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_23408094_14 (tournament_at_which_lead_began VARCHAR, player VARCHAR)

### Question ###
At what tournament did pete sampras begin his lead?

### Accurate SQL ###

SELECT tournament_at_which_lead_began FROM table_23408094_14 WHERE player = "Pete Sampras"