How do I pass a variable to a mysql script?

Like this:

set @department := 'Engineering';

Then, reference @department wherever you need to in script.sql:

update employee set salary = salary + 10000 where department = @department;

    #!/bin/bash

    #verify the passed params
    echo 1 cmd arg : $1
    echo 2 cmd arg : $2

    export db=$1
    export tbl=$2

    #set the params ... Note the quotes ( needed for non-numeric values )
    mysql -uroot -pMySecretPaassword \
    -e "set @db='${db}';set @tbl='${tbl}';source run.sql ;" ;

    #usage: bash run.sh my_db my_table
    #
    #eof file: run.sh

    --file:run.sql

    SET @query = CONCAT('Select * FROM ', @db , '.' , @tbl ) ;
    SELECT 'RUNNING THE FOLLOWING query : ' , @query ;
    PREPARE stmt FROM @query;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;

    --eof file: run.sql

you can re-use the whole concept from from the following project