the-biergarten-app/archive/sql-stored-procs-functions/03-crud/04-Location/USP_CreateCity.sql

CREATE OR ALTER PROCEDURE dbo.USP_CreateCity(
    @CityName NVARCHAR(100),
    @StateProvinceCode NVARCHAR(6)
)
AS
BEGIN
    SET
        NOCOUNT ON;
    SET
        XACT_ABORT ON;

    BEGIN
        TRANSACTION
        DECLARE
            @StateProvinceId UNIQUEIDENTIFIER = dbo.UDF_GetStateProvinceIdByCode(@StateProvinceCode);
        IF
            @StateProvinceId IS NULL
            BEGIN
                THROW
                    50001, 'State/province does not exist', 1;
            END

        IF
            EXISTS (SELECT 1
                    FROM dbo.City
                    WHERE CityName = @CityName
                      AND StateProvinceID = @StateProvinceId)
            BEGIN

                THROW
                    50002, 'City already exists.', 1;
            END

        INSERT INTO dbo.City
            (StateProvinceID, CityName)
        VALUES (@StateProvinceId, @CityName);
    COMMIT TRANSACTION
END;