数据库题目整理及详解英文版(五)
Preface when there is rain neither sun nor moon, the people actually do not think so. Perhaps there are seasonal climate not to be cold rain, let the sun or the cool side. Has the rain the night is otherwise a moonlit night no flavor. Some
Preface
when there is rain neither sun nor moon, the people actually do not think so.
Perhaps there are seasonal climate not to be cold rain, let the sun or the cool side.
Has the rain the night is otherwise a moonlit night no flavor.
Sometimes not reminiscent of Li Shangyin “when he cut a total of west window candle, but then when the famous hope of reunion among friends”
In the rain, fom the sky come the silk notes; here, quiet and comfortable.
Presentation
In this page, we will show the homework of the course of the Databases Technology in CMU. All of the questions we tested in the postgresql.
This section mainly is to practice the query operation of the SQL, include SQL view, index, etc. We also sure that all the sqls will pass in the mysql, sqlite… , this article also will provide the Chinese version in detail.
中文版
Question Details
In this homework you will have to write SQL queries to answer questions on a movie dataset, about movies and actors. The database contains two tables:
? movies(mid, title, year, num ratings, rating) , Primary key: mid
? play in(mid, name, cast position), Primary key: mid, name
The tables contain the obvious information: which actor played in what movie, at what position; for each movie, we have the title (eg., ’Gone with the wind’), year of production, count of rating reviews it received, and the average score of those ratings (a float in the range 0 to 10, with ’10’ meaning ’excellent’).
We will use Postgres, which is installed in the your own machines.
Question 1: Warm-up queries … … … … … … … … . [5 points]
(a) [2 points] Print all actors in the movie Quantum of Solace, sorted by cast position. Print only their names.
(b) [3 points] Print all movie titles that were released in 2002, with rating larger than 8 and with more than one rating (num ratings > 1).
Question 2: Find the star’s movies … … … … … … . . [5 points]
(a) [5 points] Print movie titles where Sean Connery was the star (i.e. he had position 1 in the cast). Sort the movie titles alphabetically.
Question 3: Popular actors … … … … … … … … . . [15 points]
(a) [8 points] We want to find the actors of the highest quality. We define their quality as the weighted average of the ratings of the movies they have played in (regardless of cast position), using the number of ratings for each movie as the
weight. In other words, we define the quality for a particular actor as
Print the names of the top 5 actors, according to the above metric. Break ties alphabetically.
(b) [7 points] Now we want to find the 5 most popular actors, in terms of number of ratings (regardless of positive or negative popularity). I.e, if actor ‘Smith’ played in 2 movies, with num ratings 10 and 15, then Smith’s popularity is 25 (=10+15). Print the top 5 actor names according to popularity. Again, break ties alphabetically.
Question 4: Most controversial actor … … … … … . [10 points]
(a) [10 points] We want to find the most controversial actor. As a measure of controversy, we define the maximum difference between the ratings of two movies that an actor has played in (regardless of cast position). That is, if actor ‘Smith’ played in a movie that got rating=1.2, and another that got rating=9.5, and all the other movies he played in, obtained scores within that range, then Smith’s contoversy score is 9.5-1.2= 8.3. Print the name of the top-most controversial actor - again, if there is a tie in first place, break it alphabetically.
Question 5: The minions … … … … … … … … … . [20 points]
(a) [20 points] Find the “minions” of Annette Nicole: Print the names of actors who only played in movies with her and never without her. The answer should not contain the name of Annette Nicole. Order the names alphabetically.
Question 6: High productivity … … … … … … … … [5 points]
(a) [5 points] Find the top 2 most productive years (by number of movies produced). Solve ties by preferring chronologically older years, and print only the years.
Question 7: Movies with similar cast … … … … … . [15 points]
