Book excerpt: Designed as a companion volume to the INFORMIX Guide to SQL: Tutorial, this comprehensive reference covers the Structured Query Language (SQL) as it is implemented in Informix products. KEY TOPICS: Outlines the structure and contents of the demonstration database (stores5) and explains the 21 Informix system catalog tables that describe that structure; defines the column data types supported by Informix products and explains data type conversion techniques; describes the various environment variables that can or should be set to properly use Informix products; explains error handling, the system descriptor area and the SQL Descriptor Area (sqlda); details the workings of all the SQL statements supported by Informix products with step-by-step diagrams explaining every clause of each SQL statement; and shows how to create and use stored procedures. MARKET: A reference to SQL for those who already know how to use computers and who rely on them in their daily work.