Mysql multi-field query the same text

has field A B C
field content: text plus number
how to query and filter the results with the same text in An and B fields
query the results with the same text in A B C field

May.06,2021

select A,B,C where A=B;
select A,B,C where A=B and A=C;
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-64f5-1b2c56f-2bb12.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b2c56f-2bb12.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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