如何使用SAP HANA Web-based Development工具进行SQLScript练习
小编给大家分享一下如何使用SAP HANA Web-based Development工具进行SQLScript练习，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！
通过csv文件提供的数据库表内容：
links.csv的格式：
movies.csv格式，一个movie可以有多种风格(genres)，通过|分隔：
ratings.csv:
用户给movie打得分：
tags.csv：movie的标签
练习一：
列出四张表的总记录数：
select 'links' as "table name", count(1) as "row count" from "MOVIELENS"."public.aa.movielens.hdb::data.LINKS"
union all
select 'movies' as "table name", count(1) as "row count" from "MOVIELENS"."public.aa.movielens.hdb::data.MOVIES"
union all
select 'ratings' as "table name", count(1) as "row count" from "MOVIELENS"."public.aa.movielens.hdb::data.RATINGS"
union all
select 'tags' as "table name", count(1) as "row count" from "MOVIELENS"."public.aa.movielens.hdb::data.TAGS";
执行结果：
练习2：计算总共9125部电影，一共包含多少艺术类别？
DO
BEGIN
DECLARE genreArray NVARCHAR(255) ARRAY;
DECLARE tmp NVARCHAR(255);
DECLARE idx INTEGER;
DECLARE sep NVARCHAR(1) := '|';
DECLARE CURSOR cur FOR SELECT DISTINCT "GENRES" FROM "MOVIELENS"."public.aa.movielens.hdb::data.MOVIES";
DECLARE genres NVARCHAR (255) := '';
idx := 1;
FOR cur_row AS cur() DO
SELECT cur_row."GENRES" INTO genres FROM DUMMY;
tmp := :genres;
WHILE LOCATE(:tmp,:sep) > 0 DO
genreArray[:idx] := SUBSTR_BEFORE(:tmp,:sep);
tmp := SUBSTR_AFTER(:tmp,:sep);
idx := :idx + 1;
END WHILE;
genreArray[:idx] := :tmp;
END FOR;
genreList = UNNEST(:genreArray) AS ("GENRE");
SELECT "GENRE" FROM :genreList GROUP BY "GENRE";
END;
执行结果，总共包含18种：
练习3：计算每种艺术类别总共包含多少部电影：
DO
BEGIN
DECLARE genreArray NVARCHAR(255) ARRAY;
DECLARE tmp NVARCHAR(255);
DECLARE idx INTEGER;
DECLARE sep NVARCHAR(1) := '|';
DECLARE CURSOR cur FOR SELECT DISTINCT "GENRES" FROM "MOVIELENS"."public.aa.movielens.hdb::data.MOVIES";
DECLARE genres NVARCHAR (255) := '';
idx := 1;
FOR cur_row AS cur() DO
SELECT cur_row."GENRES" INTO genres FROM DUMMY;
tmp := :genres;
WHILE LOCATE(:tmp,:sep) > 0 DO
genreArray[:idx] := SUBSTR_BEFORE(:tmp,:sep);
tmp := SUBSTR_AFTER(:tmp,:sep);
idx := :idx + 1;
END WHILE;
genreArray[:idx] := :tmp;
END FOR;
genreList = UNNEST(:genreArray) AS ("GENRE");
SELECT "GENRE", count(1) FROM :genreList GROUP BY "GENRE";
END;
练习4：列出每部电影包含的风格数目：
SELECT
"MOVIEID"
, "TITLE"
, OCCURRENCES_REGEXPR('[|]' IN GENRES) + 1 "GENRE_COUNT"
, "GENRES"
FROM "MOVIELENS"."public.aa.movielens.hdb::data.MOVIES"
ORDER BY "GENRE_COUNT" ASC;
练习5：罗列出每部电影的风格分布情况
SELECT
"GENRE_COUNT"
, COUNT(1)
FROM (
SELECT
OCCURRENCES_REGEXPR('[|]' IN "GENRES") + 1 "GENRE_COUNT"
FROM "MOVIELENS"."public.aa.movielens.hdb::data.MOVIES"
)
GROUP BY "GENRE_COUNT" ORDER BY "GENRE_COUNT";
比如至少拥有1个风格的电影，有2793部，2个风格的电影有3039部，等等。
练习6：计算movie的rating分布情况
SELECT DISTINCT
MIN("RATING_COUNT") OVER( ) AS "MIN",
MAX("RATING_COUNT") OVER( ) AS "MAX",
AVG("RATING_COUNT") OVER( ) AS "AVG",
SUM("RATING_COUNT") OVER( ) AS "SUM",
MEDIAN("RATING_COUNT") OVER( ) AS "MEDIAN",
STDDEV("RATING_COUNT") OVER( ) AS "STDDEV",
COUNT(*) OVER( ) AS "CATEGORY_COUNT"
FROM (
SELECT "MOVIEID", COUNT(1) as "RATING_COUNT"
FROM "MOVIELENS"."public.aa.movielens.hdb::data.RATINGS"
GROUP BY "MOVIEID"
)
GROUP BY "RATING_COUNT";
明细情况：
SELECT "RATING_COUNT", COUNT(1) as "MOVIE_COUNT"
FROM (
SELECT "MOVIEID", COUNT(1) as "RATING_COUNT"
FROM "MOVIELENS"."public.aa.movielens.hdb::data.RATINGS"
GROUP BY "MOVIEID"
)
GROUP BY "RATING_COUNT" ORDER BY "RATING_COUNT" asc;
比如有397部电影的用户投票数为5票
练习7：统计用户投票情况
SELECT "RATING_COUNT", COUNT(1) as "USER_COUNT"
FROM (
SELECT "USERID", COUNT(1) as "RATING_COUNT"
FROM "MOVIELENS"."public.aa.movielens.hdb::data.RATINGS"
GROUP BY "USERID"
)
GROUP BY "RATING_COUNT" ORDER BY 1 DESC;
有一位用户投了2391票，一位用户投了1868票：
练习8：统计用户投票得分情况
SELECT "RATING", COUNT(1) as "RATING_COUNT"
FROM "MOVIELENS"."public.aa.movielens.hdb::data.RATINGS"
GROUP BY "RATING" ORDER BY 1 DESC;
有15095份用户投票，打的分数是5分
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