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 |