For single table you can do something like this: ALTER TABLE tab CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci; For the whole database I don’t know other method than similar to this: http://www.commandlinefu.com/commands/view/1575/convert-all-mysql-tables-and-fields-to-utf8
I faced a very similar situation in the past and i improve the performance of the operation in this way : Create a new table (using the structure of the current table) with the new column(s) included. execute a INSERT INTO new_table (column1,..columnN) SELECT (column1,..columnN) FROM current_table; rename the current table rename the new table … Read more
I don’t believe you can do it like that but you should be able to use the setval function direction which is what the alter does. select setval(‘sequenceX’, (select max(table_id)+1 from table), false) The false will make it return the next sequence number as exactly what is given.
Pete was almost correct but used the wrong syntax for ‘change’: ALTER TABLE mytable CHANGE `time` `time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP Notice that you must repeat the column name. Also, make sure you are using backticks instead of single quotes to escape the column name time, which prevents it from being interpreted as the … Read more
You cannot alter an index – all you can do is drop the old index (DROP INDEX (indexname) ON (tablename)) re-create the new index with the additional column in it: CREATE UNIQUE NONCLUSTERED INDEX (indexname) ON dbo.YourTableName(columns to include) The ALTER INDEX statement in SQL Server (see docs) is available to alter certain properties (storage … Read more
Something like this: ALTER TABLE dbo.MyTable DROP COLUMN OldComputedColumn ALTER TABLE dbo.MyTable ADD OldComputedColumn AS OtherColumn + 10 Source
Your ALTER TABLE statement implies mysql will have to re-write every single row of the table including the new column. Since you have more than 2 million rows, I would definitely expect it takes a significant amount of time, during which your server will likely be mostly IO-bound. You’d usually find it’s more performant to … Read more
There is no ALTER command for constraints in Postgres. The easiest way to accomplish this is to drop the constraint and re-add it with the desired parameters. Of course any change of the constraint will be run against the current table data. BEGIN; ALTER TABLE t1 DROP CONSTRAINT … ALTER TABLE t1 ADD CONSTRAINT … … Read more
your table: q1 | q2 | q3 | q4 | q5 you can also do ALTER TABLE yourtable ADD q6 VARCHAR( 255 ) after q5
You can easily do this using the following command. Any value of 0 will be turned into a 0 (BIT = false), anything else will be turned into 1 (BIT = true). ALTER TABLE dbo.YourTable ALTER COLUMN YourColumnName BIT The other option would be to create a new column of type BIT, fill it from … Read more