From aef8bfe76eb6236929ddfef19d4b7d41ff91e9c6 Mon Sep 17 00:00:00 2001
From: Tomas Krejci <tk@tomaskrejci.com>
Date: Mon, 8 Jun 2026 17:01:47 +0200
Subject: [PATCH] Add second lecture SQL examples

---
 Lecture_1/01-select.sql              | 48 +++++++++++++++++++++
 lecture_2/01-definicni-prikazy.sql   | 42 ++++++++++++++++++
 lecture_2/02-manipulacni-prikazy.sql | 64 ++++++++++++++++++++++++++++
 3 files changed, 154 insertions(+)
 create mode 100644 lecture_2/01-definicni-prikazy.sql
 create mode 100644 lecture_2/02-manipulacni-prikazy.sql

diff --git a/Lecture_1/01-select.sql b/Lecture_1/01-select.sql
index 1505411..726ad2e 100644
--- a/Lecture_1/01-select.sql
+++ b/Lecture_1/01-select.sql
@@ -30,4 +30,52 @@ SELECT * FROM accounts WHERE currency NOT IN ('CZK', 'USD');
 
 SELECT * FROM clients WHERE email IS NULL;
 
+SELECT * FROM clients WHERE email IS NOT NULL;
+
 SELECT * FROM clients WHERE name LIKE 'Ja%';
+
+-- Use ILIKE for a case-insensitive pattern match.
+SELECT * FROM clients WHERE name ILIKE 'JA%';
+
+-- Sort accounts by balance in ascending or descending order.
+SELECT * FROM accounts ORDER BY balance;
+
+SELECT * FROM accounts ORDER BY balance DESC;
+
+-- Apply secondary sorting when currency values are equal.
+SELECT * FROM accounts ORDER BY currency DESC, balance ASC;
+
+-- Limit the number of returned records.
+SELECT * FROM accounts ORDER BY currency DESC, balance ASC LIMIT 5;
+
+-- Skip records before returning the limited result set.
+SELECT *
+FROM accounts
+ORDER BY currency DESC, balance ASC
+LIMIT 5
+OFFSET
+    2;
+
+-- Return distinct currency values without duplicates.
+SELECT DISTINCT (currency) FROM accounts;
+
+SELECT * FROM cards;
+
+-- Return cards with their associated clients.
+SELECT * FROM cards JOIN clients ON cards.client_id = clients.id;
+
+-- Select only the required columns from joined tables.
+SELECT clients.name, cards.card_number
+FROM cards
+    JOIN clients ON cards.client_id = clients.id;
+
+-- Use aliases to distinguish similarly named columns.
+SELECT clients.id AS client_id, cards.id AS card_id
+FROM cards
+    JOIN clients ON cards.client_id = clients.id;
+
+SELECT * FROM accounts JOIN cards ON accounts.id = cards.account_id;
+
+SELECT * FROM accounts LEFT JOIN cards ON accounts.id = cards.account_id;
+
+-- PostgreSQL console command for describing the accounts table: \d accounts
diff --git a/lecture_2/01-definicni-prikazy.sql b/lecture_2/01-definicni-prikazy.sql
new file mode 100644
index 0000000..d2f2471
--- /dev/null
+++ b/lecture_2/01-definicni-prikazy.sql
@@ -0,0 +1,42 @@
+-- Display the name of the current database.
+
+SELECT CURRENT_DATABASE();
+
+-- Create tables starting with entities that do not depend on foreign keys.
+
+CREATE TABLE enclosures (
+    id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    name VARCHAR(255) NOT NULL,
+    area INTEGER,
+    biome VARCHAR(20)
+);
+
+-- Delete a table.
+DROP TABLE enclosures;
+
+CREATE TABLE keepers (
+    id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    name VARCHAR NOT NULL,
+    salary NUMERIC(10, 3)
+);
+
+CREATE TABLE animals (
+    id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    enclosure_id INT,
+    name VARCHAR NOT NULL,
+    is_healthy BOOLEAN DEFAULT TRUE,
+    adoption_date DATE,
+    note TEXT,
+    FOREIGN KEY (enclosure_id) REFERENCES enclosures (id)
+);
+
+-- Junction table for the many-to-many relationship.
+CREATE TABLE animals_keepers (
+    animal_id INT NOT NULL,
+    keeper_id INT NOT NULL,
+    PRIMARY KEY (animal_id, keeper_id),
+    FOREIGN KEY (animal_id) REFERENCES animals (id),
+    FOREIGN KEY (keeper_id) REFERENCES keepers (id)
+);
+
+-- Change an existing table structure with ALTER TABLE.
diff --git a/lecture_2/02-manipulacni-prikazy.sql b/lecture_2/02-manipulacni-prikazy.sql
new file mode 100644
index 0000000..79fd05b
--- /dev/null
+++ b/lecture_2/02-manipulacni-prikazy.sql
@@ -0,0 +1,64 @@
+-- Use INSERT to add a record.
+INSERT INTO
+    enclosures (biome, name, area)
+VALUES (
+        'Arktida',
+        'Ledové království',
+        2500
+    );
+
+SELECT * FROM enclosures;
+
+INSERT INTO
+    enclosures (name, area, biome)
+VALUES (
+        'Savanvoá pláň',
+        1700,
+        'Savana'
+    ),
+    (
+        'Křišťálová laguna',
+        900,
+        'Tropické vody'
+    ),
+    (
+        'Zelený divoký les',
+        750,
+        'Mírný les'
+    );
+
+-- Increase every enclosure area by 100 square meters.
+UPDATE enclosures SET area = area + 100;
+
+SELECT * FROM enclosures;
+
+-- Increase smaller enclosure areas by 50 square meters.
+
+UPDATE enclosures SET area = area + 50 WHERE area < 1500;
+
+-- Update multiple columns in one statement.
+UPDATE enclosures SET biome = 'Oceán', area = area + 25 WHERE id = 3;
+
+-- Delete a selected record.
+
+DELETE FROM enclosures WHERE id = 3;
+
+SELECT * FROM enclosures;
+
+INSERT INTO
+    animals (name, adoption_date, note)
+VALUES (
+        'hroch',
+        '2026-10-25',
+        'hrošík Igor'
+    );
+
+INSERT INTO
+    animals (name, adoption_date, note)
+VALUES ('vlk', NOW(), 'pozor kouše');
+
+INSERT INTO
+    animals (name, adoption_date, note)
+VALUES ('vlk', NOW(), 'pozor kouše');
+
+SELECT * FROM animals;