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The SQL Workshop

You're reading from   The SQL Workshop Learn to create, manipulate and secure data and manage relational databases with SQL

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Product type Paperback
Published in Dec 2019
Publisher Packt
ISBN-13 9781838642358
Length 288 pages
Edition 1st Edition
Languages
Concepts
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Authors (3):
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Prashanth Jayaram Prashanth Jayaram
Author Profile Icon Prashanth Jayaram
Prashanth Jayaram
Frank Solomon Frank Solomon
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Frank Solomon
Awni Al Saqqa Awni Al Saqqa
Author Profile Icon Awni Al Saqqa
Awni Al Saqqa
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Toc

Table of Contents (13) Chapters Close

Preface 1. SQL Basics FREE CHAPTER 2. Manipulating Data 3. Normalization 4. The SELECT Statement 5. Shaping Data with the WHERE Clause 6. JOINS 7. Subqueries, Cases, and Views 8. SQL Programming 9. Security 10. Aggregate Functions 11. Advanced SQL Appendix

The DELETE Operation

The DELETE statement deletes one or more rows within a table. Like the INSERT operations, DELETE also works only on a single table at a time. A deletion operation should be performed very carefully because deletion is permanent. Many database tools require you to add a WHERE clause to the DELETE FROM statement. When performing these deletion operations, which require a WHERE clause, and you would like to delete all the rows in a table, you could work around this by using a condition that is true for all the rows in the table.

For example, say you have an employee with empno 1234 who is no longer associated with the company. In such cases your query would look like the following:

DELETE FROM employees
    WHERE empno = 1234;

If you would like to remove the top 5 rows from the employees table, we would use the following query:

DELETE FROM employees
    LIMIT 5;

Exercise 2.03: Deleting a record from a table

...
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