user: Question: Name the number of vocalists for  Which One ~ Is It?
Columns: ['#', 'Japanese title', 'Rōmaji', 'Japanese translation', 'Vocalist', 'Episodes used']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '君のそばで～ヒカリのテーマ～', 'Kimi no Soba de ~Hikari no Tēma~', "By Your Side ~Hikari's Theme~", 'Grin', 'DP001 - DP024']
SQL:

assistant: SELECT COUNT("Vocalist") FROM "Table" WHERE "Japanese translation" = 'Which One ~ Is It?';