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oracle集合union、union all、intersect、minus

来源:中国IT实验室 作者:佚名 发表于:2012-08-31 09:41  点击:
oracle集合union、union all、intersect、minus oracle中集合的效率比普通的比较要高 测试案例 --测试表数据 www.2cto.com SQL select stuid from zr_stu; STUID ----------- 1 2 3 4 5 6 7 7 rows selected Executed in 0.14 seconds --表数据 SQL select st
oracle集合union、union all、intersect、minus    oracle中集合的效率比普通的比较要高
    测试案例
    --测试表数据
    www.2cto.com
    SQL> select stuid from zr_stu;
    STUID
    -----------
    1
    2
    3
    4
    5
    6
    7
    7 rows selected
    Executed in 0.14 seconds
    --表数据
    SQL> select stuid from zr_stu where stuid > 3;
    STUID
    -----------
    4
    5
    6
    7
    www.2cto.com
    Executed in 0.047 seconds
    SQL> select stuid from zr_stu where stuid < 6;
    STUID
    -----------
    1
    2
    3
    4
    5
    Executed in 0.109 seconds
    --union
    www.2cto.com
    SQL> select stuid from zr_stu where stuid > 4 union select stuid from zr_stu where stuid < 6;
    STUID
    ----------
    1
    2
    3
    4
    5
    6
    7
    7 rows selected
    Executed in 0.031 seconds
    --union all
    SQL> select stuid from zr_stu where stuid > 4
    2  union all
    3  select stuid from zr_stu where stuid < 6;
    STUID
    ----------
    5
    6
    7
    1
    2
    3
    4
    5
    www.2cto.com
    8 rows selected
    Executed in 0.156 seconds
    --intersect
    SQL> select stuid from zr_stu where stuid > 4
    2  intersect
    3  select stuid from zr_stu where stuid < 6;
    STUID
    ----------
    5
    Executed in 0.078 seconds
    www.2cto.com
    --minus
    SQL> select stuid from zr_stu where stuid > 4
    2  minus
    3  select stuid from zr_stu where stuid < 6;
    STUID
    ----------
    6
    7
    Executed in 0.062 seconds

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