exec

select子句总是生成一张表，即使只选择一列亦是如此。若需要生成一个标量或者一个向量，可使用exec子句。

当与pivot by 共同使用时，exec语句生成一个矩阵，详情参考 pivotBy。

例子

sym = `C`MS`MS`MS`IBM`IBM`C`C`C$SYMBOL
price= 49.6 29.46 29.52 30.02 174.97 175.23 50.76 50.32 51.29
qty = 2200 1900 2100 3200 6800 5400 1300 2500 8800
timestamp = [09:34:07,09:36:42,09:36:51,09:36:59,09:32:47,09:35:26,09:34:16,09:34:26,09:38:12]
t1 = table(timestamp, sym, qty, price);
t1;
timestamp sym qty price
09:34:07 C 2200 49.6
09:36:42 MS 1900 29.46
09:36:51 MS 2100 29.52
09:36:59 MS 3200 30.02
09:32:47 IBM 6800 174.97
09:35:26 IBM 5400 175.23
09:34:16 C 1300 50.76
09:34:26 C 2500 50.32
09:38:12 C 8800 51.29 
x = select count(price) from t1;
x;
count_price
9 
typestr x;
 
TABLE

y = exec count(price) from t1;
y;
 
9

typestr y;
 
INT

x = select price from t1;
x;
price
49.6
29.46
29.52
30.02
174.97
175.23
50.76
50.32
51.29 
typestr x;
 
TABLE
y = exec price from t1;
y;
 
[49.6,29.46,29.52,30.02,174.97,175.23,50.76,50.32,51.29]

typestr y;
 
FAST DOUBLE VECTOR

如果exec语句选择了多列，那么结果和select语句一致，为table类型。

y = exec price, qty from t1;
y;
price qty
49.6 2200
29.46 1900
29.52 2100
30.02 3200
174.97 6800
175.23 5400
50.76 1300
50.32 2500
51.29 8800 
typestr y;
 
TABLE