views, having clause, roll up, sql modes

Author: mayankSystems

src/main/java/dev/mayankg/db_concepts/mysql/exc05/sql_views.sql

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+-- FULL JOINED REVIEW QUERY (USED FREQUENTLY)
+SELECT title, released_year, genre, rating, first_name, last_name
+FROM reviews
+    JOIN series ON series.id = reviews.series_id
+    JOIN reviewers ON reviewers.id = reviews.reviewer_id;
+
+-- CREATING A VIEW FOR THE ABOVE QUERY
+CREATE VIEW full_reviews AS
+SELECT title, released_year, genre, rating, first_name, last_name
+FROM reviews
+    JOIN series ON series.id = reviews.series_id
+    JOIN reviewers ON reviewers.id = reviews.reviewer_id;
+
+-- USING THE VIEW LIKE A VIRTUAL TABLE
+SELECT * FROM full_reviews;
+
+-- CREATING A VIEW TO ORDER SERIES BY YEAR (ASCENDING)
+CREATE VIEW ordered_series AS
+SELECT * FROM series
+ORDER BY released_year;
+
+-- REPLACING THE VIEW TO ORDER BY YEAR (DESCENDING)
+CREATE OR REPLACE VIEW ordered_series AS
+SELECT * FROM series
+ORDER BY released_year DESC;
+
+-- ALTERING EXISTING VIEW TO CHANGE SORT ORDER
+ALTER VIEW ordered_series AS
+SELECT * FROM series
+ORDER BY released_year;
+
+-- DROPPING THE VIEW
+DROP VIEW ordered_series;
+
+-- AGGREGATE: AVERAGE RATINGS FOR SERIES WITH MORE THAN 1 REVIEW
+SELECT
+    title,
+    AVG(rating) AS avg_rating,
+    COUNT(rating) AS review_count
+FROM full_reviews
+GROUP BY title
+HAVING COUNT(rating) > 1;
+
+-- AGGREGATE WITH ROLLUP: AVERAGE RATING PER TITLE
+SELECT
+    title,
+    AVG(rating) AS avg_rating
+FROM full_reviews
+GROUP BY title WITH ROLLUP;
+
+-- AGGREGATE WITH ROLLUP: REVIEW COUNT PER TITLE
+SELECT
+    title,
+    COUNT(rating) AS review_count
+FROM full_reviews
+GROUP BY title WITH ROLLUP;
+
+-- MULTI-COLUMN GROUPING WITH ROLLUP: AVG RATINGS PER REVIEWER/YEAR/GENRE
+SELECT
+    first_name,
+    released_year,
+    genre,
+    AVG(rating) AS avg_rating
+FROM full_reviews
+GROUP BY released_year, genre, first_name WITH ROLLUP;
+
+-- To View Modes:
+SELECT @@GLOBAL.sql_mode;
+SELECT @@SESSION.sql_mode;
+
+-- To Set Them:
+SET GLOBAL sql_mode = 'modes';
+SET SESSION sql_mode = 'modes';