Chapter 5 - Compression
“If you aren't compressing your Teradata tables, you are simply leaving money on the table.”
- Tera-Tom Coffing
Important Information about Compression
The COMPRESS clause works in two different ways:
- When issued by itself (without a value or values), COMPRESS causes all NULL values for that column to be compressed to zero space. The Presence Bit for Nulls is used so no cost.
- When issued with value (e.g., COMPRESS ‘Ohio’, ‘Iowa’, ‘Georgia’), the COMPRESS clause will compress every occurrence of Ohio, Iowa, and Georgia in that column to zero space as well as cause every NULL value to be compressed. You can compress up to 255 values per column, and the cost is between 1 and 8 bits per row of additional cost.