นักว่ายน้ำในรอบรองชนะเลิศมีสัญชาติอะไรด้วยเวลา 29.51 น. ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
What was the nationality of the swimmer in the semifinal with a time of 29.51?It is not neccessary to use all the tables.
 table_49136:  "Event" [ text]  "Date" [ text]  "Round" [ text]  "Name" [ text]  "Nationality" [ text]  "Time" [ text]  "Record" [ text] 
SELECT "Nationality" FROM table_49136 WHERE "Round" = 'semifinal' AND "Time" = '29.51'