{"id":420,"date":"2026-09-22T07:38:54","date_gmt":"2026-09-22T06:38:54","guid":{"rendered":"https:\/\/zajecia.tsadowski.pl\/?p=420"},"modified":"2026-10-12T13:28:50","modified_gmt":"2026-10-12T12:28:50","slug":"funkcje-agregujace-w-mysql-3","status":"publish","type":"post","link":"https:\/\/zajecia.tsadowski.pl\/index.php\/2026\/09\/22\/funkcje-agregujace-w-mysql-3\/","title":{"rendered":"Funkcje agreguj\u0105ce w MySQL"},"content":{"rendered":"<p>Funkcje agreguj\u0105ce pozwalaj\u0105 wykonywa\u0107 operacje na <strong>zbiorach danych<\/strong>, a nie tylko na pojedynczych rekordach. Dzi\u0119ki nim mo\u017cemy:<\/p>\n<ul>\n<li>podsumowywa\u0107 dane,<\/li>\n<li>liczy\u0107 rekordy,<\/li>\n<li>oblicza\u0107 warto\u015bci \u015brednie,<\/li>\n<li>znajdowa\u0107 minimum i maksimum.<\/li>\n<\/ul>\n<p>S\u0105 one niezb\u0119dne do budowy raport\u00f3w, analiz i zapyta\u0144 statystycznych.\nW tej lekcji om\u00f3wimy pi\u0119\u0107 najcz\u0119\u015bciej u\u017cywanych funkcji:<\/p>\n<ul>\n<li><code>COUNT()<\/code><\/li>\n<li><code>SUM()<\/code><\/li>\n<li><code>AVG()<\/code><\/li>\n<li><code>MIN()<\/code><\/li>\n<li><code>MAX()<\/code><\/li>\n<\/ul>\n<hr \/>\n<h2>Dane do cwiczen<\/h2>\n<pre><code class=\"lang-sql language-sql sql\">CREATE TABLE Studenci (\n    ID INT PRIMARY KEY,\n    Imie VARCHAR(30),\n    Nazwisko VARCHAR(50),\n    RokStudiow INT\n);\n\nCREATE TABLE Kursy (\n    KodKursu VARCHAR(10) PRIMARY KEY,\n    NazwaKursu VARCHAR(100),\n    LiczbaGodzin INT\n);\n\nCREATE TABLE Zakupy (\n    ID INT PRIMARY KEY,\n    Produkt VARCHAR(100),\n    Cena DECIMAL(10, 2),\n    DataZakupu DATE\n);\n\nCREATE TABLE Pracownicy (\n    ID INT PRIMARY KEY,\n    Imie VARCHAR(30),\n    Nazwisko VARCHAR(50),\n    Funkcja VARCHAR(50),\n    DataZatrudnienia DATE\n);<\/code><\/pre>\n<h3>Przykladowe dane<\/h3>\n<pre><code class=\"lang-sql language-sql sql\">INSERT INTO Studenci (ID, Imie, Nazwisko, RokStudiow) VALUES\n(1, &#039;Jan&#039;, &#039;Kowalski&#039;, 1),\n(2, &#039;Anna&#039;, &#039;Nowak&#039;, 2),\n(3, &#039;Piotr&#039;, &#039;Wisniewski&#039;, 3),\n(4, &#039;Maria&#039;, &#039;Zielinska&#039;, 4),\n(5, &#039;Tomasz&#039;, &#039;Lewandowski&#039;, 2),\n(6, &#039;Katarzyna&#039;, &#039;Kowalczyk&#039;, 1),\n(7, &#039;Michal&#039;, &#039;Sikorski&#039;, 3),\n(8, &#039;Ewa&#039;, &#039;Wojcik&#039;, 4),\n(9, &#039;Pawel&#039;, &#039;Mazur&#039;, 2),\n(10, &#039;Agata&#039;, &#039;Dabrowska&#039;, 3);\n\nINSERT INTO Kursy (KodKursu, NazwaKursu, LiczbaGodzin) VALUES\n(&#039;CS101&#039;, &#039;Podstawy programowania&#039;, 30),\n(&#039;CS102&#039;, &#039;Algorytmy i struktury danych&#039;, 40),\n(&#039;CS103&#039;, &#039;Bazy danych&#039;, 35),\n(&#039;CS104&#039;, &#039;Programowanie obiektowe&#039;, 45),\n(&#039;CS105&#039;, &#039;Podstawy sieci komputerowych&#039;, 25),\n(&#039;CS106&#039;, &#039;Systemy operacyjne&#039;, 50),\n(&#039;CS107&#039;, &#039;Inzynieria oprogramowania&#039;, 40),\n(&#039;CS108&#039;, &#039;Bezpieczenstwo komputerowe&#039;, 30),\n(&#039;CS109&#039;, &#039;Programowanie wspolbiezne&#039;, 35),\n(&#039;CS110&#039;, &#039;Zaawansowane techniki programowania&#039;, 45);\n\nINSERT INTO Zakupy (ID, Produkt, Cena, DataZakupu) VALUES\n(1, &#039;Laptop&#039;, 3000.00, &#039;2024-01-15&#039;),\n(2, &#039;Monitor&#039;, 1200.50, &#039;2024-09-15&#039;),\n(3, &#039;Mysz&#039;, 