UPDATE statement

Purpose of the UPDATE Statement

The UPDATE statement modifies existing records in a table. It allows developers to change the values of one or more columns in a specific row or set of rows based on certain conditions.

Advantages and Disadvantages of Using the UPDATE Statement:

Trade-offs	Description
Advantages	- Allows for updating existing data without the need to delete and re-insert records.
	- Provides flexibility in modifying specific columns or rows based on specified conditions.
	- Can be used in conjunction with WHERE clause to update only selected rows, reducing unnecessary updates and improving performance.
	- Supports bulk updates, allowing multiple rows to be modified in a single statement.
Disadvantages	- Incorrectly formulated UPDATE statements can lead to unintended data changes or data loss.
	- Lack of proper WHERE clause can result in updating all rows in a table, potentially causing data corruption or performance issues.
	- May cause locking and contention issues in high-concurrency environments, impacting the performance of other queries accessing the same table.

Syntax of an UPDATE Statement:

Option	Description
UPDATE table_name	This clause specifies the name of the table you want to modify.
SET column_name1 = value1, column_name2 = value2, ...	This clause defines which columns you want to update and their corresponding new values. You can update multiple columns by separating them with commas.
WHERE condition (optional)	This clause specifies a condition that filters which rows in the table will be affected by the update. If omitted, all rows in the table will be updated.

UPDATE table_name
SET column1 = value1, column2 = value2, ...
[WHERE condition];

In this example, the statement does the following:

• Modifies the salary column for employees in the ‘Sales’ department.

• Increases the salary of each employee by 10% (salary * 1.1).

UPDATE employees
SET salary = salary * 1.1
WHERE department = 'Sales';

Fundamental SQL links:

• Common SQL
• SQL Basics
• SELECT
• INSERT
• DELETE
• SQL Operators

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Last update: 2024-10-30