# `Selecto.Advanced.CaseExpression`

CASE expression support for PostgreSQL conditional logic.

Provides comprehensive support for both simple and searched CASE expressions,
enabling conditional data transformation within SELECT clauses.

## Examples

    # Simple CASE expression
    selecto
    |> Selecto.select([
        "film.title",
        {:case, "film.rating",
          when: [
            {"G", "General Audience"},
            {"PG", "Parental Guidance"},
            {"PG-13", "Parents Strongly Cautioned"},
            {"R", "Restricted"}
          ],
          else: "Not Rated",
          as: "rating_description"
        }
      ])
    
    # Searched CASE expression
    selecto
    |> Selecto.select([
        "customer.first_name",
        {:case_when, [
            {[{"payment_total", {:>, 100}}], "Premium"},
            {[{"payment_total", {:between, 50, 100}}], "Standard"},
            {[{"payment_total", {:>, 0}}], "Basic"}
          ],
          else: "No Purchases",
          as: "customer_tier"
        }
      ])

# `create_searched_case`

Create a searched CASE expression specification.

## Parameters

- `when_clauses` - List of {conditions, result} tuples
- `opts` - Options including :else, :as

## Examples

    # Searched CASE with multiple conditions
    CaseExpression.create_searched_case([
      {[{"payment_total", {:>, 100}}], "Premium"},
      {[{"payment_total", {:between, 50, 100}}], "Standard"},
      {[{"payment_total", {:>, 0}}], "Basic"}
    ], else: "No Purchases", as: "customer_tier")

# `create_simple_case`

Create a simple CASE expression specification.

## Parameters

- `column` - Column to test against
- `when_clauses` - List of {value, result} tuples
- `opts` - Options including :else, :as

## Examples

    # Simple CASE with alias
    CaseExpression.create_simple_case("film.rating", [
      {"G", "General Audience"},
      {"PG", "Parental Guidance"},
      {"R", "Restricted"}
    ], else: "Not Rated", as: "rating_description")

# `validate_case`

Validate a CASE expression specification.

Ensures the CASE expression structure is valid and all conditions are properly formed.

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*Consult [api-reference.md](api-reference.md) for complete listing*