Your message has been sent to W3Schools.
W3Schools is optimized for learning, testing, and training. Examples might be simplified to improve reading and basic understanding.
Welcome to SQL (video) | SQL basics | Khan Academy
All Rights Reserved. Catch up here.
How can Crate. About CrateDB Free trial Smart Factory Data Platform Turn-key, full-stack solution enables real-time, data-driven manufacturing for discrete manufacturers in consumer packaged goods. Use Cases.
Smart Factories Monitor streams of factory sensor data to optimize output, efficiency, control, safety. Smart IT Analyze metrics and logs to monitor security, compliance, usage, or billing. Smart Vehicles Track vehicle locations and system status to improve fleet safety and efficiency. Put machine data to work.
Simply put, an index is a pointer to data in a table. An index in a database is very similar to an index in the back of a book. For example, if you want to reference all pages in a book that discusses a certain topic, you first refer to the index, which lists all the topics alphabetically and are then referred to one or more specific page numbers.
Welcome to SQL
Indexes can be created or dropped with no effect on the data. Creating an index involves the CREATE INDEX statement, which allows you to name the index, to specify the table and which column or columns to index, and to indicate whether the index is in an ascending or descending order.
- Relational databases and SQL;
- Geriatric Care, Third Edition (Fergusons Careers in Focus).
- Accelerate and automate your analytics?
Indexes can also be unique, like the UNIQUE constraint, in that the index prevents duplicate entries in the column or combination of columns on which there is an index. Unique indexes are used not only for performance, but also for data integrity. A unique index does not allow any duplicate values to be inserted into the table.