UPPER(string_expression)
LOWER(string_expression)
TRIM([LEADING | TRAILING | BOTH] [characters FROM] string_expression)
LENGTH(string_expression)
REPLACE(string_expression, search_string, replacement_string)

SELECT 
    customer_name,
    UPPER(customer_name) as name_uppercase,
    LOWER(customer_name) as name_lowercase,
    UPPER(email) as email_uppercase,
    LOWER(email) as email_lowercase,
    -- Proper case (first letter uppercase)
    CONCAT(
        UPPER(SUBSTRING(customer_name, 1, 1)),
        LOWER(SUBSTRING(customer_name, 2))
    ) as name_proper_case
FROM

SELECT 
    product_code,
    LENGTH(product_code) as original_length,
    TRIM(product_code) as trimmed,
    LENGTH(TRIM(product_code)) as trimmed_length,
    -- Remove specific characters
    TRIM(BOTH '-' FROM product_code) as trim_dashes,
    -- Left trim only
    LTRIM(product_code) as left_trimmed,
    -- Right trim only
    RTRIM(product_code) as right_trimmed
FROM

SELECT 
    description,
    LENGTH(description) as char_count,
    LENGTH(TRIM(description)) as char_count_trimmed,
    -- Check for empty or whitespace-only strings
    CASE 
        WHEN LENGTH(TRIM(description)) = 0 THEN 'Empty'
        WHEN LENGTH(TRIM(description)) < 10 THEN 'Short'
        WHEN LENGTH(TRIM(description)) < 50 THEN 'Medium'
        ELSE 'Long'
    END as description_length_category,
    -- Truncate long descriptions
    CASE 
        WHEN LENGTH(description) > 50 
        THEN SUBSTRING(description, 1, 47) || '...'
        ELSE description
    END as truncated_description
FROM

SELECT 
    phone_number,
    -- Remove formatting characters
    REPLACE(REPLACE(REPLACE(phone_number, '(', ''), ')', ''), '-', '') as clean_phone,
    -- Standardize format
    REPLACE(REPLACE(phone_number, '.', '-'), '/', '-') as standardized_phone,
    -- Mask sensitive data
    CONCAT(
        SUBSTRING(phone_number, 1, 3),
        REPLACE(SUBSTRING(phone_number, 4), SUBSTRING(phone_number, 4, LENGTH(phone_number) - 6), 'XXX')
    ) as masked_phone
FROM

SELECT 
    customer_name_raw,
    -- Clean and standardize name
    TRIM(
        UPPER(
            REPLACE(
                REPLACE(
                    REPLACE(customer_name_raw, '  ', ' '),  -- Double spaces to single
                    ',', ''),  -- Remove commas
                '.', '')  -- Remove periods
        )
    ) as customer_name_clean,
    
    email_raw,
    -- Clean and standardize email
    LOWER(TRIM(email_raw)) as email_clean,
    
    -- Validate email format (basic check)
    CASE 
        WHEN LOWER(TRIM(email_raw)) LIKE '%@%.%' 
        AND LENGTH(TRIM(email_raw)) > 5
        THEN 'Valid'
        ELSE 'Invalid'
    END as email_status
FROM

SELECT 
    product_name,
    -- Create SKU from product name
    CONCAT(
        UPPER(SUBSTRING(REPLACE(TRIM(product_name), ' ', ''), 1, 3)),
        '-',
        LPAD(CAST(product_id AS VARCHAR), 5, '0')
    ) as generated_sku,
    
    -- Clean description
    CASE 
        WHEN LENGTH(TRIM(description)) > 0 THEN
            CONCAT(
                UPPER(SUBSTRING(TRIM(description), 1, 1)),
                LOWER(SUBSTRING(TRIM(description), 2))
            )
        ELSE 'No description'
    END as clean_description,
    
    -- Category standardization
    UPPER(REPLACE(TRIM(category), '_', ' ')) as category_standardized
FROM

LOWER(TRIM(email)) as

REGEXP_REPLACE(text, '\s+', ' ')  -- Replace multiple whitespace with single space

REPLACE(REPLACE(REPLACE(REPLACE(phone, '(', ''), ')', ''), '-', ''), ' ', '')

-- Platform-specific, or use INITCAP in some platforms
CONCAT(
    UPPER(SUBSTRING(word, 1, 1)),
    LOWER(SUBSTRING(word, 2))
)