There should be two tags:
columnar-store for MariaDB and friends - see a list here. This tag should be for systems which specifically store classic RDBMS tables but with the values stored column-by-column and not row-by-row. Otherwise, the syntax would be unchanged and classic SQL should be [ an | the ] access method (of choice). This is my understanding of how the MariaDB columnar store works.
SQL is the most proven way of processing data. So, MariaDB ColumnStore
is compatible with standard SQL using the MariaDB interface. Full SQL
compliance means MariaDB ColumnStore works out-of-the-box with your
existing business intelligence tools and SQL queries.
column-family (or possibly
wide-column) for Cassandra and friends - see a list here. From here:
Unlike a table in an RDBMS, different rows in the same column family
do not have to share the same set of columns, and a column may be
added to one or multiple rows at any time.
column-family databases are more typically distributed and have alternatives to SQL (which may or may not look similar), but are more NoSQL systems than classic RDBMS's.
Unfortunately, there is an element of overlap (and/or confusion) over the exact demarcation line between these two types of system - this site (formerly NoSQL-Database.org) lists some systems as "column family" which are shown as "columnar" stores on the wiki page referenced above.
My personal opinion is that we should create the two tags above (with usage guidance) and the extant
columnstore tag (no usage guidance and only 126 questions) should be retired - with possibly
wide-family as a synonym.
With respect to the SQL Server aspect, it's not my gig so I'll leave that to others to suggest suitable tags for its functionality. However, having quickly searched, I think that the
columnstore-index tag should be reserved for the SQL Server functionality - but SQL Server guys may want to chip in on this?