(a) [8 points] Print the count of distinct pairs of movies that have at least one actor in common (ignoring cast position). Exclude self-pairs, and mirror-pairs.
(b) [7 points] Print the count of distinct pairs of moves that have at least two actors in common (again, ignoring cast position). Again, exclude self-pairs, and mirror pairs.
Question 8: Skyline query … … … … … … … … … [25 points]
(a) [25 points] We want to find a set of movies that have both high popularity (ie, high num ratings) as well as high quality (rating). No single movie may achieve both - in which case, we want the so-called Skyline query 2 . More specifically, we want all movies that are not “dominated” by any other movie:
Definition of domination : Movie “A” dominates movie “B” if movie “A” wins over movie “B”, on both criteria, or wins on one, and ties on the rest.
Figure 1 gives a pictorial example: the solid dots (’A’, ’D’, ’F’) are not dominated by any other dot, and thus form the skyline. All other dots are dominated by at least one other dot: e.g., dot ’B’ is dominated by dot ’A’, being inside the shaded rectangle that has ’A’ as the upper-right corner.
Figure 1: Illustration of Skyline and domination : ’A’ dominates all points in the shaded rectangle; ’A’, ’D’ and ’F’ form the skyline of this cloud of points.
Given the above description, print the title of all the movies on the skyline, along with the rating and the number of ratings.
Answer
we give the Postgres version in detail, we will see you can tranfer it easily in mysql or sqlite.
Initialization:
<code class=" hljs sql">## <span class="hljs-operator"><span class="hljs-keyword">drop</span> the <span class="hljs-keyword">table</span> <span class="hljs-keyword">if</span> <span class="hljs-keyword">exists</span> <span class="hljs-keyword">drop</span> <span class="hljs-keyword">table</span> <span class="hljs-keyword">if</span> <span class="hljs-keyword">exists</span> movies <span class="hljs-keyword">cascade</span>;</span> <span class="hljs-operator"><span class="hljs-keyword">drop</span> <span class="hljs-keyword">table</span> <span class="hljs-keyword">if</span> <span class="hljs-keyword">exists</span> play_in <span class="hljs-keyword">cascade</span>;</span> ## <span class="hljs-operator"><span class="hljs-keyword">create</span> tables movies <span class="hljs-keyword">and</span> play_in <span class="hljs-keyword">create</span> <span class="hljs-keyword">table</span> movies ( mid <span class="hljs-keyword">integer</span> <span class="hljs-keyword">PRIMARY</span> <span class="hljs-keyword">KEY</span>, title <span class="hljs-keyword">varchar</span>(<span class="hljs-number">200</span>), <span class="hljs-keyword">year</span> <span class="hljs-keyword">integer</span>, num_ratings <span class="hljs-keyword">integer</span>, rating <span class="hljs-keyword">real</span>);</span> <span class="hljs-operator"><span class="hljs-keyword">create</span> <span class="hljs-keyword">table</span> play_in ( mid <span class="hljs-keyword">integer</span> <span class="hljs-keyword">references</span> movies, name <span class="hljs-keyword">varchar</span>(<span class="hljs-number">100</span>), cast_position <span class="hljs-keyword">integer</span>, <span class="hljs-keyword">PRIMARY</span> <span class="hljs-keyword">KEY</span>(mid, name));</span> <span class="hljs-operator"><span class="hljs-keyword">create</span> index mid <span class="hljs-keyword">on</span> movies(mid);</span></code>
Insert Values
Insert into some values into the table movies and play_in,
you will find the datas just in the follow links in my 360 yunFiles:
https://yunpan.cn/cSfLzxQApRXSi password: f3ab
<code class=" hljs rust">## <span class="hljs-keyword">use</span> <span class="hljs-string">"copy"</span> in Postgres \<span class="hljs-keyword">copy</span> movies from <span class="hljs-string">'~/data/movie_processed.dat'</span>; \<span class="hljs-keyword">copy</span> play_in from <span class="hljs-string">'~/data/movie_actor_processed.dat'</span>; ## <span class="hljs-keyword">if</span> you <span class="hljs-keyword">use</span> other databases(mysql, sqlite), you can <span class="hljs-keyword">use</span> the sql statement: <span class="hljs-string">"insert into ... valuse()"</span> </code>
The flowing image show the test infos in my ubuntu os:
Solution 1
