WHERE_IN使用組合鍵查詢？

Question

比方說，我有兩部分的複合鍵的表，和4個記錄，類似如下：

KEY_PART_1 KEY_PART_2 
A   1 
B   1 
C   2 
C   3 

我想寫一些動態SQL只選擇記錄B，1和C 2使用「WHERE IN」子句，沒有選擇A，1或C，3。

有沒有辦法做到這一點，沒有臨時表？

這並不重要，但我們目前正在使用Oracle，並希望儘快遷移到PostgreSQL。

Answer 1

該語法同樣適用於Oracle和PostgreSQL：

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

Answer 2

我不知道，但我想你想是這樣的，其適用於幾乎所有的RDBMS：

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

繼@Justin洞的回答，這裏有一個小測試用例來表明Oracle會做INDEX RANGE SCAN後面跟着INLIST ITERATOR以下過濾謂詞：

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

設置

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> 

上KEY1和KEY2甲綜合指數：

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

Index created. 

SQL> 

收集相關統計數據：

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

PL/SQL procedure successfully completed. 

SQL> 

執行查詢：

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

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

SQL> 

所以，它給正確的輸出。

讓我們來看看解釋計劃：

案例＃1鍵值對索引的順序相同。領先的關鍵。

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. 

情況＃2鍵 - 值對中的索引的順序相反。領先鑰匙反向。

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. 

在任一情況下，Oracle使用索引。