---- UNION (also INTERSECT, EXCEPT)---- Simple UNION constructsSELECT 1 AS two UNION SELECT 2;SELECT 1 AS one UNION SELECT 1;SELECT 1 AS two UNION ALL SELECT 2;SELECT 1 AS two UNION ALL SELECT 1;SELECT 1 AS three UNION SELECT 2 UNION SELECT 3;SELECT 1 AS two UNION SELECT 2 UNION SELECT 2;SELECT 1 AS three UNION SELECT 2 UNION ALL SELECT 2;SELECT 1.1 AS two UNION SELECT 2.2;-- Mixed typesSELECT 1.1 AS two UNION SELECT 2;SELECT 1 AS two UNION SELECT 2.2;SELECT 1 AS one UNION SELECT 1.0::float8;SELECT 1.1 AS two UNION ALL SELECT 2;SELECT 1.0::float8 AS two UNION ALL SELECT 1;SELECT 1.1 AS three UNION SELECT 2 UNION SELECT 3;SELECT 1.1::float8 AS two UNION SELECT 2 UNION SELECT 2.0::float8;SELECT 1.1 AS three UNION SELECT 2 UNION ALL SELECT 2;SELECT 1.1 AS two UNION (SELECT 2 UNION ALL SELECT 2);---- Try testing from tables...--SELECT f1 AS five FROM FLOAT8_TBLUNIONSELECT f1 FROM FLOAT8_TBL;SELECT f1 AS ten FROM FLOAT8_TBLUNION ALLSELECT f1 FROM FLOAT8_TBL;SELECT f1 AS nine FROM FLOAT8_TBLUNIONSELECT f1 FROM INT4_TBL;SELECT f1 AS ten FROM FLOAT8_TBLUNION ALLSELECT f1 FROM INT4_TBL;SELECT f1 AS five FROM FLOAT8_TBL  WHERE f1 BETWEEN -1e6 AND 1e6UNIONSELECT f1 FROM INT4_TBL  WHERE f1 BETWEEN 0 AND 1000000;SELECT CAST(f1 AS char(4)) AS three FROM VARCHAR_TBLUNIONSELECT f1 FROM CHAR_TBL;SELECT f1 AS three FROM VARCHAR_TBLUNIONSELECT CAST(f1 AS varchar) FROM CHAR_TBL;SELECT f1 AS eight FROM VARCHAR_TBLUNION ALLSELECT f1 FROM CHAR_TBL;SELECT f1 AS five FROM TEXT_TBLUNIONSELECT f1 FROM VARCHAR_TBLUNIONSELECT TRIM(TRAILING FROM f1) FROM CHAR_TBL;---- INTERSECT and EXCEPT--SELECT q2 FROM int8_tbl INTERSECT SELECT q1 FROM int8_tbl;SELECT q2 FROM int8_tbl INTERSECT ALL SELECT q1 FROM int8_tbl;SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl;SELECT q2 FROM int8_tbl EXCEPT ALL SELECT q1 FROM int8_tbl;SELECT q2 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q1 FROM int8_tbl;SELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl;SELECT q1 FROM int8_tbl EXCEPT ALL SELECT q2 FROM int8_tbl;SELECT q1 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q2 FROM int8_tbl;---- Mixed types--SELECT f1 FROM float8_tbl INTERSECT SELECT f1 FROM int4_tbl;SELECT f1 FROM float8_tbl EXCEPT SELECT f1 FROM int4_tbl;---- Operator precedence and (((((extra))))) parentheses--SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl;SELECT q1 FROM int8_tbl INTERSECT (((SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl)));(((SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl))) UNION ALL SELECT q2 FROM int8_tbl;SELECT q1 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl;SELECT q1 FROM int8_tbl UNION ALL (((SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl)));(((SELECT q1 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl))) EXCEPT SELECT q1 FROM int8_tbl;---- Subqueries with ORDER BY & LIMIT clauses---- In this syntax, ORDER BY/LIMIT apply to the result of the EXCEPTSELECT q1,q2 FROM int8_tbl EXCEPT SELECT q2,q1 FROM int8_tblORDER BY q2,q1;-- This should fail, because q2 isn't a name of an EXCEPT output columnSELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1;-- But this should work:SELECT q1 FROM int8_tbl EXCEPT (((SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1)));---- New syntaxes (7.1) permit new tests--(((((select * from int8_tbl)))));