<code class=" hljs asciidoc">(a) SELECT name FROM play<span class="hljs-emphasis">_in p, movies m WHERE p.mid = m.mid and m.title=’Quantum of Solace’ ORDER BY p.cast_</span>position; ## (a) Result just like this: <span class="hljs-header">name ------------------------------</span> Daniel Craig Olga Kurylenko Mathieu Amalric Judi Dench Giancarlo Giannini Gemma Arterton Jeffrey Wright David Harbour Jesper Christensen Anatole Taubman Rory Kinnear Tim Pigott-Smith Fernando Guillen-Cuervo Jesus Ochoa Glenn Foster Paul Ritter Simon Kassianides Stana Katic Lucrezia Lante della Rove... Neil Jackson Oona Chaplin (21 rows) (b) SELECT title FROM movies WHERE year = 2002 and rating>8 and num<span class="hljs-emphasis">_ratings>1; </span>## (b) Result just like this: <span class="hljs-header">title ---------------------------------------</span> The Lord of the Rings: The Two Towers Cidade de Deus Mou gaan dou (3 rows) </code>
The flowing image show the test solution 1 infos in my ubuntu os:
Solution 2
<code class=" hljs vbnet"><span class="hljs-keyword">SELECT</span> title <span class="hljs-keyword">from</span> movies m, play_in p <span class="hljs-keyword">WHERE</span> m.<span class="hljs-keyword">mid</span> = p.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> name = ’Sean Connery’ <span class="hljs-keyword">and</span> cast_position = <span class="hljs-number">1</span> <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> title; <span class="hljs-preprocessor">## Result just like this:</span> title --------------------------------------- Der Name der Rose Diamonds Are Forever Dr. No Entrapment Finding Forrester First Knight <span class="hljs-keyword">From</span> Russia <span class="hljs-keyword">with</span> Love Goldfinger Never Say Never Again The Hunt <span class="hljs-keyword">for</span> Red October The League <span class="hljs-keyword">of</span> Extraordinary Gentlemen Thunderball You Only Live Twice (<span class="hljs-number">13</span> rows)</code>
The flowing image show the test solution 2 infos in my ubuntu os:
Solution 3
<code class=" hljs sql">(a) <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> WeigthedRatings;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> WeightedRatings <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> name, <span class="hljs-aggregate">SUM</span>(rating*num_ratings)/<span class="hljs-aggregate">SUM</span>(num_ratings) <span class="hljs-keyword">AS</span> WeightedRating <span class="hljs-keyword">FROM</span> movies m, play_in p <span class="hljs-keyword">WHERE</span> m.mid = p.mid <span class="hljs-keyword">GROUP</span> <span class="hljs-keyword">BY</span>(name);</span> <span class="hljs-operator"><span class="hljs-keyword">SELECT</span> name <span class="hljs-keyword">FROM</span> WeightedRatings <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> WeightedRating <span class="hljs-keyword">DESC</span>, name <span class="hljs-keyword">ASC</span> LIMIT <span class="hljs-number">5</span>;</span> ## (a) Result just like this: name <span class="hljs-comment">-----------------------</span> Adam Kalesperis Aidan Feore Aleksandr Kajdanovsky Alexander Kaidanovsky Alisa Frejndlikh (5 rows) (b) <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> ActorSumRatings;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> ActorSumRatings <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> name, <span class="hljs-aggregate">SUM</span>(num_ratings) <span class="hljs-keyword">as</span> popularity <span class="hljs-keyword">FROM</span> play_in p, movies m <span class="hljs-keyword">WHERE</span> p.mid = m.mid <span class="hljs-keyword">GROUP</span> <span class="hljs-keyword">BY</span> name;</span> <span class="hljs-operator"><span class="hljs-keyword">SELECT</span> name <span class="hljs-keyword">from</span> ActorSumRatings <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> popularity <span class="hljs-keyword">DESC</span>, name <span class="hljs-keyword">ASC</span> LIMIT <span class="hljs-number">5</span>;</span> ## (b) Result just like this: name <span class="hljs-comment">----------------------</span> Johnny Depp Alan Rickman Orlando Bloom Helena Bonham Carter Matt Damon (5 rows)</code>
The flowing images show the test solution 3 infos in my ubuntu os:
Solution 4
