Use like with PDO on JSON-String - php

Question

Actualy I know how to use LIKE statement with PDO
Now I have a DB-Table called e.g. foobar
foobar contains a JSON-String like:
{"firstname":"foo","email":"aaa#aaa.aa","lastname":"bar"}
Now before I call my INSERT on the table I want to check if the Email is already in use.
$pdo->query("SELECT * FROM myTable WHERE foobar LIKE ?", array('%' . $email . '%'));
as you can see, I pass the email into the pdo query.
Notice ->query is my custom function that handles some stuff. In this case its not important to know what happens.
The problem I have is:
If the entry like above exists then its not possible anymore to add an email thats like:
aa#aaa.aa
^^....only two A's
So I thought I can simply change
array('%' . $email . '%')
to
array('%"' . $email . '"%')
but this doesnt work. Is there a way I can check the whole string part ?
{"firstname":"foo","email":"aaa#aaa.aa","lastname":"bar"}

Answer 1

If you can't break the JSON fields into their own columns, then I would suggest a JSON column type. It's native to MySQL, super fast for JSON of this size, and no more difficult to use than something like jq on the command line.
If that's not an option, I would use a REGEXP:
mysql> select * from foobar;
+-----------------------------------------------------------+
| json |
+-----------------------------------------------------------+
| {"firstname":"foo","email":"aaa#aaa.aa","lastname":"bar"} |
| {"firstname":"FOO","email":"aa#aaa.aa","lastname":"BAR"} |
+-----------------------------------------------------------+
mysql> select * from foobar where json regexp '"email":"aa#aaa.aa"';
+----------------------------------------------------------+
| json |
+----------------------------------------------------------+
| {"firstname":"FOO","email":"aa#aaa.aa","lastname":"BAR"} |
+----------------------------------------------------------+
1 row in set (0.00 sec)
This is serviceable, but hardly bullet-proof and, to borrow an excellent turn of phrase, will murder performance on anything but trivial row sets.