[SOLVED] Query syntax (qoutes)

[hostfreak]

I know to use single quotes around values in a query (unless an integer). I'm not sure why though. I did know, but it became habit so I forgot why it actually should be done. I think it may have something to do with the escape sequences?

[rajivgonsalves]

I do not think its because of the escape sequence maybe because its treated as a string same as php not too sure do will check it up

[hostfreak]

Yeah, after posting this I ruled the escape sequences out. I've checked the mysql manual, but it's like trying to find a needle in a haystack.

 

It probably does have something to do with the way mysql parses the values.

[trq]

Values are generally strings (unless they are ints), string in sql need to be surrounded in quotes, just as they do in php.

[hostfreak]

Another thing that confuses me is that in php you can only parse a variable in double quotes unless you use the concatenation operator. However, if your doing a query (mysql_query) it will parse the variable surrounded by the single quotes.

 

I am assuming it's only within the mysql_query function that php will parse the variable like this? Do to the fact that inside that function, the quotes will be irrelevant (being as they will then be parsed by mysql)?

[obsidian]

Another thing that confuses me is that in php you can only parse a variable in double quotes unless you use the concatenation operator. However, if your doing a query (mysql_query) it will parse the variable surrounded by the single quotes.

 

I am assuming it's only within the mysql_query function that php will parse the variable like this? Do to the fact that inside that function, the quotes will be irrelevant (being as they will then be parsed by mysql)?

 

Keep in mind that the PHP parser is interpreting the entire string before it gets sent to the MySQL query. So, when you have a variable within the single quotes, PHP only knows that it is part of a larger string within the double quotes. If you were to echo the SQL statement out to the screen, you would see what is actually sent to the MySQL parser:

<?php
$name = 'Obsidian';
$sql = "SELECT * FROM users WHERE username = '{$name}'";
echo $sql; // SELECT * FROM users WHERE username = 'Obsidian'
?>

[hostfreak]

Makes perfect sense now. Thanks for the clarification thus far guys.

 

Only one more question and I think I'll be good. As far as the values needing to be surrounded by quotes in mysql as well, how come it will not give off an error if a value isn't surrounded by quotes?

[trq]

It will throw an error if the value is expected to be within quotes.

[hostfreak]

Alright, got it. Once again, thanks.