How to Show/Hide Products Based on Manufacturer Rules in MySQL Using Conditional SELECT Statements?

MySQL Select Statement with Conditional Visibility Query

In scenarios where table data requires conditional display based on specific criteria, it is common to employ conditional statements, such as CASE or IF/ELSEIF, within a MySQL select query. In this instance, a query is needed that determines product visibility based on manufacturer rules.

Problem:

Given two tables, one containing manufacturer information and regions of visibility, and another containing product information, the objective is to create a query that returns product details along with a computed value indicating where the product can be viewed. The computed value should be based on whether the product is new or used, and the expose rules defined in the manufacturer table.

Solution:

Both CASE and IF/ELSEIF statements can be utilized to achieve this result, with CASE expressing conditions more succinctly.

The following query uses a CASE statement:

SELECT 
  t2.company_name,
  t2.expose_new,
  t2.expose_used,
  t1.title,
  t1.seller,
  t1.status,
  CASE status
      WHEN 'New' THEN t2.expose_new
      WHEN 'Used' THEN t2.expose_used
      ELSE NULL
  END as 'expose'
FROM
  `products` t1
JOIN manufacturers t2
  ON
    t2.id = t1.seller
WHERE
  t1.seller = 4238

In this query:

• The CASE statement evaluates the status field of each product.
• Based on the status ('New' or 'Used'), it retrieves the corresponding expose_new or expose_used value from the manufacturers table.
• The result is assigned to the 'expose' column, which indicates the visibility of the product.

This query dynamically determines the visibility constraints for each product based on the manufacturer's settings and the product's status. It provides the necessary information for conditional display or distribution based on the specified regions.

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