Php Sql 使 select 语句不区分大小写

Question

So i basically trying to check if username exists or not but problem is people impersonating others by changing capitalazation I need prevent that i read some answers but they for "LIKE" operator in sql not the

SELECT * FROM users WHERE nick=? LIMIT 1

Ho i can make this return true on different capitilization too Example: test exist on database but if users try to register teST it should return it exists or tEsT

[Database]

I tried doing this:

$user_check_query = "SELECT * FROM users WHERE nick COLLATE utf8_bin = ? LIMIT 1";
$dts = $db->prepare($user_check_query);
$dts->bind_param('s', $nick);
$dts->execute();

It still does not help.

Answer 1

Try with a binary collation:

SELECT * 
  FROM users 
  WHERE username COLLATE utf8_bin = 'NicK'

Answer 2

if your column is already has collation that is not case sensitive, then the query should be ok, if it is case sensitive you can change your query

SELECT * FROM users WHERE lower(username) =lower('nick') LIMIT 1

but to stop that you need to make a unique constraint on that column:

alter table users 
add constraint unique_usernames UNIQUE (username) 

considering collation is not case sensitive.