Drop multiple databases with names matching a pattern

Question

I want to drop all the databases starting with a word.

abc
xyz
cms_db1
cms_db2
cms_xyz
pqr

In the example given above, I will like to drop all

Answer 1

Improved @neurino solution to avoid storing of MySQL credentials in the script and passing them through a command line (it might be visible in the list of processes then)

#!/bin/bash

DB_STARTS_WITH="cms"
MYSQL="mysql"

read -p "Enter MySQL user name: " MYSQL_USER
read -s -p "Enter password: " MYSQL_PASSWORD

CREDENTIALS_FILE="$(mktemp)"
chmod 600 $CREDENTIALS_FILE
cat > $CREDENTIALS_FILE <<- EOM
[client]
user=$MYSQL_USER
password=$MYSQL_PASSWORD
EOM

trap "{ rm -f $CREDENTIALS_FILE; }" EXIT

DATABASES="$(echo "show databases;" | $MYSQL --defaults-file=$CREDENTIALS_FILE)"

for DATABASE in $DATABASES; do
    if [[ $DATABASE =~ ^${DB_STARTS_WITH} ]]; then
        echo Removing $DATABASE...
        echo "drop database $DATABASE" | $MYSQL --defaults-file=$CREDENTIALS_FILE
    fi
done

Answer 2

Linux way:

#!/bin/bash

DB_STARTS_WITH="cms"
MUSER="root"
MPWD="yourpass"
MYSQL="mysql"

DBS="$($MYSQL -u$MUSER -p$MPWD -Bse 'show databases')"
for db in $DBS; do

if [[ "$db" =~ "^${DB_STARTS_WITH}" ]]; then
    echo "Deleting $db"
    $MYSQL -u$MUSER -p$MPWD -Bse "drop database $db"
fi

done

Of course use the drop part at your own risk ;)

Answer 3

Improvising on the excellent answer by @cloakedninjas, for easier retrieval of all the queries to execute in a single string.

Firstly, you can set the maximum value for group_concat_max_len to the maximum possible value, for this particular session:

SET SESSION group_concat_max_len = @@max_allowed_packet;

Now, you can prepare a query string (to execute later) using SQL. Using information_schema, we can get name of all the databases matching the pattern. Now, use Concat() to prepare a single DROP DATABASE .. query, and then utilize Group_Concat() to merge them all into a single string, for easier retrieval.

SELECT GROUP_CONCAT(CONCAT('DROP DATABASE `', SCHEMA_NAME, '`;') 
                    SEPARATOR ' ') AS query_to_execute
FROM information_schema.SCHEMATA
WHERE SCHEMA_NAME LIKE 'cms_%'

Now copy the string in query_to_execute and run it separately.

Answer 4

I would use something like:

echo "SHOW DATABASES LIKE 'cms_%'" \
  | mysql \
  | tail -n +2 \
  | xargs -n1 mysqladmin -f drop

If you don't have your default username and password configured inside ~/my.cnf, you may need to supply the username and password via the -u and -p switches to the mysql/mysqladmin commands above.

(Edit - added -n arg to tail.)