20.1, single and double quotes oracle support, but the two are different;
20.2, acting double quotes:
1, keywords, object names, field names with double quotation marks schematic Oracle will be strictly case-sensitive, otherwise Oracl by default capitalized;
2, double quotation marks around keywords:
select "sysdate" from dual; 等同于 select sysdate from dual;
The following are not output time, output will sysdate string.
select 'sysdate' from dual;
3, double quotation marks around field names:
select * from emp where "ENAME" = scott;
Since strict double quotes prompted oracle case-sensitive, the following versa;
select * from emp where "ename" = scott;
20.3, the role of single quotes in Oracle:
1, a reference to a string constant, that is, to define the start and end of a string;
E.g:
select * from table_name where id=1123;
# This represents the query is digital
select * from table_name where id='1123';
# This is the character representing query
2, the escape character, the character appears followed (single quote) escaped
Two single quotes can be used as a single quote escape use, meaning that a real, no special features of single quotes;
E.g:
select substr('I''am a pig',1,4)