In Oracle SQL, conditions are used to specify criteria that determine which rows are included or excluded from the result set of a query. Conditions are typically specified in the WHERE clause of a SELECT statement, and they define the rules for filtering data. Here’s a brief description of conditions in Oracle SQL:

1. Purpose:

• Conditions are used to filter data based on specific criteria, allowing you to retrieve only the rows that meet those criteria. They enable you to perform logical comparisons and tests on columns in the database.

2. Syntax:

• Conditions are typically specified in the WHERE clause of a SELECT statement. The basic syntax for a condition is as follows:SELECT column1, column2, ... FROM table_name WHERE condition;
• The condition can be a combination of one or more expressions, operators, and logical connectors (e.g., AND, OR, NOT).

3. Operators:

• Conditions commonly involve comparison operators, which are used to compare values. Common comparison operators in Oracle SQL include:
  • =: Equal to
  • != or <>: Not equal to
  • >: Greater than
  • <: Less than
  • >=: Greater than or equal to
  • <=: Less than or equal to
• Additionally, other operators like LIKE, BETWEEN, IN, and IS NULL are used for more complex conditions.

4. Logical Connectors:

• Logical connectors such as AND, OR, and NOT are used to combine multiple conditions to create more complex criteria.
• AND: Requires all conditions to be true for a row to be included in the result.
• OR: Requires at least one condition to be true for a row to be included in the result.
• NOT: Negates a condition, meaning it selects rows where the condition is false.

5. Use Cases:

• Conditions are used in various scenarios, including:
  • Filtering rows to retrieve specific subsets of data.
  • Specifying criteria for joining tables in a query.
  • Implementing business rules and constraints in data retrieval.
  • Performing data validation and cleansing.

6. Example:

• For example, to retrieve all employees with a salary greater than 50,000:SELECT employee_name, salary FROM employees WHERE salary > 50000;

7. Performance Considerations:

• Proper indexing, optimization, and careful use of conditions are important for query performance. Complex conditions or inefficient queries can impact performance negatively.

Conditions are a fundamental part of SQL queries in Oracle and play a critical role in data retrieval and manipulation. They allow you to specify the criteria that determine which rows are included in the result set, making it possible to extract specific information from the database based on your requirements.