CREATE TABLE table_51963 ("Train No." TEXT, "Train Name" TEXT, "Origin" TEXT, "Destination" TEXT, "Frequency" TEXT)

What is the frequency of the Chennai Egmore Dibrugarh Express to Dibrugarh?
SELECT "Frequency" FROM table_51963 WHERE "Destination" = 'dibrugarh' AND "Train Name" = 'chennai egmore dibrugarh express'
SELECT "Frequency" FROM "table_51963" WHERE "Destination" = 'dibrugarh' AND "Train Name" = 'chennai egmore dibrugarh express'