s$="abcdefghijk",left$(s$,4)的值是()。
A、“efghijk”
B、“hijk”
C、“abcd”
D、abcdefg
A、“efghijk”
B、“hijk”
C、“abcd”
D、abcdefg
A、select s.s#,sname from s where s.s#=(selectsc.s#fromscwherec#=’c2’ B、select s.s#,sname from s,s cwhere s.s#=sc.s#andc#=’c2’ C、select s.s#,sname from s joinscon s.s#=sc.s#wherec#=’c2’ D、select s.s#,sname from s where s.s#in(selectsc.s#fromscwherec#=’c2’)
A、E(S)=C(S)·H(S) B、E(S)=R(S)·C(S)·H(S) C、E(S)=R(S)·H(S)-C(S) D、E(S)=R(S)-C(S·)H(S)
A、A、2Mb/s,8Mb/s,34Mb/s,140Mb/s B、B、1.5Mb/s,6.3Mb/s,45Mb/s,274Mb/s C、C、155Mb/s,622Mb/s,2.5Gb/s,10Gb/s D、D、52Mb/s,155Mb/s,466Gb/s,622Mb/s……10Gb/s
A、A.E(S)=R(S)×G(S) B、B.E(S)=R(S)×G(S)×H(S0 C、C.E(S)=R(S)-G(S)H(S)