WHERE_IN query with a composite key?

Question

Let\'s say I have a table with a two-part composite key, and 4 records, like the following:

KEY_PART_1 KEY_PART_2
A          1
B          1
C          2
C            


        

Answer 1

This syntax works for Oracle and PostgreSQL:

SELECT *
  FROM table_name
 WHERE (key_part_1, key_part_2) IN ( ('B',1), ('C',2) );

Answer 2

I'm not sure but I think you want something like this which works for almost all RDBMSs:

select KEY_PART_1, KEY_PART_2 from your_table where KEY_PART_1='B' and KEY_PART_2 = '1'
UNION
select KEY_PART_1, KEY_PART_2 from your_table where KEY_PART_1='C' and KEY_PART_2 = '2'

Answer 3

Following @Justin Cave's answer, here is a small test case to show that Oracle would do an INDEX RANGE SCAN followed by an INLIST ITERATOR for the following filter predicate:

WHERE (key_part_1, key_part_2) IN ( ('B',1), ('C',2) )

Setup

SQL> CREATE TABLE t(key1 VARCHAR2(1), key2 NUMBER);

Table created.

SQL>
SQL> INSERT INTO t VALUES('A', 1);

1 row created.

SQL> INSERT INTO t VALUES('B', 1);

1 row created.

SQL> INSERT INTO t VALUES('C', 2);

1 row created.

SQL> INSERT INTO t VALUES('C', 3);

1 row created.

SQL>
SQL> COMMIT;

Commit complete.

SQL>

A composite index on key1 and key2:

SQL> CREATE INDEX t_idx ON t(key1, key2);

Index created.

SQL>

Gather stats:

SQL> EXEC DBMS_STATS.gather_table_stats('LALIT', 'T');

PL/SQL procedure successfully completed.

SQL>

Execute the query:

SQL> SELECT * FROM t
  2  WHERE (key1, key2) IN ( ('B',1), ('C',2) );

K       KEY2
- ----------
B          1
C          2

SQL>

So, it gives the correct output.

Let's see the explain plan:

Case# 1 Key-value pair in the same order of the index. Leading key in the lead.

SQL> SELECT * FROM TABLE(dbms_xplan.display);

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2301620486

---------------------------------------------------------------------------
| Id  | Operation         | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |       |     2 |    10 |     1   (0)| 00:00:01 |
|   1 |  INLIST ITERATOR  |       |       |       |            |          |
|*  2 |   INDEX RANGE SCAN| T_IDX |     2 |    10 |     1   (0)| 00:00:01 |
---------------------------------------------------------------------------

Predicate Information (identified by operation id):

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
---------------------------------------------------

   2 - access(("KEY1"='B' AND "KEY2"=1 OR "KEY1"='C' AND "KEY2"=2))

14 rows selected.

Case# 2 Key-value pair in opposite order of the index. Leading key in reverse.

SQL> EXPLAIN PLAN FOR SELECT * FROM t
  2  WHERE (key2, key1) IN ( (1, 'B'), (2, 'C') );

Explained.

SQL>
SQL> SELECT * FROM TABLE(dbms_xplan.display);

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2301620486

---------------------------------------------------------------------------
| Id  | Operation         | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |       |     2 |    10 |     1   (0)| 00:00:01 |
|   1 |  INLIST ITERATOR  |       |       |       |            |          |
|*  2 |   INDEX RANGE SCAN| T_IDX |     2 |    10 |     1   (0)| 00:00:01 |
---------------------------------------------------------------------------

Predicate Information (identified by operation id):

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
---------------------------------------------------

   2 - access(("KEY1"='B' AND "KEY2"=1 OR "KEY1"='C' AND "KEY2"=2))

14 rows selected.

In either cases, Oracle uses the index.