The Author Craig Mullen presented great ideas, how performance can be improved with DB2 SQL.
Read DB2 questions, if you miss it.
- Always use query with where clause.
- Always create indexes on table.
- Explicit join is performance worth than Inner join.
- Always put exact columns that you want to retrieve in SELECT statement, not more than that.
- Use FETCH FIRST n ROWS ONLY. Take an example FETCH FIRST 1 ROWS ONLY, after returns 1 row, you will receive SQl CODE= +100.
- Use OPTIMIZE FOR n ROWS.
- For read only cursors always use FOR READ ONLY