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Q’ 的使用

2018年04月17日 ⁄ 綜合 ⁄ 共 2318字 ⁄ 字型大小 評論關閉

最近在項目經常看見使用q', 於是決定研究一下。 q'是oracle10g才有的新特性。 主要用於把字元串包含起來進行賦值。 特別在dynamic sql中,如果被包含的sql很複雜, 而且有單引號的情況下, 可以簡單的表達,不用去拆分sql,和判斷單雙引號, 給程序的編寫和閱讀帶來很大方便。q'可以支持多種配對分隔符。如#,{},[],/等等。

 

note that: 不管是q',還是原先得single quote, 都支持換行書寫同一個字元串。

 字元串不支持雙引號引用字元串, 而且在字元串中,用雙引號代替單引號的方法好像也不好用。

 

SQL> select 'i am your boyfriend' MESSAGE from dual;

MESSAGE                                                                        
--------------------------------------                                         
i am your boyfriend                                                            

SQL>
SQL> select 'i am "your" boyfriend' MESSAGE from dual;

MESSAGE                                                                        
------------------------------------------                                     
i am "your" boyfriend                                                          

SQL>
SQL>
SQL> select "i am 'your' boyfriend" MESSAGE from dual;
select "i am 'your' boyfriend" MESSAGE from dual
       *
第 1 行出現錯誤:
ORA-00904: "i am 'your' boyfriend": invalid identifier

SQL>
SQL> select 'i am your
  2   boyfriend' MESSAGE from dual;

MESSAGE                                                                        
----------------------------------------                                       
i am your                                                                      
 boyfriend                                                                     
                                                                               

SQL>
SQL> select q'{what the fuck ' are you doing?}' MESSAGE from dual;

MESSAGE                                                                        
------------------------------------------------------------                   
what the fuck ' are you doing?                                                 

SQL>
SQL>
SQL> select q'/what the fuck ' are you doing?/' MESSAGE from dual;

MESSAGE                                                                        
------------------------------------------------------------                   
what the fuck ' are you doing?                                                 

SQL>
SQL> select q'{what the fuck
  2   ' are you doing?}' MESSAGE from dual;

MESSAGE                                                                        
--------------------------------------------------------------                 
what the fuck                                                                  
 ' are you doing?

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