導讀:1

Decode函數的語法結構如下:

復制代碼 代碼如下:

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企業網站建設, default)decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n, default)

decode函數比較表達式和搜索字，如果匹配，返回結果；如果不匹配，返回default值；如果未定義default值，則返回空值。以下是一個簡單測試，用于說明Decode函數的用法:

復制代碼 代碼如下:

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 SYSTEMSYSTEM SYSTEMOUTLN SYSTEMCSMIG SYSTEMSCOTT SYSTEMEYGLE USERSDBSNMP SYSTEMWMSYS SYSTEM 20-OCT-04

8 rows selected.

SQL> select username,decode(lock_date,null,"unlocked","locked") status from t;

USERNAME STATUS------------------------------ --------SYS unl網站建設教程ockedSYSTEM unlockedOUTLN unlockedCSMIG unlockedSCOTT unlockedEYGLE unlockedDBSNMP unlockedWMSYS locked

8 rows selected.

SQL> select username,decode(lock_date,null,"unlocked") status from t;

USERNAME STATUS------------------------------ --------SYS unlockedSYSTEM unlockedOUTLN unlockedCSMIG unlockedSCOTT unlockedEYGLE unlockedDBSNMP unlockedWMSYS

8 rows selected.

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關鍵詞標簽: 標簽 函數