如何在PHP查询中使用通配符

Question

I have a table filter feature in PHP club membership webpage. I made it so the user can filter the table and choose which members to display in a table. For example, he can choose the country or state where the member is from then hit display. I am using a prepared statement.

The problem is, I need to use wildcards to make the coding easier. How do I use a wildcard in PHP MySQL query? I will use wildcards for example if the user does NOT want specific country but instead he wants to display all members from all countries.

I know not specifying the WHERE country= will automatically select any countries but I already constructed it so each controls like the SELECT control for country already has a value like "CA" or "NY" and "*" if the user leaves that control under "All Countries". This value when submitted is then added to the query like:

$SelectedCountry = $_POST["country"];
sql .= " WHERE country=" . $SelectedCountry;

But the problem is using WHERE country=* doesn't seem to work. No errors, just doesn't work. Is "*" the wildcard in PHP MySQL?

Answer 1

The * is not a wildcard in SQL when comparing with the = operator. You can use the like operator and pass a % to allow for anything.

When doing this the % should be the only thing going to the bind. $Bind_country = "'%'"; is incorrect because the driver is already going to quote the value and escape the quotes. So your query would come out as:

WHERE country ='\'%\''

The = also needs to be a like. So you want

$bind_country = '%'; 

and then the query should be:

$sql = 'select * from table where country like ?';

If this were my application I would build the where part dynamically.