How to use variables column name in where clause MySQL?-CodePudding

In this query:

SELECT *
FROM general_settings AS general_settings
JOIN settings_attribute AS settings_attribute ON settings_attribute.id = general_settings.settings_attribute_id 
JOIN user_settings AS user_settings ON general_settings.user_settings_id = user_settings.id 
WHERE 
(settings_attribute.name = 'AAA' AND brand_settings.AAA <> general_settings.value)
OR
(settings_attribute.name = 'BBB' AND brand_settings.BBB <> general_settings.value)
OR
(settings_attribute.name = 'CCC' AND brand_settings.CCC <> general_settings.value)
;

I want a way using MySQL or Redshift to use settings_attribute.name as column name to avoid writing all the attribute names as a static in the query, for example like this:

SELECT *
FROM general_settings AS general_settings
JOIN settings_attribute AS settings_attribute ON settings_attribute.id = general_settings.settings_attribute_id 
JOIN user_settings AS user_settings ON general_settings.user_settings_id = user_settings.id 
WHERE 
brand_settings.@settings_attribute.name <> general_settings.value
;

CodePudding user response：

No, this is not possible. In SQL, all identifiers (e.g. column names) must be explicit and fixed in the query at the time it is parsed, so the SQL engine can verify that the columns actually exist before it begins executing. It's not possible for a query to name different columns based on the string values it reads during execution.

What would happen if your settings_attribute.name contained 'XYZ' in some row, but there was no column by that name? It would be an error if you named a column that didn't exist, but in SQL that is checked at the time the query is parsed.