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This 3-page SQL Cheat Sheet provides you with the most commonly used SQL statements. Download the SQL cheat sheet, print it out, and stick to your desk.
Whether you need a quick reference for major SQL concepts before an interview, or you want to level-up your existing SQL skills, our SQL cheat sheet is the ideal starting point. Plus, we’ve broken it down into 11 essential SQL topics to help you get the most from this SQL query cheat sheet.
4 wrz 2023 · This cheat sheet is a comprehensive guide to SQL Server, offering a quick reference to its essential commands. It covers the basics of creating and displaying databases and tables, the commands to modify tables, and the fundamental syntax for T-SQL commands such as SELECT, INSERT, UPDATE, and DELETE.
What is the difference between MySQL unique and non-unique index in terms of performance? Let us say I want to make an index on a combo of 2 columns, and the combination is unique, but I create a non-unique index.
5 sty 2024 · In MySQL, a unique index is a crucial tool for ensuring that values in a specific column or a group of columns within a table are unique. This feature is essential to maintain data integrity by preventing duplicate entries where uniqueness is required.
The following SQL creates an index named "uidx_pid" on the "PersonID" column in the "Persons" table: CREATE UNIQUE INDEX uidx_pid. ON Persons (PersonID); Note: The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.
SELECT DISTINCT c1 FROM t. WHERE condition; Query distinct rows from a table. SELECT c1, c2 FROM t. ORDER BY c1 ASC [DESC]; Sort the result set in ascending or descending order. SELECT c1, c2 FROM t ORDER BY c1. LIMIT n OFFSET offset; Skip offset of rows and return the next n rows. SELECT c1, aggregate(c2) FROM t GROUP BY c1;
