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SQL> WITH tt AS(
2 SELECT 1 a,2 b FROM dual
3 )SELECT SUM(1) FROM tt;
SUM(1)
----------
1
SQL>
SQL> WITH tt AS(
2 SELECT 1 a,2 b FROM dual UNION ALL
3 SELECT 2 a,2 b FROM dual
4 )SELECT SUM(1) FROM tt;
SUM(1)
----------
2
SQL>
SQL> WITH tt AS(
2 SELECT 1 a,2 b FROM dual UNION ALL
3 SELECT 2 a,2 b FROM dual UNION ALL
4 SELECT 3 a,2 b FROM dual
5 )SELECT SUM(1) FROM tt;
SUM(1)
----------
3