What is the difference between "where" and "having" in SQL?

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The Fundamental Difference

1. WHERE Clause:

• Definition:
  • The "WHERE" clause is used in SQL to filter rows based on specified conditions.
• Application:
  • Applied to individual rows before they are grouped or aggregated.

2. HAVING Clause:

• Definition:
  • The "HAVING" clause is used to filter the results of aggregate functions applied to groups created by the "GROUP BY" clause.
• Application:
  • Applied to the result set after grouping, allowing conditions on aggregated values.

Key Distinctions

1. Application Scope:

• WHERE Clause:
  • Applied to individual rows before grouping.
  • Filters data based on conditions specified for each row.
• HAVING Clause:
  • Applied to grouped results.
  • Filters results based on conditions applied to aggregated values.

2. Usage with Aggregate Functions:

• WHERE Clause:
  • Typically used with non-aggregated columns.
  • Filters data before any aggregation occurs.
• HAVING Clause:
  • Used with aggregate functions like COUNT, SUM, AVG.
  • Allows filtering based on results of these aggregate functions.

3. Syntax and Placement:

• WHERE Clause:
  • Appears before the "GROUP BY" clause in queries involving grouping.
• HAVING Clause:
  • Appears after the "GROUP BY" clause in queries involving grouping.

Use Cases and Examples

1. Example Using WHERE Clause:

• Retrieves rows where the value in "column3" is greater than 100.

2. Example Using HAVING Clause: