Alter charset and collation in all columns in all tables in MySQL

Solution 1:

First of all, don't just take my word for it! Test my suggestion out with this:

select CONCAT('alter table ',TABLE_SCHEMA,'.',TABLE_NAME,' charset=utf8;') from information_schema.TABLES WHERE TABLE_SCHEMA != 'information_schema' limit 10; select CONCAT('alter table ',TABLE_SCHEMA,'.',TABLE_NAME,' alter column ',COLUMN_NAME,' charset=utf8;') from information_schema.COLUMNS WHERE TABLE_SCHEMA != 'information_schema' limit 10;

If you feel good with the outcome of that, remove the limit clauses and save the output to an SQL script or, get fancy and pipe the output directly to mysql similar to what I demonstrate here. That would look like this:

mysql -B -N --host=prod-db1 --user=admin --password=secret -e "select CONCAT('alter table ',TABLE_SCHEMA,'.',TABLE_NAME,' charset=utf8;') from information_schema.TABLES WHERE TABLE_SCHEMA != 'information_schema'; select CONCAT('alter table ',TABLE_SCHEMA,'.',TABLE_NAME,' alter column ',COLUMN_NAME,' charset=utf8;') from information_schema.COLUMNS WHERE TABLE_SCHEMA != 'information_schema';" | mysql --host=prod-db1 --user=admin --password=secret

When you start thinking about using valid SQL to generate valid SQL, it changes the whole game. You will be amazed by how many uses you find for it.

Solution 2:

Actually, you can use CONVERT TO on a table to have it convert all columns within that table to the charset and collation.

SELECT CONCAT('ALTER TABLE ',TABLE_SCHEMA,'.',TABLE_NAME,' CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;') FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'databasename';

Also, it makes more sense to me to select the actual database you want to do this on. So this:

... WHERE TABLE_SCHEMA = 'databasename';

rather than this:

... WHERE TABLE_SCHEMA != 'information_schema';

But I guess if you really wanted to do it on all tables, you could use the former. Seems a bit heavy handed to me though. :)

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Solution 3:

To change collation on all columns i used

SELECT CONCAT(  'ALTER TABLE ',  `TABLE_NAME` ,  ' CHANGE `',  `COLUMN_NAME` ,  '` `',`COLUMN_NAME` ,  '` ',  `DATA_TYPE` ,  '(',  `CHARACTER_MAXIMUM_LENGTH` ,  ') CHARACTER SET utf8 COLLATE utf8_swedish_ci ;' ) FROM  `COLUMNS` WHERE  `TABLE_SCHEMA` =  <schema> AND  `COLLATION_NAME` !=  'utf8_swedish_ci' ORDER BY  `TABLE_NAME` ,  `ORDINAL_POSITION` ;