SQLÓï¾äPART7
Merge statement
function benefits: 1) provides the ability to conditionally update, insert or delete data into a database table. 2) performs an update if the row exists, and an insert if it is a new row. --> 1) avoids seperate updates, 2) increase performance and ease of use. 3) is useful in data warehousing applications.
syntax:
MERGE INTO table_name table_alias
USING (table|view|sub_query) alias
ON (join condition)
WHEN MATCHED THEN
UPDATE SET
col1 = col1_val,
col2 = col2_val
WHEN NOT MATCHED THEN
INSERT (column_list)
VALUES (column_values);
e.g.: table: temp_t1:
results:
1 1 ÊÕÎÄ SHOUWEN
2 1 ·¢ÎÄ FAWEN
3 1 ½»°ì JIAOBAN
4 2 Öµ°à±¨¸æ REPORT
5 3 ¶½²ì¶½°ì SUPERVISAL
6 2 Öµ°à¿ì±¨ DAILYREPORT
7 2 ÎÒµÄÊÂÇé NOTIFY
8 4 Ìá°¸ RESOLUTION
9 4 ½¨Òé SUGGESTION
e.g.: table: temp_t2£º
results:
1 1 ÊÕÎÄ SHOUWEN
2 1 ·¢ÎÄ FAWEN
3 1 ½»°ì JIAOBAN
4 2 Öµ°à±¨¸æ REPORT
5 3 ¶½²ì¶½°ì  
Ïà¹ØÎĵµ£º
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´´½¨´¥·¢Æ÷µÄÓï·¨È ......
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CREATE OR REPLACE TYPE Obj1 AS OBJECT (
f1 NUMBER,
f2 VARCHAR2(10),
f3 DATE
);
/
CREATE OR REPLACE TYPE Obj2 AS OBJECT (
f1 DATE,
f2 CHAR(1)
);
/
CREATE OR REPLACE TYPE Obj3 AS OBJECT (
a Obj1,
b Obj2
);
/
OBJ3ÒÀÀµÓÚOBJ ......
oracle ·½·¨ & ......
Differring Constraints:
Constraints can have the following attributes: DEFFERRABLE / NOT DEFFERRABLE, INITIALLY DEFFERRED / INITIALLY IMMEDIATE.
e.g.:
alter table dept2 add constraint dept2_id_pk primary key (department_id) deferrable initially deferred; // deferring constraint on creation. ......