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  • Oracle-函数Decode进行多值判断

    decode函数比较表达式和搜索字,如果匹配,返回结果;如果不匹配,返回default值;如果未定义default值,则返回空值

    Decode函数的语法结构如下:

    decode (expression, search_1, result_1)
    decode (expression, search_1, result_1, search_2, result_2)
    decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n)
    decode (expression, search_1, result_1, default)
    decode (expression, search_1, result_1, search_2, result_2, default)
    decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n, default)

    decode函数比较表达式和搜索字,如果匹配,返回结果;如果不匹配,返回default值;如果未定义default值,则返回空值。
    以下是一个简单测试,用于说明Decode函数的用法:

    SQL> create table t as select username,default_tablespace,lock_date from dba_users;
    Table created.
    SQL> select * from t;
    USERNAME                       DEFAULT_TABLESPACE             LOCK_DATE
    ------------------------------ ------------------------------ ---------
    SYS                            SYSTEM
    SYSTEM                         SYSTEM
    OUTLN                          SYSTEM
    CSMIG                          SYSTEM
    SCOTT                          SYSTEM
    EYGLE                          USERS
    DBSNMP                         SYSTEM
    WMSYS                          SYSTEM                         20-OCT-04
    8 rows selected.
    
    SQL> select username,decode(lock_date,null,"unlocked","locked") status from t;
    USERNAME                       STATUS
    ------------------------------ --------
    SYS                            unlocked
    SYSTEM                         unlocked
    OUTLN                          unlocked
    CSMIG                          unlocked
    SCOTT                          unlocked
    EYGLE                          unlocked
    DBSNMP                         unlocked
    WMSYS                          locked
    8 rows selected.
    SQL> select username,decode(lock_date,null,"unlocked") status from t;
    USERNAME                       STATUS
    ------------------------------ --------
    SYS                            unlocked
    SYSTEM                         unlocked
    OUTLN                          unlocked
    CSMIG                          unlocked
    SCOTT                          unlocked
    EYGLE                          unlocked
    DBSNMP                         unlocked
    WMSYS
    8 rows selected.

    文章转载http://www.jb51.net/article/36427.htm

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  • 原文地址:https://www.cnblogs.com/hwaggLee/p/5335967.html
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