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2025-01-16 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Database >
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This article is about how to manipulate the big data collection in the database. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.
1. Insert data by subquery
1. Grammar
INSERT INTO table [column (, column)] subquery
2. Description:
You can use the insert statement to add rows to a table with values from the query result set.
The number of columns and their data types in the column list that inserts the clause must match the values and data types in the subquery.
3. Example sentence:
INSERT INTO EMPL3
SELECT *
FROM employees
II. WITH CHECK OPTION
1. Grammar:
Insert into (WITH CHECK OPTION) values (...)
2. Description:
Insert goes into this table in subquery.
Insertion is not allowed if the where condition in subquery is not met.
If the inserted column is not in the where condition checked by subquery, then the insert will not be allowed.
If you do not add WITH CHECK OPTION, it will not be checked at insert time.
Note here that subquery is not actually implemented.
3. Example sentences
INSERT INTO
(SELECT EMPLOYEE_ID, LAST_NAME, EMAIL, HIRE_DATE, JOB_ID, SALARY
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 50 WITH CHECK OPTION)
VALUES
(99998
'Smith'
'JSMITH'
TO_DATE ('1999-06-07,' yyyy-mm-dd')
'ST_CLERK'
5000)
III. INSERT ALL
1. Grammar:
A) unconditional
INSERT [ALL] [conditional_insert_clause]
[insert_into_clause values_clause] (subquery)
B) conditional
INSERT [ALL]
[WHEN condition THEN] [insert_into_clause values_clause]
[ELSE] [insert_into_clause values_clause]
2. Description
A) if there is no when condition, all tables will be inserted
B) if there is a when condition, each when condition is checked and the insert operation is performed if the condition is met.
3. Example sentence:
-- unconditional
INSERT ALL
INTO SAL_HISTORY
VALUES (EMPID, HIREDATE, SAL)
INTO MGR_HISTORY
VALUES (EMPID, MGR, SAL)
SELECT EMPLOYEE_ID EMPID, HIRE_DATE HIREDATE, SALARY SAL, MANAGER_ID MGR
FROM EMPLOYEES
WHERE EMPLOYEE_ID > 200
-- conditional
INSERT ALL
WHEN SAL > 10000
THEN INTO SAL_HISTORY
VALUES (EMPID, HIREDATE, SAL)
WHEN MGR > 200
THEN INTO MGR_HISTORY
VALUES (EMPID, MGR, SAL)
SELECT EMPLOYEE_ID EMPID, HIRE_DATE HIREDATE, SALARY SAL, MANAGER_ID MGR
FROM EMPLOYEES
WHERE EMPLOYEE_ID > 200
IV. INSERT FIRST
1. Grammar:
INSERT [FIRST]
[WHEN condition THEN] [insert_into_clause values_clause]
[ELSE] [insert_into_clause values_clause]
2. Description:
For each row of data, only the table where the first when condition holds is inserted, and no other conditions are checked.
3. Example sentence:
INSERT FIRST
WHEN SAL > 25000
THEN INTO SPECIAL_SAL
VALUES (DEPTID, SAL)
WHEN HIREDATE LIKE ('%')
THEN INTO HIREDATE_HISTORY_00
VALUES (DEPTID, HIREDATE)
WHEN HIREDATE LIKE ('% 99%')
THEN INTO HIREDATE_HISTORY_99
VALUES (DEPTID, HIREDATE)
ELSE INTO HIREDATE_HISTORY
VALUES (DEPTID, HIREDATE)
SELECT DEPARTMENT_ID DEPTID, SUM (SALARY) SAL, MAX (HIRE_DATE) HIREDATE
FROM EMPLOYEES
GROUP BY DEPARTMENT_ID
5. MERGE
1. Grammar:
MERGE INTO table_name table_alias
USING (table | view | sub_query) alias
ON (join condition)
WHEN MATCHED THEN
UPDATE SET
Col1 = col_val1
Col2 = col2_val
WHEN NOT MATCHED THEN
INSERT (column_list)
VALUES (column_values)
2. Description:
Merge is used to select data updates from one table or insert them into another table. In the end, whether to update or insert depends on the conditions in the statement.
3. Example sentence:
MERGE INTO empl3 c
USING employees e
ON (c.employee_id = e.employee_id)
WHEN MATCHED
THEN UPDATE SET
C.first_name = e.first_name
C.last_name = e.last_name
...
C.department_id = e.department_id
WHEN NOT MATCHED
THEN INSERT VALUES
(e.employee_id, e.first_name, e.last_name
E.email, e.phone_number, e.hire_date, e.job_id
E.salary, e.commission_pct, e.manager_id
E.department_id)
VI. Flashback Version Query
1. Grammar:
VERSIONS BETWEEN TIMESTAMP [lower bound] AND [upper bound]
VERSIONS BETWEEN SCN [lower bound] AND [upper bound]
2. Description:
Through versions between, you can view different versions of records in the undo table space within a specified period of time.
3. Example sentence:
SELECT SALARY
FROM EMPLOYEES3 VERSIONS BETWEEN SCN MINVALUE AND MAXVALUE
WHERE EMPLOYEE_ID = 107
Thank you for reading! This is the end of the article on "how to operate a large dataset in the database". I hope the above content can be of some help to you, so that you can learn more knowledge. If you think the article is good, you can share it for more people to see!
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