In a multi-statement request, the semicolons that begin the line are used only to separate the statements. BTEQ does not submit any of the statements to SQL Engine until it encounters a semicolon as the last nonspace character of a line. At that time, BTEQ sends all statements for processing as one single request.
Do not use an ANSI comment statement in conjunction with a semicolon character to indicate the final statement of a multi-statement request. If the semicolon appears after an ANSI comment, it is treated as part of the comment text string. If it appears before an ANSI comment, it does not qualify as the last nonspace character on the line.
For complete documentation on Teradata SQL, see Teradata Vantage™ - SQL Fundamentals, B035-1141.