150.00, &#039;2024-02-01&#039;),\n(4, &#039;Klawiatura&#039;, 200.00, &#039;2024-03-01&#039;),\n(5, &#039;Smartphone&#039;, 2500.00, &#039;2024-07-10&#039;),\n(6, &#039;Tablet&#039;, 1500.00, &#039;2024-04-15&#039;),\n(7, &#039;Router&#039;, 350.00, &#039;2024-05-05&#039;),\n(8, &#039;Drukarka&#039;, 600.00, &#039;2024-06-25&#039;),\n(9, &#039;Glosniki&#039;, 250.00, &#039;2024-08-05&#039;),\n(10, &#039;Kamera internetowa&#039;, 450.00, &#039;2024-09-20&#039;);\n\nINSERT INTO Pracownicy (ID, Imie, Nazwisko, Funkcja, DataZatrudnienia) VALUES\n(1, &#039;Jan&#039;, &#039;Kowalski&#039;, &#039;Specjalista&#039;, &#039;2022-01-10&#039;),\n(2, &#039;Anna&#039;, &#039;Nowak&#039;, &#039;Starszy Specjalista&#039;, &#039;2024-02-10&#039;),\n(3, &#039;Piotr&#039;, &#039;Wisniewski&#039;, &#039;Mlodszy Specjalista&#039;, &#039;2023-12-01&#039;),\n(4, &#039;Maria&#039;, &#039;Zielinska&#039;, &#039;Specjalista&#039;, &#039;2021-05-15&#039;),\n(5, &#039;Tomasz&#039;, &#039;Lewandowski&#039;, &#039;Asystent&#039;, &#039;2022-07-20&#039;),\n(6, &#039;Katarzyna&#039;, &#039;Kowalczyk&#039;, &#039;Kierownik&#039;, &#039;2023-03-01&#039;),\n(7, &#039;Michal&#039;, &#039;Sikorski&#039;, &#039;Specjalista&#039;, &#039;2023-11-11&#039;),\n(8, &#039;Ewa&#039;, &#039;Wojcik&#039;, &#039;Asystent&#039;, &#039;2021-06-30&#039;),\n(9, &#039;Pawel&#039;, &#039;Mazur&#039;, &#039;Starszy Specjalista&#039;, &#039;2024-01-15&#039;),\n(10, &#039;Agata&#039;, &#039;Dabrowska&#039;, &#039;Dyrektor&#039;, &#039;2020-09-25&#039;);<\/code><\/pre>\n<hr \/>\n<h2>1. Funkcja COUNT()<\/h2>\n<p>Funkcja <strong>COUNT()<\/strong> zlicza rekordy w tabeli.<\/p>\n<p>Sk\u0142adnia:<\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT COUNT(kolumna) FROM tabela;<\/code><\/pre>\n<ul>\n<li><code>COUNT(kolumna)<\/code> \u2013 liczy tylko warto\u015bci <strong>niepuste (NOT NULL)<\/strong>.<\/li>\n<li><code>COUNT(*)<\/code> \u2013 liczy wszystkie rekordy w tabeli.<\/li>\n<\/ul>\n<p><strong>Przyk\u0142ad:<\/strong><\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT COUNT(ID) FROM Pracownicy;<\/code><\/pre>\n<p>To zapytanie zwr\u00f3ci liczb\u0119 pracownik\u00f3w.<\/p>\n<h3>\u0106wiczenia z COUNT()<\/h3>\n<ul>\n<li>Zlicz wszystkich student\u00f3w w tabeli <em>Studenci<\/em>.<\/li>\n<li>Zlicz kursy, kt\u00f3re maj\u0105 wi\u0119cej ni\u017c 30 godzin.<\/li>\n<li>Zlicz produkty dro\u017csze ni\u017c 1000 z\u0142 w tabeli <em>Zakupy<\/em>.<\/li>\n<li>Zlicz pracownik\u00f3w zatrudnionych po 2023 roku.<\/li>\n<\/ul>\n<hr \/>\n<h2>2. Funkcja SUM()<\/h2>\n<p>Funkcja <strong>SUM()<\/strong> sumuje warto\u015bci liczbowe w kolumnie.<\/p>\n<p>Sk\u0142adnia:<\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT SUM(kolumna) FROM tabela;<\/code><\/pre>\n<p><strong>Przyk\u0142ad:<\/strong><\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT SUM(Cena) FROM Zakupy;<\/code><\/pre>\n<p>To zapytanie poda \u0142\u0105czn\u0105 warto\u015b\u0107 wszystkich zakup\u00f3w.<\/p>\n<h3>\u0106wiczenia z SUM()<\/h3>\n<ul>\n<li>Oblicz \u0142\u0105czn\u0105 liczb\u0119 godzin kurs\u00f3w.<\/li>\n<li>Oblicz ca\u0142kowit\u0105 warto\u015b\u0107 zakup\u00f3w.<\/li>\n<li>Oblicz sum\u0119 godzin kurs\u00f3w, kt\u00f3rych kod zaczyna si\u0119 na <code>CS<\/code>.<\/li>\n<\/ul>\n<hr \/>\n<h2>3. Funkcja AVG()<\/h2>\n<p>Funkcja <strong>AVG()<\/strong> oblicza \u015bredni\u0105 arytmetyczn\u0105.