<code class=" hljs sql"><span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> RatingGap;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> RatingGap <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> p1.name, <span class="hljs-aggregate">MAX</span>(ABS(m1.rating-m2.rating)) <span class="hljs-keyword">as</span> Gap <span class="hljs-keyword">FROM</span> play_in p1, play_in p2, movies m1, movies m2 <span class="hljs-keyword">WHERE</span> p1.mid = m1.mid <span class="hljs-keyword">and</span> p2.mid = m2.mid <span class="hljs-keyword">and</span> p1.name = p2.name <span class="hljs-keyword">GROUP</span> <span class="hljs-keyword">BY</span>(p1.name);</span> <span class="hljs-operator"><span class="hljs-keyword">SELECT</span> name <span class="hljs-keyword">FROM</span> RatingGap <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span>(Gap) <span class="hljs-keyword">DESC</span> LIMIT <span class="hljs-number">1</span>;</span> ## Result just like this: name <span class="hljs-comment">---------------</span> John Travolta (1 row)</code>
The flowing image show the test solution 4 infos in my ubuntu os:
Solution 5
<code class=" hljs sql"><span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> MastersMovies <span class="hljs-keyword">CASCADE</span>;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> MastersMovies <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> m.mid,m.title <span class="hljs-keyword">FROM</span> movies m, play_in p <span class="hljs-keyword">WHERE</span> m.mid = p.mid <span class="hljs-keyword">and</span> p.name = ’Annette Nicole’;</span> <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> CoActors;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> CoActors <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">DISTINCT</span> name <span class="hljs-keyword">FROM</span> MastersMovies m , play_in p <span class="hljs-keyword">WHERE</span> p.mid = m.mid;</span> <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> Combinations;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> Combinations <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> name,mid <span class="hljs-keyword">FROM</span> MastersMovies , CoActors;</span> <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> NonExistent;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> NonExistent <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> * <span class="hljs-keyword">FROM</span> Combinations <span class="hljs-keyword">EXCEPT</span> (<span class="hljs-keyword">SELECT</span> name, mid <span class="hljs-keyword">FROM</span> play_in);</span> <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> PotentialResults;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> PotentialResults <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> * <span class="hljs-keyword">from</span> CoActors <span class="hljs-keyword">EXCEPT</span> (<span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">distinct</span>(name) <span class="hljs-keyword">FROM</span> NonExistent);</span> <span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> NotMastersMovies;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> NotMastersMovies <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> m.mid <span class="hljs-keyword">FROM</span> movies m <span class="hljs-keyword">EXCEPT</span> (<span class="hljs-keyword">SELECT</span> mid <span class="hljs-keyword">FROM</span> MastersMovies);</span> <span class="hljs-operator"><span class="hljs-keyword">SELECT</span> * <span class="hljs-keyword">from</span> PotentialResults <span class="hljs-keyword">WHERE</span> name <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> (<span class="hljs-keyword">SELECT</span> name <span class="hljs-keyword">FROM</span> play_in p, NotMastersMovies m <span class="hljs-keyword">WHERE</span> m.mid = p.mid <span class="hljs-keyword">UNION</span> <span class="hljs-keyword">SELECT</span> ’Annette Nicole’ ) <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> name;</span> ## Result just like this: name <span class="hljs-comment">-----------------</span> Christian Perry (1 row) </code>
The flowing image show the test solution 5 infos in my ubuntu os:
Solution 6
