9.1. DECODE, NULLIF, NVL, and NVL29.1.1. DECODE9.1.2. NULLIF9.1.3. NVL and NVL29.2. The Case for CASE9.2.1. Searched CASE Expressions9.2.2. Simple CASE Expressions9.3. DECODE and CASE Examples9.3.1. Result Set Transformations9.3.2. Selective Function Execution9.3.3. Conditional Update9.3.4. Optional Update9.3.5. Selective Aggregation9.3.6. Checking for Existence9.3.7. Division by Zero Errors9.3.8. State Transitions