having

having子句总是跟在group by或者context by后,用来将结果进行过滤,只返回满足指定条件组结果。

  • 如果having用在group by后,having只可与聚合函数一起使用,结果为符合聚合函数条件的每组产生一条记录。

  • 如果having用在context by后,并且只与聚合函数一起使用,结果是符合聚合函数条件的分组,每组记录与输入数据中记录数一致。

  • 如果having用在context by后,与非聚合函数一起使用,结果是符合指定条件的分组。

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
select sum(qty) as totalqty from t1 group by sym having sum(qty)>10000;
sym totalqty
C 14800
IBM 12200
select * from t1 context by sym having count(sym)>2 and sum(qty)>10000;
timestamp sym qty price
09:34:07 C 2200 49.6
09:34:16 C 1300 50.76
09:34:26 C 2500 50.32
09:38:12 C 8800 51.29
select * from t1 context by sym having rank(qty)>1;
timestamp sym qty price
09:34:26 C 2500 50.32
09:38:12 C 8800 51.29
09:36:59 MS 3200 30.02
 
select * from t1 context by sym having rank(qty)>1 and sum(qty)>10000;
timestamp sym qty price
09:34:26 C 2500 50.32
09:38:12 C 8800 51.29

在select语句中,对符合having条件的记录进行计算:

select *, min(qty) from t1 context by sym having rank(qty)>1;
timestamp sym qty price min_qty
09:34:26 C 2500 50.32 1300
09:38:12 C 8800 51.29 1300
09:36:59 MS 3200 30.02 1900

top语句可以与context by语句和having语句一起使用。

select top 2 * from t1 context by sym having sum(qty)>8000;
timestamp sym qty price
09:34:07 C 2200 49.6
09:34:16 C 1300 50.76
09:32:47 IBM 6800 174.97
09:35:26 IBM 5400 175.23