Oracle Magazine, March/April 2019
Database Developer and DBA ETL returned most likely with performance problems associated with processing a large volume of rows For this reason I advocate to developers that they always fully qualify all expressions in a SQL statement with appropriate aliasing In the example above full aliasing would have immediately informed the developer of the wrongcolumn name error in the SQL text as shown in Listing 15 ORACLE MAGAZINE MARCH APRIL 2019 114 Listing 15 Aliased SQL query SQL select s 2 from sales s 3 where s region in 4 select p region 5 from promoted_ locations p 6 where p campaign BLACK FRIDAY ERROR at line 4 ORA 00904 REGION invalid identifier THE LAWS OF PHYSICS Once business requirements are validated and SQL statements have been confirmed as being syntactically and functionally correct theres one more step to take before you start digging into the lower level performance tuning steps Analyze the amount of work the SQL statement must do with the current database design For example if the business requirement is Find the largest single transaction amount the company has ever had
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