Replace space with underscore in table

Question

How can I write a SQL query to replace all occurrences of space in a table with underscore and set all characters to lowercase?

Solution

To update a single column in a single table, you can use a combination of LOWER() and REPLACE():

UPDATE table_name SET column_name=LOWER(REPLACE(column_name, ' ', '_'))

To "duplicate" the existing column, and perform the updates on the duplicate (per your question in a comment), you can use MySQL's ALTER command before the UPDATE query:

ALTER TABLE table_name ADD duplicate_column_name VARCHAR(255) AFTER column_name;
UPDATE table_name SET duplicate_column_name = LOWER(REPLACE(column_name, ' ', '_'));

Just be sure to update the data-type in the ALTER command to reflect your actual data-type.

Comments

[mlishn]

would this work for the entire table in one query? Wouldn't be need to iterate through each row to get this working?

[Mark Henry]

first I need to duplicate the column. How do I do that?

[newfurniturey]

@mlishn This will work for an entire column in the given table; If he needs multiple columns in the same table he could append them to the update clause. If he needs multiple tables, he could use either multiple UPDATE clauses - or write a stored procedure that iterates through information_schema.

[mlishn]

@newfurniturey great answer then :)

[newfurniturey]

@mark I've updated my answer to show how to duplicate the column first.