10 Questions
In PL/SQL, can you declare two variables with the same name in the same block?
No, you cannot declare two variables with the same name in the same block.
Why can you declare variables with the same name in two different blocks in PL/SQL?
To allow for nested blocks and maintain variable scope.
What happens if you use the same variable name in two different blocks in PL/SQL?
The variable in the inner block will override the one in the outer block.
In which scenario are variables with the same name distinct in PL/SQL?
When they are declared in two different blocks, one nested within the other.
What is a common naming convention for variables in nested blocks to avoid confusion?
'v_' prefix for all variables.
Why might it not be recommended to declare variables with the same name in nested blocks?
It can cause confusion and make code modification challenging.
What is the consequence of modifying a variable in an inner block that shares its name with an outer block variable?
Changes made to the inner block variable do not affect the outer block variable.
How can declaring variables with the same name in nested blocks impact code readability?
It can introduce confusion and make it harder to understand variable usage.
What is a recommended practice when dealing with variables in nested blocks to avoid scope-related issues?
Prefix variables based on their respective block level (e.g., inner_ and outer_).
What should developers consider when deciding whether to reuse variable names across nested blocks?
Consistency with company coding standards.
Study Notes
Nested Blocks
- Nested blocks are blocks of code placed within other blocks of code, with an outer block and an inner block.
- There is no practical limit to the depth of nesting in Oracle PL/SQL.
Nested Block Example
- The example has an outer (parent) block and a nested (child) block.
- Variables can be declared in both the outer and inner blocks.
- The outer block has access to its own variables and those of the inner block, but the inner block only has access to its own variables.
Benefits of Nested Blocks
- Breaking down large, complex blocks into smaller, nested blocks makes the code easier to read and correct.
- Declared variables might not be available depending on their scope and visibility, but block labels can be used to make them available.
Key Concepts
- PL/SQL is a block-structured language.
- The basic units (procedures, functions, and anonymous blocks) are logical blocks, which can contain any number of nested sub-blocks.
- Each logical block corresponds to a problem to be solved.
Objectives
- Understand the scope and visibility of variables.
- Write nested blocks and qualify variables with labels.
- Describe the rules for variable scope when a variable is nested in a block.
- Recognize a variable scope issue when a variable is used in nested blocks.
- Qualify a variable nested in a block with a label.
Learn about nested blocks in PL/SQL, where code blocks are placed within other blocks. Understand the concept of outer and inner blocks, and how blocks can be nested multiple times without a practical limit. Explore an example of nested blocks in Oracle's PL/SQL.
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