SAS code troubleshooting

proc sql;
update AcSL
set tt='Y' where tt=1
tt='N' where tt=0

sagety='Y' where sagety=1
sagety='N' where sagety=0

PPt='Y' where PPt=1
PPt='N' where PPt=0

compaete='Y' where compaete=1
compaete='N' where compaete=0;
quit;

Can anyone tell me what wrong with this code?