Question: What is the sum of Year opened when steel was the material with a Span feet of 1476?
SQL: SELECT SUM("Year opened") FROM "2-1549729-2" WHERE "Material" = 'steel' AND "Span feet" = 1476.0;

Question: What is the sum of Year opened when the span feet is more than 1247, and the spam metres is 384?
SQL: SELECT SUM("Year opened") FROM "2-1549729-2" WHERE "Span feet" > 1247.0 AND "Span metres" = 384.0;