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SQL Handwritten Notes Repository: A collection of PDF notes covering SQL concepts with concise definitions and examples. Explore fundamental commands, date/time functions, joins, and more. Contributions welcome!
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SQL is a language to query data. In most cases it is used to retrieve data from databases. Because SQL is so convenient, it may be used to query data that lives outside of databases (for example, you can use it with plain files). In day-to-day work of Data Engineers it plays a very important role.
1 cze 2021 · Use the || operator to concatenate two strings: SELECT 'Hi ' || 'there!'; -- result: Hi there! ||. Use this trick for numbers: Some databases implement non-standard solutions for concatenating strings like CONCAT() or CONCAT_WS(). Check the documentation for your specific database. Use the _ character to replace any single character.
2 wrz 2024 · In this guide, we will see a comprehensive cheat sheet for essential SQL operations, offering a practical reference for tasks ranging from database creation to advanced data handling techniques.
Chapter 1: Getting started with SQL; Chapter 2: ALTER TABLE; Chapter 3: AND & OR Operators; Chapter 4: Cascading Delete; Chapter 5: CASE; Chapter 6: Clean Code in SQL; Chapter 7: Comments; Chapter 8: Common Table Expressions; Chapter 9: CREATE Database; Chapter 10: CREATE FUNCTION; Chapter 11: CREATE TABLE; Chapter 12: cross apply, outer apply ...
1 cze 2021 · Fetch all names that start with any letter followed by 'atherine': SELECT name FROM names WHERE name LIKE '_atherine'; Fetch all names that end with 'a': SELECT name FROM names WHERE name LIKE '%a'; USEFUL FUNCTIONS. Get the count of characters in a string: SELECT LENGTH('LearnSQL.com');-- result: 12 Convert all letters to lowercase: SELECT ...
