Excel and MySQL can read and write delimited text (CSV) files. To load a text file into MySQL, use the LOAD DATA INFILE statement.
To create a text file from MySQL, use the SELECT INTO OUTFILE syntax, or the ability of the client to write or redirect to a file. For example:
$ mysql -e "SELECT * FROM tblname" > outfile.txt
Graphical clients such as MySQL Workbench can also send the results of a query to a file.
Another way to export query results to a file on the client host is to use the mysql_to_text.pl utility, available in the recipes distribution. That program has options that enable you to specify the output format explicitly. To export a query result as an Excel spreadsheet or XML document, use mysql_to_excel.pl and mysql_to_xml.pl utilities.