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:
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Last update:
2024-08-28