When DO You Use a Semicolon?

I'm passing Oracle statements to an Oracle server via an Access app using Access pass through queries. In constructing the appropriate SQL, I've been tacking a semicolon at the end. For example:

SELECT FB_BLDG_NAME "Building", FD_NAME "Facility", FB_PK FROM TMA.F_FACILITIES, TMA.F_BUILDINGS WHERE FD_PK = FB_FD_FK UNION Select
'<Any Building>', '<Any Facility>', 0 from TMA.F_BUILDINGS ORDER BY 2,1;

However, when constructing something similar to the above, but with a case expression, I kept getting ORA-00911: invalid character. When I dropped the semicolon and passed the statement as below:

SELECT GRP_TAG_NO || ' ' || GRP_DESCRIPTION "Group", CASE WHEN GRP_TYPE = 'R' THEN 'Area' WHEN GRP_TYPE = 'E' THEN 'Equipment' WHEN GRP_TYPE =
'T' THEN 'Tool' WHEN GRP_TYPE = 'A' THEN 'Asset' WHEN GRP_TYPE = 'V'
THEN 'Vehicle' ELSE '<Any>' END "Type", GRP_PK FROM TMA.F_GROUPS UNION SELECT '<Any>', '<Any>', 0 FROM TMA.F_GROUPS ORDER BY 1

Why does this occur, and when should I use the semicolon? Oracle server is version 8.1.7.4.0.

Thanks very much in advance for any help on this.

-- 
Tim - http://www.ucs.mun.ca/~tmarshal/
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