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/

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蘋果公司最新發布的iOS18、iPadOS18以及macOSSequoia系統為Photos應用程式增添了一項重要功能,旨在幫助用戶輕鬆恢復因各種原因遺失或損壞的照片和影片。這項新功能在Photos應用的"工具"部分引入了一個名為"已恢復"的相冊,當用戶設備中存在未納入其照片庫的圖片或影片時,該相冊將自動顯示。 "已恢復"相簿的出現為因資料庫損壞、相機應用未正確保存至照片庫或第三方應用管理照片庫時照片和視頻丟失提供了解決方案。使用者只需簡單幾步

Hibernate多態映射可映射繼承類別到資料庫,提供以下映射類型:joined-subclass:為子類別建立單獨表,包含父類別所有欄位。 table-per-class:為子類別建立單獨資料表,僅包含子類別特有列。 union-subclass:類似joined-subclass,但父類別表聯合所有子類別列。

PHP處理資料庫連線報錯,可以使用下列步驟:使用mysqli_connect_errno()取得錯誤代碼。使用mysqli_connect_error()取得錯誤訊息。透過擷取並記錄這些錯誤訊息,可以輕鬆識別並解決資料庫連接問題,確保應用程式的順暢運作。

如何在PHP中使用MySQLi建立資料庫連線:包含MySQLi擴充(require_once)建立連線函數(functionconnect_to_db)呼叫連線函數($conn=connect_to_db())執行查詢($result=$conn->query())關閉連線( $conn->close())

可以透過使用gjson函式庫或json.Unmarshal函數將JSON資料儲存到MySQL資料庫中。 gjson函式庫提供了方便的方法來解析JSON字段,而json.Unmarshal函數需要一個目標類型指標來解組JSON資料。這兩種方法都需要準備SQL語句和執行插入操作來將資料持久化到資料庫中。

在Golang中使用資料庫回呼函數可以實現:在指定資料庫操作完成後執行自訂程式碼。透過單獨的函數新增自訂行為,無需編寫額外程式碼。回調函數可用於插入、更新、刪除和查詢操作。必須使用sql.Exec、sql.QueryRow或sql.Query函數才能使用回呼函數。

PHP連接資料庫指南:MySQL:安裝MySQLi擴展,建立連線(servername、username、password、dbname)。 PostgreSQL:安裝PgSQL擴展,建立連線(host、dbname、user、password)。 Oracle:安裝OracleOCI8擴展,建立連線(servername、username、password)。實戰案例:取得MySQL資料、PostgreSQL查詢、OracleOCI8更新記錄。

在C++中使用DataAccessObjects(DAO)函式庫連接和操作資料庫,包括建立資料庫連線、執行SQL查詢、插入新記錄和更新現有記錄。具體步驟為:1.包含必要的函式庫語句;2.開啟資料庫檔案;3.建立Recordset物件執行SQL查詢或操作資料;4.遍歷結果或依照特定需求更新記錄。
