SELECT 
  COUNT(*) 
FROM 
  cscart_storefronts AS storefronts 
  LEFT JOIN cscart_storefronts_currencies AS currencies ON storefronts.storefront_id = currencies.storefront_id 
WHERE 
  1 = 1 
  AND (
    currencies.currency_id IN ('4')
  )

Query time 0.00010

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Impossible WHERE noticed after reading const tables

Result

COUNT(*)
0