[Discuz X2.5] It is a safe to do this query does not allow quotation marks resolution

[Discuz X2.5] It is a safe to do this query does not allow quotation marks
You give discuzX2.5 to do two times development, ask you in the self-made table slimy query or to check a string username, how to deal with???

I am currently using: Db::query (' select * from T_username where f_username= '. $username. ' ");

I found that if there were quotes in SQL, it would go wrong. Ask everyone to query their own table, how to write SQL statements ah.

------Solution--------------------
' "Change it.
------Solution--------------------
Db::query ("select * from T_username where f_username= ' $username '");

