Table: superconductors
Columns: formula
notation
t_c_k
no_of_cu_o_planes_in_unit_cell
crystal_structure

Question: What is the notion when the crystal structure is tetragonal and the formula is bi 2 sr 2 cacu 2 o 8
SQL: SELECT "notation" FROM superconductors WHERE "crystal_structure" = 'Tetragonal' AND "formula" = 'Bi 2 Sr 2 CaCu 2 O 8'

Question: How many times is the formula tl 2 ba 2 cuo 6?
SQL: SELECT "no_of_cu_o_planes_in_unit_cell" FROM superconductors WHERE "formula" = 'Tl 2 Ba 2 CuO 6'

Question: What is the crystal structure for the formula yba 2 cu 3 o 7?
SQL: SELECT "crystal_structure" FROM superconductors WHERE "formula" = 'YBa 2 Cu 3 O 7'

Question: What is the number for t c (k) when the notation is tl-2212?
SQL: SELECT COUNT("t_c_k") FROM superconductors WHERE "notation" = 'Tl-2212'