Merge pull request #5377 from BohuTANG/doc-retention

chore(doc): better retention example

docs/doc/30-reference/20-functions/10-aggregate-functions/aggregate-retention.md

@@ -29,32 +29,31 @@ The array of 1 or 0.
 ## Examples
 
 ```
-CREATE TABLE retention_test(date DATE, uid INT) ENGINE = Memory;
+CREATE TABLE retention_test(date DATE, uid INT);
 INSERT INTO retention_test SELECT '2018-08-06', number FROM numbers(80);
-INSERT INTO retention_test SELECT '2018-08-07', number FROM numbers(50);
+INSERT INTO retention_test SELECT '2018-08-07', number FROM numbers(70);
 INSERT INTO retention_test SELECT '2018-08-08', number FROM numbers(60);
 ```
 
 ```
-SELECT sum(get(r, 0)::TINYINT) as r1, sum(get(r, 1)::TINYINT) as r2 FROM (SELECT uid, retention(date = '2018-08-06', date = '2018-08-07') AS r FROM retention_test WHERE date = '2018-08-06' or date = '2018-08-07' GROUP BY uid);
+SELECT sum(r[0]::TINYINT) as r1, sum(r[1]::TINYINT) as r2 FROM (SELECT uid, retention(date = '2018-08-06', date = '2018-08-07') AS r FROM retention_test WHERE date = '2018-08-06' or date = '2018-08-07' GROUP BY uid);
 +------+------+
 | r1   | r2   |
 +------+------+
-|   80 |   50 |
+|   80 |   70 |
 +------+------+
 
-SELECT sum(get(r, 0)::TINYINT) as r1, sum(get(r, 1)::TINYINT) as r2 FROM (SELECT uid, retention(date = '2018-08-06', date = '2018-08-08') AS r FROM retention_test WHERE date = '2018-08-06' or date = '2018-08-08' GROUP BY uid);
+SELECT sum(r[0]::TINYINT) as r1, sum(r[1]::TINYINT) as r2 FROM (SELECT uid, retention(date = '2018-08-06', date = '2018-08-08') AS r FROM retention_test WHERE date = '2018-08-06' or date = '2018-08-08' GROUP BY uid);
 +------+------+
 | r1   | r2   |
 +------+------+
 |   80 |   60 |
 +------+------+
 
-SELECT sum(get(r, 0)::TINYINT) as r1, sum(get(r, 1)::TINYINT) as r2, sum(get(r, 2)::TINYINT) as r3 FROM (SELECT uid, retention(date = '2018-08-06', date = '2018-08-07', date = '2018-08-08') AS r FROM retention_test GROUP BY uid);
+SELECT sum(r[0]::TINYINT) as r1, sum(r[1]::TINYINT) as r2, sum(get(r, 2)::TINYINT) as r3 FROM (SELECT uid, retention(date = '2018-08-06', date = '2018-08-07', date = '2018-08-08') AS r FROM retention_test GROUP BY uid);
 +------+------+------+
 | r1   | r2   | r3   |
 +------+------+------+
-|   80 |   50 |   60 |
+|   80 |   70 |   60 |
 +------+------+------+
-
 ```