After an upgrade and database migration, old theme is not being replaced by new theme

Issue

• After an upgrade, a new theme developed to replace an old theme is not applied to pages that utilized the old theme.
• There are multiple pages with different theme settings and updating them one-by-one is impractical. 

Environment

• DXP 7.4
  

Resolution

Using the following SQL Statements, you could apply a new theme and replace an old theme, in the pages that use it: 

update <databaseName>.Layout set themeId = 'newcompanytheme_WAR_newcompanytheme' where themeId = 'oldcompanytheme_WAR_OldCompanyTheme';
update <databaseName>.LayoutSet set themeId = 'newcompanytheme_WAR_newcompanytheme' where themeId = 'oldcompanytheme_WAR_OldCompanyTheme';