sql_queries << 'UPDATE shared SET user_from = $1 WHERE user_from = $2;'
sql_queries << 'UPDATE shared SET user_which = $1 WHERE user_which = $2;'
sql_queries << 'UPDATE shared SET user_from = $1 WHERE user_from = $2;'
sql_queries << 'UPDATE shared SET user_which = $1 WHERE user_which = $2;'