Contents Index Reduce primary key width Use appropriate data types

ASA SQL User's Guide
  Monitoring and Improving Performance
    Top performance tips

Declare constraints

Undeclared primary key-foreign key relationships exist between tables when there is an implied relationship between the values of columns in different tables. It is true that not declaring the relationship can save time on index maintenance, however, declaring the relationship can improve performance of queries when joins take place because the cost model is able to do a better job of estimation.

Contents Index Reduce primary key width Use appropriate data types