<code class=" hljs sql"><span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> MoviesPerYear;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> MoviesPerYear <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">year</span>, <span class="hljs-aggregate">COUNT</span>(title) num_movies <span class="hljs-keyword">FROM</span> MOVIES <span class="hljs-keyword">GROUP</span> <span class="hljs-keyword">BY</span>(<span class="hljs-keyword">year</span>);</span> <span class="hljs-operator"><span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">year</span> <span class="hljs-keyword">from</span> MoviesPerYear <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> num_movies <span class="hljs-keyword">DESC</span> LIMIT <span class="hljs-number">2</span>;</span> ## Result just like this: year <span class="hljs-comment">------</span> 2006 2007 (2 rows)</code>
The flowing image show the test solution 6 infos in my ubuntu os:
Solution 7
<code class=" hljs vbnet">(a) <span class="hljs-keyword">SELECT</span> COUNT(*) <span class="hljs-keyword">FROM</span> (<span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">DISTINCT</span> m1.<span class="hljs-keyword">mid</span>, m2.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">FROM</span> movies m1, movies m2, play_in p1, play_in p2 <span class="hljs-keyword">WHERE</span> m1.<span class="hljs-keyword">mid</span> > m2.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> m1.<span class="hljs-keyword">mid</span> = p1.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> m2.<span class="hljs-keyword">mid</span> = p2.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> p1.name = p2.name) <span class="hljs-keyword">AS</span> count; <span class="hljs-preprocessor">## (a) Result just like this:</span> count -------- <span class="hljs-number">104846</span> (<span class="hljs-number">1</span> row) (b) <span class="hljs-keyword">SELECT</span> COUNT(*) <span class="hljs-keyword">FROM</span> (<span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">DISTINCT</span> m1.<span class="hljs-keyword">mid</span>, m2.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">FROM</span> movies m1, movies m2, play_in p1, play_in p2, play_in p3, play_in p4 <span class="hljs-keyword">WHERE</span> m1.<span class="hljs-keyword">mid</span> > m2.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> m1.<span class="hljs-keyword">mid</span> = p1.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> m2.<span class="hljs-keyword">mid</span> = p2.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> m1.<span class="hljs-keyword">mid</span> = p3.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> m2.<span class="hljs-keyword">mid</span> = p4.<span class="hljs-keyword">mid</span> <span class="hljs-keyword">and</span> p2.name <> p4.name <span class="hljs-keyword">and</span> p1.name = p2.name <span class="hljs-keyword">and</span> p3.name = p4.name) <span class="hljs-keyword">AS</span> count; <span class="hljs-preprocessor">## (b) Result just like this:</span> count ------- <span class="hljs-number">6845</span> (<span class="hljs-number">1</span> row)</code>
The flowing image show the test solution 7 infos in my ubuntu os:
Solution 8
<code class=" hljs sql"><span class="hljs-operator"><span class="hljs-keyword">DROP</span> <span class="hljs-keyword">VIEW</span> <span class="hljs-keyword">IF</span> <span class="hljs-keyword">EXISTS</span> Dominated;</span> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">VIEW</span> Dominated <span class="hljs-keyword">AS</span> <span class="hljs-keyword">SELECT</span> <span class="hljs-keyword">DISTINCT</span> m2.mid, m2.title,m2.num_ratings, m2.rating <span class="hljs-keyword">FROM</span> movies m1, movies m2 <span class="hljs-keyword">WHERE</span> m2.rating<=m1.rating <span class="hljs-keyword">and</span> m2.num_ratings<=m1.num_ratings <span class="hljs-keyword">and</span> <span class="hljs-keyword">NOT</span> (m2.rating = m1.rating <span class="hljs-keyword">and</span> m2.num_ratings=m1.num_ratings);</span> <span class="hljs-operator"><span class="hljs-keyword">SELECT</span> title,num_ratings,rating <span class="hljs-keyword">FROM</span> movies <span class="hljs-keyword">EXCEPT</span> (<span class="hljs-keyword">SELECT</span> title,num_ratings,rating <span class="hljs-keyword">FROM</span> Dominated);</span> </code>
The flowing image show the test solution 8 infos in my ubuntu os:
Reference
[1] http://www.ruanyifeng.com/blog/2013/12/getting_started_with_postgresql.html
[2] http://www.postgresql.org/docs/
[3] http://www.cs.cmu.edu/~epapalex/15415S14/PostgreSQLReadme.htm
[4] http://www.cs.cmu.edu/~christos/courses/