<\/p>\n<p>Sk\u0142adnia:<\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT AVG(kolumna) FROM tabela;<\/code><\/pre>\n<p><strong>Przyk\u0142ad:<\/strong><\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT AVG(LiczbaGodzin) FROM Kursy;<\/code><\/pre>\n<p>To zapytanie zwr\u00f3ci \u015bredni\u0105 liczb\u0119 godzin kurs\u00f3w.<\/p>\n<h3>\u0106wiczenia z AVG()<\/h3>\n<ul>\n<li>Oblicz \u015bredni\u0105 cen\u0119 zakup\u00f3w.<\/li>\n<li>Oblicz \u015bredni\u0105 liczb\u0119 godzin kurs\u00f3w.<\/li>\n<li>(trudne, dla chetnych) Oblicz \u015bredni\u0105 liczb\u0119 lat pracy pracownik\u00f3w.<\/li>\n<li>Oblicz \u015bredni\u0105 cen\u0119 produkt\u00f3w kupionych po <code>2024-01-01<\/code>.<\/li>\n<\/ul>\n<hr \/>\n<h2>4. Funkcje MIN() i MAX()<\/h2>\n<p>Funkcje <strong>MIN()<\/strong> i <strong>MAX()<\/strong> s\u0142u\u017c\u0105 do wyszukiwania najmniejszych i najwi\u0119kszych warto\u015bci.<\/p>\n<p>Sk\u0142adnia:<\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT MIN(kolumna) FROM tabela;\nSELECT MAX(kolumna) FROM tabela;<\/code><\/pre>\n<p><strong>Przyk\u0142ady:<\/strong><\/p>\n<pre><code class=\"lang-sql language-sql sql\">SELECT MIN(Cena) FROM Zakupy;\nSELECT MAX(Cena) FROM Zakupy;<\/code><\/pre>\n<p>To zapytania poka\u017c\u0105 najta\u0144szy i najdro\u017cszy produkt.<\/p>\n<h3>\u0106wiczenia z MIN() i MAX()<\/h3>\n<ul>\n<li>Znajd\u017a najni\u017csz\u0105 liczb\u0119 godzin kursu.<\/li>\n<li>Znajd\u017a najwy\u017csz\u0105 cen\u0119 zakupu.<\/li>\n<li>Znajd\u017a najstarszego pracownika (po dacie zatrudnienia).<\/li>\n<li>Znajd\u017a najm\u0142odszego studenta (po roku studi\u00f3w).<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>Funkcje agreguj\u0105ce pozwalaj\u0105 wykonywa\u0107 operacje na zbiorach danych, a nie tylko na pojedynczych rekordach. Dzi\u0119ki nim mo\u017cemy: podsumowywa\u0107 dane, liczy\u0107 rekordy, oblicza\u0107 warto\u015bci \u015brednie, znajdowa\u0107 minimum i maksimum. S\u0105 one niezb\u0119dne do budowy raport\u00f3w, analiz i zapyta\u0144 statystycznych. W tej lekcji om\u00f3wimy pi\u0119\u0107 najcz\u0119\u015bciej u\u017cywanych funkcji: COUNT() SUM() AVG() MIN() MAX() Dane do cwiczen CREATE [&hellip;]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[63,64,67,68],"tags":[],"class_list":["post-420","post","type-post","status-publish","format-standard","hentry","category-2p","category-3i","category-4i","category-4t"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Funkcje agreguj\u0105ce w MySQL - Tomasz Sadowski<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/zajecia.tsadowski.pl\/index.php\/2026\/09\/22\/funkcje-agregujace-w-mysql-3\/\" \/>\n<meta property=\"og:locale\" content=\"pl_PL\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Funkcje agreguj\u0105ce w MySQL - Tomasz Sadowski\" \/>\n<meta property=\"og:description\" content=\"Funkcje agreguj\u0105ce pozwalaj\u0105 wykonywa\u0107 operacje na zbiorach danych, a nie tylko na pojedynczych rekordach. Dzi\u0119ki nim mo\u017cemy: podsumowywa\u0107 dane, liczy\u0107 rekordy, oblicza\u0107 warto\u015bci \u015brednie, znajdowa\u0107 minimum i maksimum. S\u0105 one niezb\u0119dne do budowy raport\u00f3w, analiz i zapyta\u0144 statystycznych. 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