Table:
Rank | Name | Image | Height / ft (m) | Floors | Year | Notes
1 | Key Tower |  | 947 (289) | 57 | 1991 | 104th-tallest building in the world / 20th-tallest building in the United States / Has been the tallest building in the city and state since 1991 / Stood as the tallest building in the United States between New York City and Chicago from its completion until 2007, when Comcast Center in Philadelphia was completed / Tallest building constructed in Cleveland in the 1990s
2 | Terminal Tower |  | 723 (220) | 52 | 1930 | 114th-tallest building in the United States / Stood as the tallest building in the world outside of New York City until 1964 / Tallest building constructed in the city in the 1930s
3 | 200 Public Square |  | 658 (201) | 45 | 1985 | Also known as the BP Building / Tallest building constructed in the city in the 1980s
4 | Tower at Erieview |  | 529 (161) | 40 | 1964 | Tallest building constructed in Cleveland in the 1960s
5 | One Cleveland Center |  | 450 (137) | 31 | 1983 | 
6 | Fifth Third Center |  | 446 (136) | 27 | 1992 | 
7 | Federal Court House Tower |  | 430 (131) | 23 | 2002 | Tallest building constructed in the city in the 2000s / Most recently completed skyscraper in the city
8 | Justice Center Complex |  | 420 (128) | 26 | 1977 | Tallest building constructed in the city in the 1970s
9 | Anthony J. Celebrezze Federal Building |  | 419 (128) | 31 | 1967 | 
10 | PNC Center |  | 410 (125) | 35 | 1980 | Originally known as the National City Center; building was renamed in 2009
11 | AT Tower |  | 390 (119) | 28 | 1971 | Previously known as Cleveland Trust Tower / Currently being redeveloped as a mixed use hotel, retail, and residential building attached to the new Cuyahoga County Headquarters / Also known as 900 Euclid Tower
12 | AT&T Huron Road Building |  | 365 (111) | 24 | 1927 | Commonly known as Ohio Bell Buildinh / Previously known as the Ameritech Building / Tallest building constructed in Cleveland in the 1920s
13 | Rhodes Tower |  | 363 (111) | 20 | 1971 | Originally known as the University Tower
14 | Eaton Center |  | 356 (109) | 28 | 1983 | 
15 | Ernst & Young Tower |  | 330 (101) | 21 | 2013 | Phase I of the Flats East Bank redevelopment project / First downtown private office building constructed since 1992
16 | Marriott at Key Center |  | 320 (98) | 28 | 1991 | Tallest all-hotel building in the city
17 | McDonald Investment Center |  | 308 (94) | 23 | 1968 | Also known as Key Center / Formerly known as the Central National Bank Building
18 | 55 Public Square |  | 300 (91) | 22 | 1958 | Tallest building constructed in the city the 1950s / Originally known as the Illuminating Building
19 | Huntington Bank Building | — | 289 (88) | 21 | 1924 | 
20 | North Point Tower |  | 285 (87) | 20 | 1990 | 
21= | Diamond Building |  | 282 (86) | 23 | 1972 | 
21= | Standard Building |  | 282 (86) | 21 | 1925 | 
23 | 1717 East Ninth Building | — | 275 (84) | 21 | 1959 | Also known as the East Ohio Building
24 | Keith Building |  | 272 (83) | 21 | 1922 | 
25= | East Tower |  | 266 (81) | 25 | 1973 | Tallest all-residential building in the city / Also known as the Reserve Square Apartments
25= | Embassy Suites Tower |  | 266 (81) | 26 | 1969 | Also known as Embassy Suites at Reserve Square
27 | Superior Building |  | 265 (81) | 22 | 1922 | 
28 | Fenn Tower |  | 265 (81) | 21 | 1930 | 
29 | Landmark Office Towers |  | 260 (79) | 22 | 1930 | 
30= | Penton Media Building | — | 253 (77) | 21 | 1972 | 
30= | Ohio Savings Plaza | — | 253 (77) | 17 | 1969 | 
30= | Ameritech Center |  | 253 (77) | 16 | 1983 |

Question: how many buildings have less than 20 floors?
Answer: 2

Question: what is the difference in height between key tower and 55 public square
Answer: 647 feet

Question: how many buildings were built after 1950?
Answer: 24

Question: what is the name of the building with the first downtown private office building constructed since 1992?
Answer: Ernst & Young Tower

Question: which building has the greatest number of floors?
Answer: Key Tower

Question: which building is the tallest?
Answer: Key Tower

Question: when the key tower was built in 1991, what was the previous tallest building constructed?
Answer: Terminal Tower