How to Efficiently Deduct a Value from a MySQL Column?

Modifying a Column by Deducting a Value

When working with MySQL databases, users may encounter the need to update a specific column by subtracting a predetermined value. This can be achieved through a well-crafted query, as demonstrated below:

Query:

UPDATE a75ting.username
SET points = points - 5

Explanation:

The above query targets the a75ting database and username table. It specifically modifies the points column by decrementing its current value by 5.

Error Correction:

Initially, the user attempted to execute the following query:

UPDATE `a75ting`.`username` SET `points` = '`points` - 5'

However, this query would fail because enclosing the subtraction expression within single quotes converts it into a plaintext string. As a result, MySQL interprets "points - 5" as a literal value rather than a mathematical operation.

Correct Syntax:

To perform the intended subtraction, the single quotes must be omitted. This allows MySQL to recognize points as a field and execute the subtraction operation accordingly.

Note:

This query assumes that the points column is of a numerical data type, such as INT or FLOAT. Attempting to subtract a value from a non-numerical field will result in an error.

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