How WooCommerce Coupons are stored in Database?

WooCommerce Coupon are stored in wp_posts table with post_type => 'shop_coupon'. And all the associated data are stored in wp_postmeta table.

You can use this MySQL query to get all the Coupon:

SELECT * FROM `wp_posts` WHERE `post_type` = 'shop_coupon' ORDER BY `ID` DESC

And this gets all coupons

SELECT p.`ID`,        p.`post_title`   AS coupon_code,        p.`post_excerpt` AS coupon_description,        Max(CASE WHEN pm.meta_key = 'discount_type'      AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS discount_type,          -- Discount type        Max(CASE WHEN pm.meta_key = 'coupon_amount'      AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS coupon_amount,          -- Coupon amount        Max(CASE WHEN pm.meta_key = 'free_shipping'      AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS free_shipping,          -- Allow free shipping        Max(CASE WHEN pm.meta_key = 'expiry_date'        AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS expiry_date,                -- Coupon expiry date        Max(CASE WHEN pm.meta_key = 'minimum_amount'     AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS minimum_amount,         -- Minimum spend        Max(CASE WHEN pm.meta_key = 'maximum_amount'     AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS maximum_amount,         -- Maximum spend        Max(CASE WHEN pm.meta_key = 'individual_use'     AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS individual_use,         -- Individual use only        Max(CASE WHEN pm.meta_key = 'exclude_sale_items' AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS exclude_sale_items,         -- Exclude sale items        Max(CASE WHEN pm.meta_key = 'product_ids'    AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS product_ids,                -- Products        Max(CASE WHEN pm.meta_key = 'exclude_product_ids'AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS exclude_product_ids,        -- Exclude products        Max(CASE WHEN pm.meta_key = 'product_categories' AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS product_categories,             -- Product categories        Max(CASE WHEN pm.meta_key = 'exclude_product_categories' AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS exclude_product_categories,-- Exclude Product categories        Max(CASE WHEN pm.meta_key = 'customer_email'     AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS customer_email,         -- Email restrictions        Max(CASE WHEN pm.meta_key = 'usage_limit'    AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS usage_limit,                -- Usage limit per coupon        Max(CASE WHEN pm.meta_key = 'usage_limit_per_user'   AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS usage_limit_per_user,   -- Usage limit per user        Max(CASE WHEN pm.meta_key = 'usage_count'    AND  p.`ID` = pm.`post_id` THEN pm.`meta_value` END) AS total_usaged                   -- Usage count FROM   `wp_posts` AS p        INNER JOIN `wp_postmeta` AS pm ON  p.`ID` = pm.`post_id` WHERE  p.`post_type` = 'shop_coupon'        AND p.`post_status` = 'publish' GROUP  BY p.`ID` ORDER  BY p.`ID` ASC;

Reference: MySQL Query to Get All Coupon