Hosting Operations

Show MySQL Database Sizes

Disk usage is rising and you need to know which MySQL schemas are largest.

Command

mysql -e "select table_schema, round(sum(data_length + index_length)/1024/1024, 1) as mb from information_schema.tables group by table_schema order by mb desc;"

What changed

Nothing changes. MySQL prints schema sizes.

Danger

safe

When to use it

Use when storage alerts fire, backups grow, or migrations unexpectedly increase disk usage.

When not to use it

Do not use schema size alone to identify the exact table or index growth source.

Undo or recovery

No undo needed because this command is read-only.

Expected output

A sorted list of schema names and approximate size in MiB.

demo script

Disposable terminal steps

df -h /var/lib/mysql
mysql -e "select table_schema, round(sum(data_length + index_length)/1024/1024, 1) as mb from information_schema.tables group by table_schema order by mb desc;"
mysql -e "show databases;"

Terminal transcript Demo JSON

simulated output

What it looks like

disposable vessel

::fixture-ready::
$ df -h /var/lib/mysql
Filesystem      Size  Used Avail Use% Mounted on
/dev/vdb1        80G   59G   17G  78% /var/lib/mysql
::exit-code::0
$ mysql -e "select table_schema, round(sum(data_length + index_length)/1024/1024, 1) as mb from information_schema.tables group by table_schema order by mb desc;"
table_schema	mb
shop	512.4
analytics	240.8
mysql	18.2
::exit-code::0
$ mysql -e "show databases;"
Database
analytics
information_schema
mysql
shop
::exit-code::0

YouTube Short

Find the biggest MySQL schema.

When MySQL storage grows, get the schema-level view before drilling into individual tables.

experiments

A/B tests to run

Metric: linkedin_click_through_rate

A: The storage alert needed a database name.

B: Find the largest MySQL schema first.