sed global substitution for ' character

Hi all,

I have a text file containing sql commands. I want to use sed to replace the " character with the ' character. But when i run the command below it just replaces it with a space? Do i have the escape the ' character if i want to use it?

cat sql.txt

update customer set custid = 'test" where number = 50041;
update customer set custid = 'test2" where number = 50042;
update customer set custid = 'test3" where number = 10393;

$ cat sql.txt | sed 's/"/'/g

update customer set custid = 'test where number = 50041;
update customer set custid = 'test2 where number = 50042;
update customer set custid = 'test3 where number = 10393;

Try this:

sed "s/\"/'/" sql.txt > newfile.txt

Regards