As your data changes over time, SQL provides a way for you to update your corresponding tables and
database schemas by using the
ALTER TABLE statement to add, remove, or modify columns and table
The syntax for adding a new column is similar to the syntax when creating new rows in the
statement. You need to specify the data type of the column along with any potential table constraints
and default values to be applied to both existing and new rows. In some databases like MySQL,
you can even specify where to insert the new column using the
AFTER clauses, though this
is not a standard feature.
ALTER TABLE mytable ADD column DataType OptionalTableConstraint DEFAULT default_value;
Dropping columns is as easy as specifying the column to drop, however, many databases (including Postgres, and SQLite) don't support this feature. Instead you may have to create a new table and migrate the data over.
ALTER TABLE mytable DROP column_to_be_deleted;
If you need to rename the table itself, you can also do that using the
RENAME TO clause of the statement.
ALTER TABLE mytable RENAME TO new_table_name;
Our exercises use an implementation that only support adding new columns, so give that a try below.