Operator "LIKE" versus operator "="

Question

I have textual column C in table T, and parameter P.
If parameter P has value "abc"
then is there difference in perfomace between those 2:
"where T.C like P"
"where T.C = P"
Both conditions produce same resultset of the query. But maybe with LIKE operator the query is slower? And you would still suggest to use operator "=" if possible?

Answer 1

>
I don't believe that testing gives the correct answer.
I believe there is a theoretical answer to the question.
>
Why not? Yes, there could be difference in parsing the command, but regarding the execution time, I don't see a difference in my example, do you?
SELECT *
  FROM v$session
WHERE USERNAME = 'ANONYMOUS'
Execution Plan
Plan hash value: 3733760267
| Id  | Operation                | Name            | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT         |                 |     1 |  1064 |     0   (0)| 00:00:01 |
|   1 |  NESTED LOOPS            |                 |     1 |  1064 |     0   (0)| 00:00:01 |
|*  2 |   FIXED TABLE FULL       | X$KSUSE         |     1 |   855 |     0   (0)| 00:00:01 |
|*  3 |   FIXED TABLE FIXED INDEX| X$KSLED (ind:2) |     1 |   209 |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - filter("S"."KSUUDLNA"='ANONYMOUS' AND "S"."INST_ID"=USERENV('INSTANCE') AND
              BITAND("S"."KSSPAFLG",1)<>0 AND BITAND("S"."KSUSEFLG",1)<>0)
   3 - filter("S"."KSUSEOPC"="E"."INDX")
Statistics
          0  recursive calls
          0  db block gets
          0  consistent gets
          0  physical reads
          0  redo size
       6082  bytes sent via SQL*Net to client
        384  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          7  rows processed
SELECT *
  FROM v$session
WHERE USERNAME LIKE 'ANONYMOUS'
Execution Plan
Plan hash value: 3733760267
| Id  | Operation                | Name            | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT         |                 |     1 |  1064 |     0   (0)| 00:00:01 |
|   1 |  NESTED LOOPS            |                 |     1 |  1064 |     0   (0)| 00:00:01 |
|*  2 |   FIXED TABLE FULL       | X$KSUSE         |     1 |   855 |     0   (0)| 00:00:01 |
|*  3 |   FIXED TABLE FIXED INDEX| X$KSLED (ind:2) |     1 |   209 |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - filter("S"."KSUUDLNA" LIKE 'ANONYMOUS' AND "S"."INST_ID"=USERENV('INSTANCE')
              AND BITAND("S"."KSSPAFLG",1)<>0 AND BITAND("S"."KSUSEFLG",1)<>0)
   3 - filter("S"."KSUSEOPC"="E"."INDX")
Statistics
          8  recursive calls
          0  db block gets
          2  consistent gets
          0  physical reads
          0  redo size
       6082  bytes sent via SQL*Net to client
        384  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          7  rows processedC.