The following SELECT statements are syntactically correct in Teradata SQL. The first statement does not reference any tables, so a FROM clause is unnecessary. This syntax is a Teradata extension to the ANSI SQL:2011 standard.
SELECT DATE, TIME; SELECT x1,x2 FROM t1,t2 WHERE t1.x1=t2.x2;
SELECT x1 FROM t1 WHERE x1 IN (SELECT x2 FROM t2);