Sql queries

1. Query to fetch links of a particular user  
   • To fetch all categories and number of links in the category for a particular user :
     • SELECT l.`categoryId` as `Category Id`,lc.title as `Category Name`,count(*) as `Number of links` FROM `save-app`.`links` l inner join
       `link-categories` lc on lc.`key` = l.categoryId
       where l.createdBy = <user-id-of-the-user>
       group by categoryId
   • To fetch all the thumbnail text for a particular category:
     • select l.title as `Link Title`,categoryId as `Category ID`,lc.title as `Category Name` from `links` l
       inner join `link-categories` lc on lc.`key`= l.categoryId
       where l.createdBy = 12
       order by l.categoryId
2. Query to fetch total number of referrals done by users
   • SELECT R.userId as `User Id`,U.referalCode as `Referral Code`,count(*) as `Total Referrals`
     FROM `referred-users` R, users U
     where R.userId = U.key group by R.userId
3. Query to see all different types of logins
   • SELECT provider as `Login Type`,count(*) as `Number of logins` FROM `save-app`.users
     group by provider
4. Query to see images with and without thumbnail
   • To see all links with and without images 
     • SELECT link,title,
       CASE WHEN image IS NOT NULL THEN 'Image Found'
       ELSE 'Image Not Found'
       END AS image
       FROM links;
   • To see total number of links with and without images
     • SELECT CASE WHEN image IS NOT NULL THEN 'With Image'
       ELSE 'Without Image'
       END AS `Link Type`,
       COUNT(*) AS `Number of Links`
       FROM links
       GROUP BY CASE WHEN image IS NOT NULL THEN 'With Image'
       ELSE 'Without Image'
       END;
   • To see total number of links with and without images based on category
     • select lc.`key` as `Category ID`,lc.title as `Categories Without Image`,count(*) as `Number of Links`
       from `link-categories` lc,links l
       where l.image is null and
       l.categoryId = lc.`key`
       group by l.categoryId