SQL Basics

Table of contents

1. 1. A little bit on databases

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   Find out what relational databases are and get to know SQL – a language to talk to databases.

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   1. Introduction
      1. Relational databases
      2. Tables
      3. Columns and rows
      4. Notation
      5. SQL
      6. Queries

2. 2. Selecting from one table

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   Discover how to select data from a single table.

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   1. See the whole table
      1. Get all data
      2. Read the result
   2. Select some columns
      1. Select one column
      2. Select many columns
   3. Filtering rows
      1. Select only a few rows
      2. Conditional operators
      3. The not equal sign (!=)
      4. Conditional operators and selecting columns
   4. Logic
      1. Logical operators – OR
      2. Logical operators – AND
      3. The BETWEEN operator
      4. Logical operators – NOT
      5. Join even more conditions
   5. Text patterns
      1. Use text
      2. The percentage sign (%)
      3. The percentage sign (%) continued
      4. The underscore sign (_)
   6. To be or NULL to be
      1. Looking for NOT NULL values
      2. Looking for NULL values
      3. Comparisons with NULL
   7. A little bit of mathematics
      1. Basic mathematical operators
   8. Let's practice
      1. Put your skills into practice

3. 3. Querying more than one table

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   Learn how to select data from multiple tables.

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   1. How to query more than one table
      1. Data from multiple tables
      2. Get to know the tables
      3. Multiple tables in the clause FROM
      4. Join tables on a condition
   2. Creating JOINs
      1. The keyword JOIN
      2. Join tables using JOIN
   3. Referencing columns
      1. Display specific columns
      2. Refer to columns without table names
      3. Rename columns with AS
      4. Filter the joined tables
      5. Filter the joined tables continued
   4. Let's practice
      1. Put your skills into practice
      2. Further practice

4. 4. Aggregation and grouping

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   Computations in SQL? Why not? You will learn how to group rows and compute statistics with aggregate functions.

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   1. Ordering
      1. The scope of the course part
      2. Get to know the tables
      3. Sort the rows – ORDER BY
      4. ORDER BY with conditions
      5. Ascending and descending orders
      6. Sort by a few columns
   2. Eliminating duplicate results
      1. Duplicate results
      2. Select distinctive values
      3. Select distinctive values in certain columns
   3. Aggregation
      1. Count the rows
      2. Count the rows, ignore the NULLS
      3. Count distinctive values in a column
      4. Find the minimum and maximum value
      5. Find the average value
      6. Find the sum
   4. Grouping
      1. Group the rows and count them
      2. Find min and max values in groups
      3. Find the average value in groups
      4. Group by a few columns
   5. HAVING: filtering and ordering groups
      1. Filter groups
      2. Filter groups continued
      3. Order groups
   6. Let's practice
      1. Put your skills into practice

5. 5. More on JOINs

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   Learn about various kinds of JOINs to best suit your needs.

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   1. Get to know the data
      1. The scope of the course part
      2. Get to know the table room
      3. Get to know the table student
      4. Get to know the table student – continued
      5. Get to know the table equipment
      6. Get to know the table equipment – continued
   2. JOIN revisited
      1. JOIN revised
      2. JOIN columns revised
      3. INNER JOIN
      4. How INNER JOIN works
   3. LEFT JOIN
      1. LEFT JOIN explained
      2. LEFT JOIN again
   4. RIGHT JOIN
      1. RIGHT JOIN explained
      2. RIGHT JOIN again
   5. FULL JOIN
      1. FULL JOIN explained
   6. OUTER JOINS
      1. The keyword OUTER
   7. NATURAL JOIN
      1. NATURAL JOIN
      2. NATURAL JOIN explained
   8. Aliases for tables
      1. Table aliases
      2. Aliases in self-joins
      3. Joining more tables
      4. Summary

6. 6. Subqueries

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   Queries within queries? That's right! Discover how to build and use subqueries.

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   1. Introduction
      1. The scope of the course part
      2. Get to know the data – table country
      3. Get to know the data – tables city and mountain
      4. Get to know the data – tables trip and hiking_trip
   2. Very simple subqueries
      1. Get to know subqueries
      2. Subqueries with various logical operators
      3. Subqueries with functions
   3. Subqueries with multiple results
      1. The operator IN
      2. The operator IN with subqueries
      3. The operator ALL
      4. The operator ANY
   4. Correlated subqueries
      1. Get to know correlated queries
      2. Aliases for tables
      3. The operator IN with correlated subqueries
      4. The operator EXISTS
      5. The operator EXISTS with NOT
      6. The operator ALL in correlated subqueries
      7. The operator ANY in correlated subqueries
   5. Other subqueries
      1. Subqueries in the FROM clause
      2. Subqueries in the FROM clause
      3. Subqueries in the SELECT clause
      4. Subqueries – summary

7. 7. Set operations

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   Combine query results using set operations like UNION, INTERSECT or MINUS.

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   1. Introduction
      1. The scope of the course part
      2. Get to know the tables
      3. Get to know the tables – cycling medalists
      4. Get to know the tables continued
      5. Get to know the tables – speed skating medalists
   2. UNION
      1. How UNION works
      2. Conditions for UNION
      3. The keyword UNION ALL
   3. INTERSECT
      1. How INTERSECT works
   4. EXCEPT
      1. How EXCEPT works
      2. MINUS instead of EXCEPT
      3. Summary

8. 8. Quiz

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   Check your SQL skills.

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   1. Quiz
      1. Introduction
      2. Task 1 – Selecting rows from one table
      3. Task 2 – Selecting rows from multiple tables
      4. Task 3 – Aggregation and grouping
      5. Task 4 – Sophisticated JOINs
      6. Task 5 – Subqueries
      7. Task 6 – Set operations
      8. Task 7 – Challenge
      9. Congratulations

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