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  • exists 的简单介绍

    准备数据:

     1 CREATE TABLE Books(
     2     BookID number,
     3     BookTitle VARCHAR2(20) NOT NULL,
     4     Copyright varchar2(20)
     5 )
     6 INSERT INTO Books VALUES (12786, 'Java',1934);
     7 INSERT INTO Books VALUES (13331, 'MySQL',1919);
     8  INSERT INTO Books VALUES (14356, 'PHP',1966);
     9  INSERT INTO Books VALUES (15729, 'PERL',1932);
    10  INSERT INTO Books VALUES (16284, 'Oracle',1996);
    11  INSERT INTO Books VALUES (17695, 'Pl/SQL',1980);
    12  INSERT INTO Books VALUES (19264, 'JavaScript',1992);
    13  INSERT INTO Books VALUES (19354, 'www.manongjc.com',1993);
    14 
    15 CREATE TABLE AuthorBook(
    16     AuthID NUMBER,
    17     BookID NUMBER
    18     )
    19 
    20 INSERT INTO AuthorBook VALUES (1006, 14356);
    21 INSERT INTO AuthorBook VALUES (1008, 15729);
    22 INSERT INTO AuthorBook VALUES (1009, 12786);
    23 INSERT INTO AuthorBook VALUES (1010, 17695);
    24 INSERT INTO AuthorBook VALUES (1011, 15729);
    25 INSERT INTO AuthorBook VALUES (1012, 19264);
    26 INSERT INTO AuthorBook VALUES (1012, 19354);
    27 INSERT INTO AuthorBook VALUES (1014, 16284); 

    BOOKS表:

    AUTHORBOOK表:

    查询B表ID在A表中的数据

     1 select * from BOOKS B 2 WHERE EXISTS (SELECT * FROM AUTHORBOOK A WHERE A.BOOKID=B.BOOKID) 

    EXISTS后面表示的只有两个值。就是“真”或者“假”。 NOT EXISTS 与EXISTS相反。

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  • 原文地址:https://www.cnblogs.com/bulrush/p/7560141.html
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