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_22900 ( "Series No." real, "Season No." real, "Title" text, "Directed by" text, "Written by" text, "Original air date" text, "U.K. viewers (million)" text )

### Question ###
What's the series number of the episode with season number 2?

### Accurate SQL ###

SELECT MIN("Series No.") FROM table_22900 WHERE "Season No." = '2'