number of (null) rows; y are column types; z are column names
t:f[0;“BXHIJEFCSMDZUVTGNP”;BXHIJEFCSMDZUVTGNP];
meta t
c| t f a
-| -----
B| b
X| x
H| h
I| i
J| j
E| e
F| f
C| c
S| s
M| m
D| d
Z| z
U| u
V| v
T| t
G| g
N| n
P| p