Update table

Recommended - do this in a transaction.

Here we change the type of a column such as VARCHAR(8) to VARCHAR(1024). We have to create an new column, copy the data to it and then get rid of the old column and rename the new one.

• query.sql

    LOCK table_name;
    ALTER TABLE table_name ADD COLUMN column_new column_type;
    UPDATE table_name SET column_new = column_name;
    ALTER TABLE table_name DROP column_name;
    ALTER TABLE table_name RENAME column_new TO column_name;