How to Update Multiple Records in SQL Based on a Single Record Change?

Modifying Multiple Records Based on Single Record Change in SQL

Question:

How to update the positions of multiple records in a table based on the change of a single record's position?

Solution:

To address this issue, a complex query that modifies several records might be required. However, with a simple adjustment to the data structure, we can simplify the process and accomplish it with a single query that modifies only the desired record.

In the provided example, the table contains a "Position" field to order items within a list identified by "ListID." Moving an item (e.g., "Pears" to before "Chips") involves setting its position to the desired position and adjusting the positions of all items in between.

Our goal is to achieve a single query without relying on additional processing or multiple queries.

Subsequently, we can use the following query:

<code class="sql">UPDATE my_table SET position = 15 WHERE listId=1 AND name = 'Pears';</code>

Suppose, in the future, gaps appear between items due to repeated reordering. To resolve this issue, we can periodically execute the following query:

<code class="sql">UPDATE my_table SET position = position * 10;</code>

By multiplying the position values by 10, we introduce sufficient gaps to accommodate future adjustments without losing the ordering information.

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