what is the difference between ""and ''?

[Deo.Dy]

Hi,guys!
I have some questions when I operating DB! When i write sql-language I always being confused with the difference between "" and ''?
So,please tell me the difference.Thanks!

[shyam]

u mean single(') and double(") quotes ?

single quotes are used for string literals like in the where clause

select ...
where name = 'jack';

double quotes are used to escape object names that might also be keywords in MySQL eg. when u have a table with order as a column name
select ...
where ...
order by "order"

[guelphdad]

double quotes are used to escape object names that might also be keywords in MySQL eg. when u have a table with order as a column name
select ...
where ...
order by "order"

Really the best scenario is to not use reserved words in the first place.

[Deo.Dy]

Thanks ! It is very kind of you!