oracle中动态sql中的链接语句

Question

我遇到了以下用于在 oracle 中创建过程的语法。我想知道语法中使用的 a' 、 q'a 、 q'z 和 z' 是什么。

谁能解释一下这些构造的用法。

**

EXECUTE IMMEDIATE 'CREATE OR REPLACE PROCEDURE "demoproc" '|| '( FIXCARD in number DEFAULT 0, INC in number DEFAULT 0 ) '|| 'AUTHID DEFINER IS '|| 'CARD NUMBER; '|| 'FOWNER VARCHAR2(128) := '|| ' SYS_CONTEXT(''USERENV'',''CURRENT_SCHEMA''); '|| 'BEGIN  '|| 'EXECUTE IMMEDIATE '|| ''' EXPLAIN PLAN FOR '' || '|| q'z q'a SELECT a' || q'a z' || q'z "demotab"."a" AS "F_NO", 
:B7 a' || q'a z' || q'z AS "P_NO" 
FROM "demotab" "demotab" 
WHERE ( 
  a' || q'a z' || q'z "demotab"."b" = :B17 AND 
  a' || q'a z' || q'z "demotab"."c" = :B2 AND 
  a' || q'a z' || q'z "demotab"."d" = :B16 
) a' ;

**

注意：语法可能不完整。

Answer 1

此语法用于准确处理引号之间的字符串；您决定用作分隔符的字符，然后在字符串的开头和结尾使用它；一些例子：

select 'quote here: ''' , 'double quote'from dual union all
select q'@quote here: ''@', 'q syntax, double quote means two quotes' from dual union all
select q'@quote here: '@', 'q syntax, no need fou double quotes' from dual union all
select 'two quotes here: ''''', 'same thing to have two quotes' from dual union all
select q'@two quotes here: ''@', 'and two quotes with q syntax ' from dual union all
select q'@this is the delimiter char: @.@', 'the delimiter character can be used wherever in the string' from dual union all
select q'@@delimiter is in the beginning and in the end@@', 'you have to double the delimiter if you want it in the end or beginning' from dual

您可以查看文档 here

Answer 2

q' ' 是一种用嵌入的引号引用字符串文字的方法
例如

select q'x It's a string x' From dual;

It's a string
语法为 q'[...]'，其中“[”和“]”是示例中的字符 a' 和 z'。因此 select q'z execute immediate q'a SELECT count(1) from dual a'z' from dual 变成 execute immediate q'a SELECT count(1) from dual a'

示例查询下方

-- quoting string literals (new from 10G)

select q'aIt's string with embedded quotesa' from dual -- string terminated by chacter "a"
union all
select 'It''s string with embedded quotes' from dual--quotes using a 2 quotes
union all
select q'z execute immediate q'a SELECT count(1) from dual a'z' from dual ; -- your example

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