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_name_8 ( share INTEGER, air_date VARCHAR, viewers VARCHAR )

### Question ###
What is the lowest share with an air date of March 21, 2008 and had viewers larger than 5.15?

### Accurate SQL ###

SELECT MIN(share) FROM table_name_8 WHERE air_date = "march 21, 2008" AND viewers > 5.15