Using REPLACE INTO Instead of INSERT INTO in mysqldump

The mysqldump command is a powerful utility in MySQL used for exporting database contents to a file. When dealing with data backups or migrations, it’s crucial to understand various options such as --replace. This option alters the typical behavior of INSERT INTO statements by using REPLACE INTO instead, which allows updating existing rows based on primary key conflicts rather than throwing errors.

Let’s delve into some examples to illustrate the usage of --replace in mysqldump:

Example 1: Exporting a single table with replace:
mysqldump --replace mydatabase mytable > mytable_backup.sql

This command exports the table mytable from the database mydatabase into mytable_backup.sql. If any rows in mytable conflict with existing rows in the destination database during import, they will be replaced.

Example 2: Exporting all databases with replace:
mysqldump --all-databases --replace > alldatabases_backup.sql

This command exports all databases and their tables into alldatabases_backup.sql. The --replace option ensures that any conflicting rows across all databases are replaced during import.

Example 3: Exporting with replace and compression:
mysqldump --replace --all-databases | gzip > alldatabases_backup.sql.gz

Here, the output of mysqldump is piped to gzip for compression into alldatabases_backup.sql.gz. The --replace option remains effective, ensuring integrity during import even after compression.

Example 4: Exporting with replace and specifying host:
mysqldump --replace --host=myhost --user=myuser --password=mypassword mydatabase > mydatabase_backup.sql

This command exports the mydatabase from myhost using specified credentials, ensuring any conflicts in data are resolved using REPLACE INTO.

Verification: To verify if the command executed successfully, you can check the size of the output file created (e.g., mytable_backup.sql or alldatabases_backup.sql.gz). Additionally, you can import the exported SQL file into another MySQL database to ensure that the data integrity is maintained, especially in cases where --replace was utilized.

Also check similar articles.

Quoting Table and Column Names in mysqldump Output
Dumping Quickly without Buffering in mysqldump
Setting Connection Protocol in mysqldump
Connecting to MySQL Port in mysqldump
Providing Password for mysqldump Connection