What is the average number for Northgate which commenced its construction before 1951?
CREATE TABLE table_name_42 (number_on_map INTEGER, name VARCHAR, construction_commenced VARCHAR)
SELECT AVG(number_on_map) FROM table_name_42 WHERE name = "northgate" AND construction_commenced < 1951
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_name_42 (number_on_map INTEGER, name VARCHAR, construction_commenced VARCHAR) Question: What is the average number for Northgate which commenced its construction before 1951? [/INST] SELECT AVG(number_on_map) FROM table_name_42 WHERE name = "northgate" AND construction_commenced < 1951 </s>