Table: helmer_trans
Columns: region
start_datum
target_datum
c_x_metre
c_y_metre
c_z_metre
s_ppm
r_x_arcsecond
r_y_arcsecond
r_z_arcsecond

Question: How many values of r z (arcsecond) correspond with a r y (arcsecond) value of −0.247?
SQL: SELECT "r_z_arcsecond" FROM helmer_trans WHERE "r_y_arcsecond" = '−0.247'

Question: How many values of r z(arcsecond) are associated with a target datum of Ireland 1965?
SQL: SELECT "r_z_arcsecond" FROM helmer_trans WHERE "target_datum" = 'Ireland 1965'