Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_30015 ( "Province" text, "Provincial capital" text, "Commandery" text, "Commandery capital" text, "No. of counties" real )

### Question ###
when changsha is the commandery what is the commandery capital?

### Accurate SQL ###

SELECT "Commandery capital" FROM table_30015 WHERE "Commandery" = 'Changsha 長沙'