Oracle 9i Fundamentals I Exam Cram™ 2 (Exam 1Z0-031)

Structure of a Row

Everything in the database has a structure; rows are no exception. Row data is stored within database blocks as records of varying lengths. The columns in a row are stored in the order in which they are defined in the table, and any NULL columns that are trailing columns are not stored.

Nontrailing NULL columns require a single byte of storage for each column length.

Each row in any table may therefore have a different number of columns depending on where NULL values occur. Each row in a table, however, has a row header and row data. The row header stores the number of columns in the row, any row chaining information that may ...