-- -- UNION (also INTERSECT, EXCEPT) -- -- Simple UNION constructs SELECT 1 AS two UNION SELECT 2; two ----- 1 2 (2 rows) SELECT 1 AS one UNION SELECT 1; one ----- 1 (1 row) SELECT 1 AS two UNION ALL SELECT 2; two ----- 1 2 (2 rows) SELECT 1 AS two UNION ALL SELECT 1; two ----- 1 1 (2 rows) SELECT 1 AS three UNION SELECT 2 UNION SELECT 3; three ------- 1 2 3 (3 rows) SELECT 1 AS two UNION SELECT 2 UNION SELECT 2; two ----- 1 2 (2 rows) SELECT 1 AS three UNION SELECT 2 UNION ALL SELECT 2; three ------- 1 2 2 (3 rows) SELECT 1.1 AS two UNION SELECT 2.2; two ----- 1.1 2.2 (2 rows) -- Mixed types SELECT 1.1 AS two UNION SELECT 2; two ----- 1.1 2 (2 rows) SELECT 1 AS two UNION SELECT 2.2; two ----- 1 2.2 (2 rows) SELECT 1 AS one UNION SELECT 1.0::float8; one ----- 1 (1 row) SELECT 1.1 AS two UNION ALL SELECT 2; two ----- 1.1 2 (2 rows) SELECT 1.0::float8 AS two UNION ALL SELECT 1; two ----- 1 1 (2 rows) SELECT 1.1 AS three UNION SELECT 2 UNION SELECT 3; three ------- 1.1 2 3 (3 rows) SELECT 1.1::float8 AS two UNION SELECT 2 UNION SELECT 2.0::float8 ORDER BY 1; two ----- 1.1 2 (2 rows) SELECT 1.1 AS three UNION SELECT 2 UNION ALL SELECT 2; three ------- 1.1 2 2 (3 rows) SELECT 1.1 AS two UNION (SELECT 2 UNION ALL SELECT 2); two ----- 1.1 2 (2 rows) -- -- Try testing from tables... -- SELECT f1 AS five FROM FLOAT8_TBL UNION SELECT f1 FROM FLOAT8_TBL ORDER BY 1; five ----------------------- -1.2345678901234e+200 -1004.3 -34.84 -1.2345678901234e-200 0 (5 rows) SELECT f1 AS ten FROM FLOAT8_TBL UNION ALL SELECT f1 FROM FLOAT8_TBL; ten ----------------------- 0 -34.84 -1004.3 -1.2345678901234e+200 -1.2345678901234e-200 0 -34.84 -1004.3 -1.2345678901234e+200 -1.2345678901234e-200 (10 rows) SELECT f1 AS nine FROM FLOAT8_TBL UNION SELECT f1 FROM INT4_TBL ORDER BY 1; nine ----------------------- -1.2345678901234e+200 -2147483647 -123456 -1004.3 -34.84 -1.2345678901234e-200 0 123456 2147483647 (9 rows) SELECT f1 AS ten FROM FLOAT8_TBL UNION ALL SELECT f1 FROM INT4_TBL; ten ----------------------- 0 -34.84 -1004.3 -1.2345678901234e+200 -1.2345678901234e-200 0 123456 -123456 2147483647 -2147483647 (10 rows) SELECT f1 AS five FROM FLOAT8_TBL WHERE f1 BETWEEN -1e6 AND 1e6 UNION SELECT f1 FROM INT4_TBL WHERE f1 BETWEEN 0 AND 1000000; five ----------------------- -1004.3 -34.84 -1.2345678901234e-200 0 123456 (5 rows) SELECT CAST(f1 AS char(4)) AS three FROM VARCHAR_TBL UNION SELECT f1 FROM CHAR_TBL ORDER BY 1; three ------- a ab abcd (3 rows) SELECT f1 AS three FROM VARCHAR_TBL UNION SELECT CAST(f1 AS varchar) FROM CHAR_TBL ORDER BY 1; three ------- a ab abcd (3 rows) SELECT f1 AS eight FROM VARCHAR_TBL UNION ALL SELECT f1 FROM CHAR_TBL; eight ------- a ab abcd abcd a ab abcd abcd (8 rows) SELECT f1 AS five FROM TEXT_TBL UNION SELECT f1 FROM VARCHAR_TBL UNION SELECT TRIM(TRAILING FROM f1) FROM CHAR_TBL ORDER BY 1; five ------------------- a ab abcd doh! hi de ho neighbor (5 rows) -- -- INTERSECT and EXCEPT -- SELECT q2 FROM int8_tbl INTERSECT SELECT q1 FROM int8_tbl; q2 ------------------ 4567890123456789 123 (2 rows) SELECT q2 FROM int8_tbl INTERSECT ALL SELECT q1 FROM int8_tbl; q2 ------------------ 4567890123456789 4567890123456789 123 (3 rows) SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1; q2 ------------------- -4567890123456789 456 (2 rows) SELECT q2 FROM int8_tbl EXCEPT ALL SELECT q1 FROM int8_tbl ORDER BY 1; q2 ------------------- -4567890123456789 456 (2 rows) SELECT q2 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q1 FROM int8_tbl ORDER BY 1; q2 ------------------- -4567890123456789 456 4567890123456789 (3 rows) SELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl; q1 ---- (0 rows) SELECT q1 FROM int8_tbl EXCEPT ALL SELECT q2 FROM int8_tbl; q1 ------------------ 4567890123456789 123 (2 rows) SELECT q1 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q2 FROM int8_tbl; q1 ------------------ 4567890123456789 4567890123456789 123 (3 rows) -- -- Mixed types -- SELECT f1 FROM float8_tbl INTERSECT SELECT f1 FROM int4_tbl; f1 ---- 0 (1 row) SELECT f1 FROM float8_tbl EXCEPT SELECT f1 FROM int4_tbl ORDER BY 1; f1 ----------------------- -1.2345678901234e+200 -1004.3 -34.84 -1.2345678901234e-200 (4 rows) -- -- Operator precedence and (((((extra))))) parentheses -- SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl; q1 ------------------- 4567890123456789 123 456 4567890123456789 123 4567890123456789 -4567890123456789 (7 rows) SELECT q1 FROM int8_tbl INTERSECT (((SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl))); q1 ------------------ 4567890123456789 123 (2 rows) (((SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl))) UNION ALL SELECT q2 FROM int8_tbl; q1 ------------------- 4567890123456789 123 456 4567890123456789 123 4567890123456789 -4567890123456789 (7 rows) SELECT q1 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1; q1 ------------------- -4567890123456789 456 (2 rows) SELECT q1 FROM int8_tbl UNION ALL (((SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1))); q1 ------------------- 123 123 4567890123456789 4567890123456789 4567890123456789 -4567890123456789 456 (7 rows) (((SELECT q1 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl))) EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1; q1 ------------------- -4567890123456789 456 (2 rows) -- -- Subqueries with ORDER BY & LIMIT clauses -- -- In this syntax, ORDER BY/LIMIT apply to the result of the EXCEPT SELECT q1,q2 FROM int8_tbl EXCEPT SELECT q2,q1 FROM int8_tbl ORDER BY q2,q1; q1 | q2 ------------------+------------------- 4567890123456789 | -4567890123456789 123 | 456 (2 rows) -- This should fail, because q2 isn't a name of an EXCEPT output column SELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1; ERROR: column "q2" does not exist LINE 1: ... int8_tbl EXCEPT SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1... ^ HINT: There is a column named "q2" in table "*SELECT* 2", but it cannot be referenced from this part of the query. -- But this should work: SELECT q1 FROM int8_tbl EXCEPT (((SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1))); q1 ------------------ 4567890123456789 123 (2 rows) -- -- New syntaxes (7.1) permit new tests -- (((((select * from int8_tbl))))); q1 | q2 ------------------+------------------- 123 | 456 123 | 4567890123456789 4567890123456789 | 123 4567890123456789 | 4567890123456789 4567890123456789 | -4567890123456789 (5 rows) -- -- Check handling of a case with unknown constants. We don't guarantee -- an undecorated constant will work in all cases, but historically this -- usage has worked, so test we don't break it. -- SELECT a.f1 FROM (SELECT 'test' AS f1 FROM varchar_tbl) a UNION SELECT b.f1 FROM (SELECT f1 FROM varchar_tbl) b ORDER BY 1; f1 ------ a ab abcd test (4 rows) -- This should fail, but it should produce an error cursor SELECT '3.4'::numeric UNION SELECT 'foo'; ERROR: invalid input syntax for type numeric: "foo" LINE 1: SELECT '3.4'::numeric UNION SELECT 'foo'; ^ -- -- Test that expression-index constraints can be pushed down through -- UNION or UNION ALL -- CREATE TEMP TABLE t1 (a text, b text); CREATE INDEX t1_ab_idx on t1 ((a || b)); CREATE TEMP TABLE t2 (ab text primary key); INSERT INTO t1 VALUES ('a', 'b'), ('x', 'y'); INSERT INTO t2 VALUES ('ab'), ('xy'); set enable_seqscan = off; set enable_indexscan = on; set enable_bitmapscan = off; explain (costs off) SELECT * FROM (SELECT a || b AS ab FROM t1 UNION ALL SELECT * FROM t2) t WHERE ab = 'ab'; QUERY PLAN --------------------------------------------- Append -> Index Scan using t1_ab_idx on t1 Index Cond: ((a || b) = 'ab'::text) -> Index Only Scan using t2_pkey on t2 Index Cond: (ab = 'ab'::text) (5 rows) explain (costs off) SELECT * FROM (SELECT a || b AS ab FROM t1 UNION SELECT * FROM t2) t WHERE ab = 'ab'; QUERY PLAN --------------------------------------------------- HashAggregate -> Append -> Index Scan using t1_ab_idx on t1 Index Cond: ((a || b) = 'ab'::text) -> Index Only Scan using t2_pkey on t2 Index Cond: (ab = 'ab'::text) (6 rows) reset enable_seqscan; reset enable_indexscan; reset enable_bitmapscan; -- Test constraint exclusion of UNION ALL subqueries explain (costs off) SELECT * FROM (SELECT 1 AS t, * FROM tenk1 a UNION ALL SELECT 2 AS t, * FROM tenk1 b) c WHERE t = 2; QUERY PLAN --------------------------- Append -> Seq Scan on tenk1 b (2 rows) -- Test that we push quals into UNION sub-selects only when it's safe explain (costs off) SELECT * FROM (SELECT 1 AS t, 2 AS x UNION SELECT 2 AS t, 4 AS x) ss WHERE x < 4; QUERY PLAN -------------------------------------------- Unique -> Sort Sort Key: (1), (2) -> Append -> Result -> Result One-Time Filter: false (7 rows) SELECT * FROM (SELECT 1 AS t, 2 AS x UNION SELECT 2 AS t, 4 AS x) ss WHERE x < 4; t | x ---+--- 1 | 2 (1 row) explain (costs off) SELECT * FROM (SELECT 1 AS t, generate_series(1,10) AS x UNION SELECT 2 AS t, 4 AS x) ss WHERE x < 4 ORDER BY x; QUERY PLAN -------------------------------- Sort Sort Key: ss.x -> Subquery Scan on ss Filter: (ss.x < 4) -> HashAggregate -> Append -> Result -> Result (8 rows) SELECT * FROM (SELECT 1 AS t, generate_series(1,10) AS x UNION SELECT 2 AS t, 4 AS x) ss WHERE x < 4 ORDER BY x; t | x ---+--- 1 | 1 1 | 2 1 | 3 (3 rows) explain (costs off) SELECT * FROM (SELECT 1 AS t, (random()*3)::int AS x UNION SELECT 2 AS t, 4 AS x) ss WHERE x > 3; QUERY PLAN ---------------------------------------------------------------------------- Subquery Scan on ss Filter: (ss.x > 3) -> Unique -> Sort Sort Key: (1), (((random() * 3::double precision))::integer) -> Append -> Result -> Result (8 rows) SELECT * FROM (SELECT 1 AS t, (random()*3)::int AS x UNION SELECT 2 AS t, 4 AS x) ss WHERE x > 3; t | x ---+--- 2 | 4 (1 row)