Checking multiple columns using "IN"

Question

I have a query
select 1 from tableA
where
cond1 = val1 and
exists
( col1, col2, col3, col4 ) IN
( select
     cola, colb, colc, cold
from
     table B
where
     cond1 = val1
Will this condition Checking for multiple columns in the IN work ?
I actually mispelled a column name ( say colb ) in the sub query but it did not give a error, but executed fine by matching part of the columns alone?

Answer 1

The execution plans look strangely similar.
SQL> CREATE TABLE t1 (c1 INT NOT NULL, c2 INT NOT NULL, c3 INT NOT NULL);
Table created.
SQL> INSERT INTO t1 (c1,c2,c3)
  2  SELECT dbms_random.value(0,9)
  3       , dbms_random.value(0,99)
  4       , dbms_random.value(0,999)
  5  FROM   dual CONNECT BY LEVEL <= 10000;
10000 rows created.
SQL> CREATE TABLE t2 AS SELECT * FROM t1 SAMPLE BLOCK(10);
Table created.
SQL> BEGIN
  2      DBMS_STATS.GATHER_TABLE_STATS(user,'T1');
  3      DBMS_STATS.GATHER_TABLE_STATS(user,'T2');
  4  END;
  5  /
PL/SQL procedure successfully completed.
SQL> SELECT * FROM t1 WHERE (c1,c2,c3) IN
  2         ( SELECT c1,c2,c3 FROM t2 )
  3 
SQL> @xplan
Plan hash value: 1275841967
| Id  | Operation            | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT     |      |     1 |    18 |    12   (9)| 00:00:01 |
|*  1 |  HASH JOIN RIGHT SEMI|      |     1 |    18 |    12   (9)| 00:00:01 |
|   2 |   TABLE ACCESS FULL  | T2   |   209 |  1881 |     3   (0)| 00:00:01 |
|   3 |   TABLE ACCESS FULL  | T1   | 10000 | 90000 |     8   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   1 - access("C1"="C1" AND "C2"="C2" AND "C3"="C3")
SQL> SELECT * FROM t1 WHERE EXISTS
  2         ( SELECT NULL FROM t2
  3           WHERE  c1 = t1.c1                   
  4           AND    c2 = t1.c2
  5           AND    c3 = t1.c3 )
  6 
SQL> @xplan
Plan hash value: 1275841967
| Id  | Operation            | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT     |      |     1 |    18 |    12   (9)| 00:00:01 |
|*  1 |  HASH JOIN RIGHT SEMI|      |     1 |    18 |    12   (9)| 00:00:01 |
|   2 |   TABLE ACCESS FULL  | T2   |   209 |  1881 |     3   (0)| 00:00:01 |
|   3 |   TABLE ACCESS FULL  | T1   | 10000 | 90000 |     8   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   1 - access("C1"="T1"."C1" AND "C2"="T1"."C2" AND "C3"="T1"."C3")
SQL>