Database: yelp
Question: How many users have reviewed Irish Pub in Dallas ?
SQL:
SELECT COUNT ( DISTINCT t4.name ) FROM category AS t2 JOIN business AS t1 ON t2.business_id  =  t1.business_id JOIN review AS t3 ON t3.business_id  =  t1.business_id JOIN USER AS t4 ON t4.user_id  =  t3.user_id WHERE t1.city  =  "Dallas" AND t2.category_name  =  "Irish Pub";