Laravel will report an error when using orderBy in eloquent

$datum = Coupon::orderBy("create_at","desc")->get();
SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near "orders by `create_at` desc" at line 1 (SQL: select * from `st_coupon` where `st_coupon`.`delete_at` is null orders by `create_at` desc)

laravel version 5.6 php 7.2

is the reason why the database operation compiles orderBy to orders by,?

Mar.21,2021

I ask two questions:
whether 1.created_at is created_at?
where the 2.sqlwhere statement comes from, and whether the code is not fully pasted

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3ee09-409d6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3ee09-409d6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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