subselect.sql

关系型数据库 Postgresql 6.5.2

--
-- Subselects
--

SELECT 1 AS one WHERE 1 IN (SELECT 1);

SELECT 1 AS zero WHERE 1 NOT IN (SELECT 1);

SELECT 1 AS zero WHERE 1 IN (SELECT 2);

-- Set up some simple test tables

CREATE TABLE SUBSELECT_TBL (
  f1 integer,
  f2 integer,
  f3 float
);

INSERT INTO SUBSELECT_TBL VALUES (1, 2, 3);
INSERT INTO SUBSELECT_TBL VALUES (2, 3, 4);
INSERT INTO SUBSELECT_TBL VALUES (3, 4, 5);
INSERT INTO SUBSELECT_TBL VALUES (1, 1, 1);
INSERT INTO SUBSELECT_TBL VALUES (2, 2, 2);
INSERT INTO SUBSELECT_TBL VALUES (3, 3, 3);
INSERT INTO SUBSELECT_TBL VALUES (6, 7, 8);
INSERT INTO SUBSELECT_TBL VALUES (8, 9, NULL);

SELECT '' AS eight, * FROM SUBSELECT_TBL;

-- Uncorrelated subselects

SELECT '' AS two, f1 AS "Constant Select" FROM SUBSELECT_TBL
  WHERE f1 IN (SELECT 1);

SELECT '' AS six, f1 AS "Uncorrelated Field" FROM SUBSELECT_TBL
  WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL);

SELECT '' AS six, f1 AS "Uncorrelated Field" FROM SUBSELECT_TBL
  WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL WHERE
    f2 IN (SELECT f1 FROM SUBSELECT_TBL));

-- Correlated subselects

SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
  FROM SUBSELECT_TBL
  WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL WHERE f2 = f1);

SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
  FROM SUBSELECT_TBL
  WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL WHERE CAST(f2 AS float) = f3);

SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
  FROM SUBSELECT_TBL
  WHERE f1 IN (SELECT f2 FROM SUBSELECT_TBL WHERE f2 = CAST(f3 AS integer));

SELECT '' AS five, f1 AS "Correlated Field"
  FROM SUBSELECT_TBL
  WHERE (f1, f2) IN (SELECT f2, CAST(f3 AS int4) FROM SUBSELECT_TBL WHERE f3 IS NOT NULL);

SELECT '' AS three, f1 AS "Correlated Field"
  FROM SUBSELECT_TBL
  WHERE (f1, f2) NOT IN (SELECT f2, CAST(f3 AS int4) FROM SUBSELECT_TBL WHERE f3 IS NOT NULL);

--
-- Use some existing tables in the regression test
--

SELECT '' AS eight, ss.f1 AS "Correlated Field", ss.f3 AS "Second Field"
  FROM SUBSELECT_TBL ss
  WHERE f1 NOT IN (SELECT f1 FROM INT4_TBL WHERE f1 != ss.f1);