Solve the following sql problem:
Among the crimes in all the districts in Chicago, what is the percentage of them happening in the Central district?

Schema:
SCHEMA:
- Table: Community_Area
  - Column: community_area_no
    - Samples: [1, 2, 3, 4, 5]
  - Column: community_area_name
    - Samples: [Rogers Park, West Ridge, Uptown, Lincoln Square, North Center]
  - Column: side
    - Samples: [Far North , Far North , Far North , Far North , North ]
  - Column: population
    - Samples: [54,991, 71,942, 56,362, 39,493, 31,867]
- Table: District
  - Column: district_no
    - Samples: [1, 2, 3, 4, 5]
  - Column: district_name
    - Samples: [Central, Wentworth, Grand Crossing, South Chicago, Calumet]
  - Column: address
    - Samples: [1718 South State Street, 5101 South Wentworh Avenue, 7040 South Cottage Grove Ave, 2255 East 103rd St, 727 East 111th St]
  - Column: zip_code
    - Samples: [60616, 60609, 60637, 60617, 60628]
  - Column: commander
    - Samples: [Jake M. Alderden, Joshua Wallace, Eve T. Quarterman, Robert A. Rubio, Glenn White]
  - Column: email
    - Samples: [ CAPS001District@chicagopolice.org,  CAPS002District@chicagopolice.org,  CAPS003District@chicagopolice.org,  caps.004district@chicagopolice.org,  CAPS005District@chicagopolice.org]
  - Column: phone
    - Samples: [312-745-4290, 312-747-8366, 312-747-8201, 312-747-8205, 312-747-8210]
  - Column: fax
    - Samples: [312-745-3694, 312-747-5396, 312-747-5479, 312-747-4559, 312-747-5935]
  - Column: tty
    - Samples: [312-745-3693, 312-747-6656, 312-747-9168, 312-747-9169, 312-747-9170]
  - Column: twitter
    - Samples: [ ChicagoCAPS01,  ChicagoCAPS02,  ChicagoCAPS03,  ChicagoCAPS04,  ChicagoCAPS05]
- Table: FBI_Code
  - Column: fbi_code_no
    - Samples: [01A, 01B, 2, 3, 04A]
  - Column: title
    - Samples: [Homicide 1st & 2nd Degree, Involuntary Manslaughter, Criminal Sexual Assault, Robbery, Aggravated Assault]
  - Column: description
    - Samples: [The killing of one human being by another., The killing of another person through negligence., Any sexual act directed against another person, forcibly and/or agains..., The taking or attempting to take anything of value under confrontation..., An unlawful attack by one person upon another wherein the offender dis... (truncated)]
  - Column: crime_against
    - Samples: [Persons, Persons, Persons, Property, Persons]
- Table: IUCR
  - Column: iucr_no
    - Samples: [110, 130, 141, 142, 261]
  - Column: primary_description
    - Samples: [HOMICIDE, HOMICIDE, HOMICIDE, HOMICIDE, CRIM SEXUAL ASSAULT]
  - Column: secondary_description
    - Samples: [FIRST DEGREE MURDER, SECOND DEGREE MURDER, INVOLUNTARY MANSLAUGHTER, RECKLESS HOMICIDE, AGGRAVATED: HANDGUN]
  - Column: index_code
    - Samples: [I, I, N, N, I]
- Table: Neighborhood
  - Column: neighborhood_name
    - Samples: [Albany Park, Altgeld Gardens, Andersonville, Archer Heights, Armour Square]
  - Column: community_area_no
    - Samples: [14, 54, 77, 57, 34]
- Table: Ward
  - Column: ward_no
    - Samples: [1, 2, 3, 4, 5]
  - Column: alderman_first_name
    - Samples: [Daniel, Brian, Pat, Sophia, Leslie]
  - Column: alderman_last_name
    - Samples: [La Spata, Hopkins, Dowell, King, Hairston]
  - Column: alderman_name_suffix
    - Samples: [None, None, None, None, None]
  - Column: ward_office_address
    - Samples: [1958 N. Milwaukee Ave., 1400 N. Ashland, 5046 S. State St., 435 E. 35th Street, 2325 E. 71st Street]
  - Column: ward_office_zip
    - Samples: [60647, 60622, 60609, 60616, 60649]
  - Column: ward_email
    - Samples: [info@the1stward.com, ward02@cityofchicago.org, ward03@cityofchicago.org, ward04@cityofchicago.org, ward05@cityofchicago.org]
  - Column: ward_office_phone
    - Samples: [872.206.2685, 312.643.2299, 773.373.9273, 773.536.8103, 773.324.5555]
  - Column: ward_office_fax
    - Samples: [312.448.8829, None, None, 773.536.7296, 773.324.1585]
  - Column: city_hall_office_room
    - Samples: [200, 200, 200, 305, 300]
  - Column: city_hall_office_phone
    - Samples: [None, 312.744.6836, 312.744.8734, 312.744.2690, 312.744.6832]
  - Column: city_hall_office_fax
    - Samples: [None, None, 312.744.6712, 312.744.7738, 312.744.3195]
  - Column: Population
    - Samples: [56149, 55805, 53039, 54589, 51455]
- Table: Crime
  - Column: report_no
    - Samples: [23757, 23758, 23759, 23761, 23762]
  - Column: case_number
    - Samples: [JB100159, JB100522, JB100839, JB101043, JB105277]
  - Column: date
    - Samples: [1/1/2018 2:46, 1/1/2018 11:33, 1/1/2018 18:27, 1/1/2018 22:40, 1/6/2018 12:54]
  - Column: block
    - Samples: [039XX W CORNELIA AVE, 026XX N HAMPDEN CT, 047XX S PRINCETON AVE, 081XX S STONY ISLAND AVE, 015XX E 62ND ST]
  - Column: iucr_no
    - Samples: [110, 110, 110, 110, 110]
  - Column: location_description
    - Samples: [AUTO, APARTMENT, AUTO, ALLEY, STREET]
  - Column: arrest
    - Samples: [FALSE, FALSE, FALSE, TRUE, FALSE]
  - Column: domestic
    - Samples: [FALSE, FALSE, FALSE, FALSE, FALSE]
  - Column: beat
    - Samples: [1732, 1935, 935, 411, 314]
  - Column: district_no
    - Samples: [17, 19, 9, 4, 3]
  - Column: ward_no
    - Samples: [30, 43, 3, 8, 5]
  - Column: community_area_no
    - Samples: [21, 7, 37, 45, 42]
  - Column: fbi_code_no
    - Samples: [01A, 01A, 01A, 01A, 01A]
  - Column: latitude
    - Samples: [41.94456125, 41.92972657, 41.808168, 41.74698404, 41.78289015]
  - Column: longitude
    - Samples: [-87.72668181, -87.64092074, -87.63333646, -87.5854287, -87.58877343]

SELECT CAST(SUM(CASE WHEN T2.district_name = 'Central' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.case_number) FROM Crime AS T1 INNER JOIN District AS T2 ON T1.district_no = T2.district_no