天书 kdb+之q语言

kdb+ 目前还在研究中,主要资料kx.code.com

trade:([]time:`time$();sym:`symbol$();price:`float$();size:`int$())

exec t from trade \"tsfi"
exec c from trade `time`sym`price`size

`trade insert(09:30:00.000;`a;10.75;100)
`trade insert(09:30:00.000;`b;10.75;100)
`trade insert(09:30:00.000;`c;10.75;100)

select sum size by sym from trade

AllClients:([]time:enlist `All; price:enlist `All),select time,price from trade
time              price
-----------------------
`All              `All
09:30:00.000;     10.75

client:([]GPNum:`int$();GPName:`symbol$())

`client insert(00055;`a11111)
`client insert(06666;`b22222)
`client insert(00009;`c22222)

$[exprcond;exprtrue;exprfalse]

$[exprcond;[exprtrue1;...];[exprfalse1;...]]

$[exprcond1;exprtrue1;...;exprcondn;exprtruen;exprfalse]

?[vb;exprtrue;exprfalse]

if[exprcond;expr1;...;exprn]

@[fmul;Largs;exprfail]

1)$[0=count t;(GPNum:enlist `$"N/A";GPName:enlist "No Clients Available");1=count t;t;(GPNum:enlist `All;GPName:enlist "All"),t]
t==0,执行(GPNum:enlist `$"N/A";GPName:enlist "No Clients Available");
t==1,执行t;
其他(GPNum:enlist `All;GPName:enlist "All"),t

2)$[55 in `$GPNum;(GPNum:enlist `$"N/A";GPName:enlist "No Clients Available");t]

t:select  GPNum,{$[`~`$x;y;y," (",x,")"]}'[string[GPNum];upper string[GPName]] from client

{$[`~`$x;y;y," (",x,")"]}[123;456]  `~`$x条件判断{......}本身是个匿名函数

delimit:{[strg]    if[not 10h=type strg;strg:string strg];    "|" vs strg    }
delimit "a|b|c"
if[not 10h=type strg;strg:string strg] 如果strg不为string,转换为string类型
"|" vs strg　以"|"分割strg，大部分不会出现错误，但为symbol时　"|" vs `$"a|b|c"

L:(1 2;3 4 5; 6)
L[0]　　　　　　　　1 2
L 0 2或L[0 2]　　　1 2  6
L[1;2]　　　　　　　5

f:{x*x}
f[0]　　　　　　　　0
f 0 2或f[0 2]　　　　0 4          

g:{x+y} g[1;2] 　　　3