# MySQL

We always recommend to dump and import through the command line, if possible. This documentation will explain how to do this securely.

For most databases (only a couple of gigabytes big), you can dump the database with this command:

mysqldump --single-transaction --triggers --routines --events -y DBNAME > DBNAME.sql

For larger databases (tens of gigabytes or bigger), compress the database to conserve disk space and speed up transfer:

mysqldump --single-transaction --triggers --routines --events -y DBNAME | gzip -3 -v > DBNAME.gz

Use scp to transfer the file:

scp FileName user@HostnameOrIP:Path/To/Folder

Hint: To place the file in the user's home directory, remove everything after the colon.

mysql DBNAME < DBNAME.sql

Or, if compressed:

gunzip -c DBNAME.gz | mysql DBNAME

Hint: Large databases can take time to import, especially on high-load servers.

Use nohup to ensure the dump or import continues if the connection is lost.

Use screen to allow session sharing or recovery:

• Create a session:

  screen -S <session_name>

• Disconnect (keep running):

  Ctrl + A, then D

• Reattach or take over session:

  screen -dr <session_name>

• List sessions:

  screen -ls

Avoid password prompts by setting up SSH key authentication.

Access denied; you need (at least one of) the SUPER privilege(s) for this operation

This is caused by routines, views, or triggers defined with a definer the user cannot access.

Solution: Strip the definer using sed:

mysqldump --routines --single-transaction --triggers --routines --events -y DBNAME | sed -e 's/DEFINER=[^*]*\*/\*/g' > DBNAME.sql

Or with compression:

mysqldump --single-transaction --triggers --routines --events -y DBNAME | sed -e 's/DEFINER=[^*]*\*/\*/g' | gzip -3 -v > DBNAME.gz

If you already have the file:

cat DBNAME.sql | sed -e 's/DEFINER=[^*]*\*/\*/g' | mysql DBNAME

Compressed file:

gunzip -c DBNAME.gz | sed -e 's/DEFINER=[^*]*\*/\*/g' | mysql DBNAME

Row size too large (> 8126). Changing some columns to TEXT or BLOB or using ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED may help.

Caused by limits on row size when using ROW_FORMAT=COMPACT.

Fix during import:

cat DBNAME.sql | sed -e 's/ROW_FORMAT=COMPACT/ROW_FORMAT=DYNAMIC/g' | mysql DBNAME

Compressed file:

gunzip -c DBNAME.gz | sed -e 's/ROW_FORMAT=COMPACT/ROW_FORMAT=DYNAMIC/g' | mysql DBNAME