使用SAP HANA Web-based Development工具进行SQLScript练习

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