Update column in HIVE

Question

I have a table in php which is in this format:

CREATE EXTERNAL TABLE IF NOT EXISTS {$tableName} (fileContent VARCHAR(250), description VARCHAR(250), dimension DOUBLE, fileName VARCHAR(250)) ROW FORMAT DELIMITED FIELDS TERMINATED BY ',' LINES TERMINATED BY '\\n' STORED AS TEXTFILE LOCATION '/var/www/ASOIS_Proiect/metadata/'

I want for a situation to update only description field if fileName='a' and 'size'='12' already exist in database.

Any idea please? I tried to update the file create for insert with command LOAD and flag OVERWRITE but it is not working.