ホットAIツール

Undresser.AI Undress
リアルなヌード写真を作成する AI 搭載アプリ

AI Clothes Remover
写真から衣服を削除するオンライン AI ツール。

Undress AI Tool
脱衣画像を無料で

Clothoff.io
AI衣類リムーバー

AI Hentai Generator
AIヘンタイを無料で生成します。

人気の記事

ホットツール

メモ帳++7.3.1
使いやすく無料のコードエディター

SublimeText3 中国語版
中国語版、とても使いやすい

ゼンドスタジオ 13.0.1
強力な PHP 統合開発環境

ドリームウィーバー CS6
ビジュアル Web 開発ツール

SublimeText3 Mac版
神レベルのコード編集ソフト(SublimeText3)

ホットトピック









Go 言語は、効率的かつ簡潔で習得が容易なプログラミング言語であり、同時プログラミングやネットワーク プログラミングに優れているため、開発者に好まれています。実際の開発ではデータベースの操作が欠かせませんが、今回はGo言語を使ってデータベースの追加・削除・変更・クエリ操作を実装する方法を紹介します。 Go 言語では、データベースを操作するために通常、よく使用される SQL パッケージや gorm などのサードパーティ ライブラリを使用します。ここでは SQL パッケージを例として、データベースの追加、削除、変更、クエリ操作を実装する方法を紹介します。 MySQL データベースを使用していると仮定します。

Hibernate ポリモーフィック マッピングは、継承されたクラスをデータベースにマップでき、次のマッピング タイプを提供します。 join-subclass: 親クラスのすべての列を含む、サブクラス用の別個のテーブルを作成します。 table-per-class: サブクラス固有の列のみを含む、サブクラス用の別個のテーブルを作成します。 Union-subclass: join-subclass と似ていますが、親クラス テーブルがすべてのサブクラス列を結合します。

Apple の最新リリースの iOS18、iPadOS18、および macOS Sequoia システムでは、さまざまな理由で紛失または破損した写真やビデオをユーザーが簡単に回復できるように設計された重要な機能が写真アプリケーションに追加されました。この新機能では、写真アプリのツール セクションに「Recovered」というアルバムが導入され、ユーザーがデバイス上に写真ライブラリに含まれていない写真やビデオがある場合に自動的に表示されます。 「Recovered」アルバムの登場により、データベースの破損、カメラ アプリケーションが写真ライブラリに正しく保存されない、または写真ライブラリを管理するサードパーティ アプリケーションによって失われた写真やビデオに対する解決策が提供されます。ユーザーはいくつかの簡単な手順を実行するだけで済みます

HTML はデータベースを直接読み取ることはできませんが、JavaScript と AJAX を通じて実現できます。この手順には、データベース接続の確立、クエリの送信、応答の処理、ページの更新が含まれます。この記事では、JavaScript、AJAX、および PHP を使用して MySQL データベースからデータを読み取る実践的な例を示し、クエリ結果を HTML ページに動的に表示する方法を示します。この例では、XMLHttpRequest を使用してデータベース接続を確立し、クエリを送信して応答を処理することで、ページ要素にデータを埋め込み、データベースを読み取る HTML の機能を実現します。

MySQLi を使用して PHP でデータベース接続を確立する方法: MySQLi 拡張機能を含める (require_once) 接続関数を作成する (functionconnect_to_db) 接続関数を呼び出す ($conn=connect_to_db()) クエリを実行する ($result=$conn->query()) 閉じる接続 ( $conn->close())

PHP でデータベース接続エラーを処理するには、次の手順を使用できます。 mysqli_connect_errno() を使用してエラー コードを取得します。 mysqli_connect_error() を使用してエラー メッセージを取得します。これらのエラー メッセージをキャプチャしてログに記録することで、データベース接続の問題を簡単に特定して解決でき、アプリケーションをスムーズに実行できるようになります。

PHP は Web サイト開発で広く使用されているバックエンド プログラミング言語であり、強力なデータベース操作機能を備えており、MySQL などのデータベースとの対話によく使用されます。ただし、中国語の文字エンコーディングは複雑であるため、データベース内で中国語の文字化けを処理するときに問題が発生することがよくあります。この記事では、文字化けの一般的な原因、解決策、具体的なコード例を含め、データベース内の中国語の文字化けを処理するための PHP のスキルと実践方法を紹介します。文字化けの一般的な原因は、データベースの文字セット設定が正しくないことです。データベースの作成時に、utf8 や u などの正しい文字セットを選択する必要があります。

Golang でデータベース コールバック関数を使用すると、次のことを実現できます。 指定されたデータベース操作が完了した後にカスタム コードを実行します。追加のコードを記述せずに、個別の関数を通じてカスタム動作を追加します。コールバック関数は、挿入、更新、削除、クエリ操作に使用できます。コールバック関数を使用するには、sql.Exec、sql.QueryRow、または sql.Query 関数を使用する必要があります。
