Data Definition Language (DDL) statements provide programmers with a way to redefine the definition of one or more existing tables (see section 6.2).

As one or more new columns are added to a table, each is automatically added at the end of a table’s descriptor record (see section 6.2.1).

To add one or more columns in a designated order, the SQL standard provides a couple of choices to choose from (see section 6.2.2).

PROC SQL enables a character column (but not a numeric column) to have its length changed (see section 6.2.3).

A column’s format and label information can be modified with a MODIFY clause (see sections 6.2.4 and 6.2.5).

The RENAME= SAS data set option must be used in a FROM clause to rename column names (see section 6.2.6).

The DATASETS procedure is the recommended way to rename tables (see section 6.2.7).

An index consists of one or more columns used to uniquely identify each row within a table (see section 6.3).

Column values in existing rows in a table can be modified with the UPDATE statement (see section 6.4).