pepijnve commented on code in PR #25112:
URL: https://github.com/apache/datafusion/pull/25112#discussion_r4082170169


##########
docs/source/user-guide/sql/ddl.md:
##########
@@ -35,6 +35,58 @@ CREATE DATABASE [ IF NOT EXISTS ] <i><b>catalog</i></b>
 CREATE DATABASE cat;
 ```
 
+## CREATE EXTERNAL CATALOG

Review Comment:
   I should have taken a closer look at the existing documentation. My bad.
   
   The usage of this terminology is kind of inconsistent across the RDBMS 
ecosystem. The SQL spec talks about a hierarchy of catalogs, schemas, and 
schema objects (tables, views, etc.). What 'database' maps to seems to be 
implementation dependent. In 
[Databricks](https://docs.databricks.com/aws/en/sql/language-manual/sql-ref-syntax-ddl-create-database)
 and [MySQL](https://dev.mysql.com/doc/refman/8.4/en/create-database.html) for 
instance, `CREATE DATABASE` is a synonym for `CREATE SCHEMA`.
   
   The term catalog on the other hand maps quite nicely to [Iceberg 
catalogs](https://iceberg.apache.org/terms/#catalog) and [many 
others](https://docs.starrocks.io/docs/data_source/catalog/) (thank you for the 
list StarRocks). Looking at Iceberg, a database/schema maps to a namespace 
there.
   
   But... DataFusion today treats `CREATE DATABASE` as a synonym for `CREATE 
CATALOG`. Not sure how best to proceed.



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