CREATE TABLE table_149426_4 (prefix_size VARCHAR2, network_mask VARCHAR2)

When the network mask is 255.255.255.252 what is the prefix size?
SELECT prefix_size FROM table_149426_4 WHERE network_mask = "255.255.255.252"
SELECT "prefix_size" FROM "table_149426_4" WHERE "255.255.255.252" = "network_mask"