Firebird Index Creation Fails
Index names need to be unique in the entire database; indexes are not part of table so they need to be uniquely identified. The Interbase 6.0 Language Reference says:


CREATE [UNIQUE] [ASC[ENDING] | DESC[ENDING]] INDEX index ON table (col [, col …]);

  
  ...
  index Unique name for the index


The Firebird Book, 2nd Edition by Helen Borrie says:


  CREATE INDEX &lt;index-name&gt; 
  —names the index. The identifier must be distinct from all other object identifiers in the database, apart from constraint and column identifiers.