What is the Year Commissioned of the power stationo with a Gross head of less than 18?
CREATE TABLE table_name_58 (year_commissioned INTEGER, gross_head__metres_ INTEGER)
SELECT AVG(year_commissioned) FROM table_name_58 WHERE gross_head__metres_ < 18
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_name_58 (year_commissioned INTEGER, gross_head__metres_ INTEGER) Question: What is the Year Commissioned of the power stationo with a Gross head of less than 18? [/INST] SELECT AVG(year_commissioned) FROM table_name_58 WHERE gross_head__metres_ < 18 </s>