Check if mysql database exists, perform action based on result

Question

Is it possible from within a bash script to check if a mysql database exists. Depending on the result then perform another action or terminate the script?

Answer 1

Example script (Thanks to Bill Karwin for the --user and --password comment!):

#!/bin/bash
## --user=XXXXXX --password=XXXXXX *may* not be necessary if run as root or you have unsecured DBs but
##   using them makes this script a lot more portable.  Thanks @billkarwin
RESULT=`mysqlshow --user=XXXXXX --password=XXXXXX myDatabase| grep -v Wildcard | grep -o myDatabase`
if [ "$RESULT" == "myDatabase" ]; then
    echo YES
fi

These are what the commands look like when run at a prompt:

[root@host ~]# mysqlshow myDatabase
Wildcard: myDatabase
+------------------+
|    Databases     |
+------------------+
| myDatabase       |
+------------------+

If no DB exists, the output will look like this:

[root@host ~]# mysqlshow myDatabase
Wildcard: myDatabase
+-----------+
| Databases |
+-----------+
+-----------+

Then, parse the output and do what you need to based on if it exists or not!

Answer 2

I give +1 to answer by @chown, but here's another alternative: If the bash script is running locally with the MySQL instance, and you know the path to the datadir, you can test:

if [ -d /var/lib/mysql/databasename ] ; then 
    # Do Stuff ...
fi

This also assumes your shell user running the script has filesystem-level privileges to read the contents of the MySQL datadir. This is often the case, but it is not certain.

Answer 3

I couldn't get the accepted answer work for me (the grep in the quotes didn't work), so here is my version:

RESULT=`mysql -u $USER -p$PASSWORD --skip-column-names -e "SHOW DATABASES LIKE 'myDatabase'"`
if [ "$RESULT" == "myDatabase" ]; then
    echo "Database exist"
else
    echo "Database does not exist"
fi

I used the option --skip-column-names to remove the column names from the result.

Answer 4

YES

for db in $(mysql -u -p -N <<<"show databases like '%something%'")
do
  case $db in 
    "something")
      // do something
    ;;
    "something else")
      // do something else
    ;;
  esac
done

Answer 5

mysql_user=<you_db_username>
mysql_pass=<you_db_passwrod>
target_db=<your_db_name>
if [ "`mysql -u${mysql_user} -p${mysql_pass} -e 'show databases;' | grep ${target_db}`" == "${target_db}" ]; then
  echo "Database exist"
else
  echo "Database does not exist"
fi

This executes a MySQL query to get all DB names, then greps to check that the required database exists.

Answer 6

I also used a slightly different version from chown's.

result=$(mysqlshow --user=root --password=12345 dbname | grep -v Wildcard | grep -ow dbname)

The above executes the given command and assigns the returned value to result. And the w option matches dbname exactly.