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 createdSQL> select * from t;USERNAME DEFAULT_TABLESPACE LOCK_DATE ------------------------------ ------------------------------ -----------SYS SYSTEMSYSTEM SYSTEM DBSNMP SYSTEM SCOTT SYSTEM ------------------------------ ------------------------------ ----------- ------------------------------ -------- SYS unlocked SYSTEM unlocked DBSNMP unlocked
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