Decode is bad to use

Question

Is it true that Decode should be avoided because it makes the query run slow.I am told this constantly in my organization by sql developer.Is it true.

Answer 1

I never use case, because I think it is slower.
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL> create table scott.t11 as select rownum r, trunc(dbms_random.value(1,5)) v
  2 from (select null from dual group by cube(null,null,null,null,null,null,null,null,null,null)),(select null from dual group by cube(null,null,null,null,null,null,null,null,null,null))
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL> exec runstats_pkg.rs_start;
PL/SQL procedure successfully completed.
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL> select sum(decode(v,1,10,2,20,30)) from scott.t11;
SUM(DECODE(V,1,10,2,20,30))
                   23606180
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL> exec runstats_pkg.rs_middle
PL/SQL procedure successfully completed.
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL> select sum(case v when 1 then 10 when 2 then 20 else 30 end) from scott.t11;
SUM(CASEVWHEN1THEN10WHEN2THEN20ELSE30END)
                                 23606180
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL> exec runstats_pkg.rs_stop(500)
Run1 ran in 851 hsecs
Run2 ran in 2709 hsecs
run 1 ran in 31.41% of the time
Name                                  Run1        Run2        Diff
STAT...Elapsed Time                    856       2,713       1,857
STAT...session pga memory           65,536           0     -65,536
Run1 latches total versus runs -- difference and pct
Run1        Run2        Diff       Pct
3,339       5,624       2,285     59.37%
PL/SQL procedure successfully completed.
SYS@LSC63 AS SYSDBA/10.2.0.1
SQL>