How to save MySQL query output to excel or .txt file?

You can write following codes to achieve this task:

SELECT ... FROM ... WHERE ... 
INTO OUTFILE 'textfile.csv'
FIELDS TERMINATED BY '|'

It export the result to CSV and then export it to excel sheet.

From Save MySQL query results into a text or CSV file:

MySQL provides an easy mechanism for writing the results of a select statement into a text file on the server. Using extended options of the INTO OUTFILE nomenclature, it is possible to create a comma separated value (CSV) which can be imported into a spreadsheet application such as OpenOffice or Excel or any other application which accepts data in CSV format.

Given a query such as

SELECT order_id,product_name,qty FROM orders

which returns three columns of data, the results can be placed into the file /tmp/orders.txt using the query:

SELECT order_id,product_name,qty FROM orders
INTO OUTFILE '/tmp/orders.txt'

This will create a tab-separated file, each row on its own line. To alter this behavior, it is possible to add modifiers to the query:

SELECT order_id,product_name,qty FROM orders
INTO OUTFILE '/tmp/orders.csv'
FIELDS TERMINATED BY ','
ENCLOSED BY '"'
LINES TERMINATED BY '\n'

In this example, each field will be enclosed in double quotes, the fields will be separated by commas, and each row will be output on a new line separated by a newline (\n). Sample output of this command would look like:

"1","Tech-Recipes sock puppet","14.95" "2","Tech-Recipes chef's hat","18.95"

Keep in mind that the output file must not already exist and that the user MySQL is running as has write permissions to the directory MySQL is attempting to write the file to.

Syntax

   SELECT Your_Column_Name
    FROM Your_Table_Name
    INTO OUTFILE 'Filename.csv'
    FIELDS TERMINATED BY ','
    ENCLOSED BY '"'
    LINES TERMINATED BY '\n'

Or you could try to grab the output via the client:

You could try executing the query from the your local client and redirect the output to a local file destination:

mysql -user -pass -e "select cols from table where cols not null" > /tmp/output

Hint: If you don't specify an absoulte path but use something like INTO OUTFILE 'output.csv' or INTO OUTFILE './output.csv', it will store the output file to the directory specified by show variables like 'datadir';.