I have create a table person(id, name ,samenamecount).The samenamecount attribute can be null but for each row can store the row count for same names.I am achieving this by calling a stored procedure inside a after insert trigger.Below is my code.
create or replace procedure automatic(s in person.name%type)
AS
BEGIN
update person set samenamecount=(select count(*) from person where name=s) where name=s;
END;
create or replace trigger inserttrigger
after insert
on person
for each row
declare
begin
automatic(:new.name);
end;
On inserting a row it is giving error like
table ABCD.PERSON is mutating, trigger/function may not see it.
Can somebody help me to figure out this?
If you have the table:
CREATE TABLE person (
id NUMBER
GENERATED ALWAYS AS IDENTITY
CONSTRAINT person__id__pk PRIMARY KEY,
name VARCHAR2(20)
NOT NULL
);
Then rather than creating a trigger, instead, you could use a view:
CREATE VIEW person_view (
id,
name,
samenamecount
) AS
SELECT id,
name,
COUNT(*) OVER (PARTITION BY name)
FROM person;
You can use the trigger:
CREATE TRIGGER inserttrigger
AFTER INSERT ON person
BEGIN
MERGE INTO person dst
USING (
SELECT ROWID AS rid,
COUNT(*) OVER (PARTITION BY name) AS cnt
FROM person
) src
ON (src.rid = dst.ROWID)
WHEN MATCHED THEN
UPDATE SET samenamecount = src.cnt;
END;
/
fiddle
If you want to make it more efficient then you could use a compound trigger and collate the names that are being inserted and only update the matching rows.
Related
I have a table with multiple columns and one (unique key) should be a value composed from the values of other two columns.
CREATE TABLE batches (
id TEXT PRIMARY KEY UNIQUE,
name TEXT NOT NULL,
project_id INTEGER);
On each insert, I want to generate the id based on the value of 'name' and 'project_id' (this one can be null):
INSERT INTO batches (name,project_id) VALUES
('21.01',NULL),
('21.01',1),
('21.02',2);
So, I have created a table TRIGGER but doesn't execute.
CREATE TRIGGER create_batches_id
AFTER INSERT ON batches FOR EACH ROW
BEGIN
UPDATE batches
SET id = SELECT quote(name ||"_"|| (CASE project_id
WHEN NULL THEN '' ELSE project_id END )
FROM batches WHERE rowid = (SELECT MAX(rowid) FROM batches))
WHERE rowid = (SELECT MAX(rowid) FROM batches);
END;
Error:
SQL Error [1]: [SQLITE_ERROR] SQL error or missing database (near "SELECT": syntax error)
I expect:
id = 21.01_
id = 21.01_1
id = 21.01_2
What am I doing wrong? If I run only the SELECT/CASE statment it returns ok: '21.01_2'
I have also tried without the quote() function, no success.
UPDATE I:
I have managed to execute the whole create trigger statement (parenthesis were missing):
CREATE TRIGGER create_batch_id
AFTER INSERT ON batches FOR EACH ROW
BEGIN
UPDATE batches
SET id = (SELECT name ||"_"|| (CASE project_id WHEN NULL THEN 0 ELSE project_id END ) FROM batches WHERE rowid = (SELECT MAX(rowid) FROM batches) )
WHERE rowid = (SELECT MAX(rowid) FROM batches);
END;
It seems my editor (DBeaver) has a glitch with the following new line character. If it is inside the selection it runs into this exception (or I am missing something):
SQL Error [1]: [SQLITE_ERROR] SQL error or missing database (incomplete input)
If I manually select only the above lines (from CREATE to ;), the trigger is created, however, not the expected result. If value in project_id is NULL, no id value is created.
Don't add the column id in the table.
Instead define the combination of name and project_id as the PRIMARY KEY of the table, so that it is also UNIQUE:
CREATE TABLE batches (
name TEXT NOT NULL,
project_id INTEGER,
PRIMARY KEY(name, project_id)
)
Then, whenever you need that id you can run a query:
SELECT name || '_' || COALESCE(project_id, '') AS id,
name,
project_id
FROM batches
Or create a view:
CREATE VIEW v_batches AS
SELECT name || '_' || COALESCE(project_id, '') AS id,
name,
project_id
FROM batches
and query the view:
SELECT * FROM v_batches
See the demo.
Or if your version of SQLite is 3.31.0+ you can have the column id as a generated column:
CREATE TABLE batches (
name TEXT NOT NULL,
project_id INTEGER,
id TEXT GENERATED ALWAYS AS (name || '_' || COALESCE(project_id, '')),
PRIMARY KEY(name, project_id)
);
i have a table with 4 columns
1.msisdn
2.accountnumber
3.cardnumber
4.subscriptiondate
I want to add a trigger to this table. If the data i am inserting is
1.99999999
2.2
3.3298572857239
4.(this can be blank)
and the data that is currently in the table is
1.99999999
2.1
3.3298572857239
4.(this can be blank)
Trigger should check if there is this msisdn 99999999 is already having a record with this cardnumber 3298572857239. If there is a record already existing in the table, the trigger should delete the existing entry and insert the new one. The final result should look like this
1.99999999
2.1
3.3298572857239
4.(this can be blank)
I want to keep the value of accountnumber same before and after the trigger. This is what i have tried so far but for this trigger, i am not getting any data in accountnumber column. Please someone help
DROP TRIGGER TRIG_TABLEA;
CREATE OR REPLACE TRIGGER TRIG_TABLEA
BEFORE INSERT ON TABLEA
REFERENCING OLD AS Old NEW AS New
FOR EACH ROW
BEGIN
:new.accountnumber := :old.accountnumber;
DELETE FROM TABLEA WHERE MSISDN = :new.MSISDN AND CARDNUMBER = :new.CARDNUMBER;
:new.MSISDN := :new.MSISDN;
:new.CARDNUMBER := :new.CARDNUMBER;
:new.accountnumber := :old.accountnumber;
END;
/
Don't do a delete-and-insert. You want MERGE. The only thing that can change in your statement is accountnumber and subscriptiondate. You don't say where the data is coming from, so I assume this is a PL/SQL procedure with p_* as the parameters. So you want something like this:
MERGE INTO mytable trg
USING ( SELECT p_accountnumber, p_subscriptiondate FROM dual ) src
ON ( trg.msisdn = p_msisdn AND trg.cardnumber )
WHEN NOT MATCHED INSERT ( msisdn, accountnumber, cardnumber, subscriptiondate )
VALUES ( p_msisdn, p_accountnumber, p_cardnumber, p_subscriptiondate )
WHEN MATCHED SET ( cardnumber = p_cardnumber, subscriptiondate = p_subscriptiondate)
This will do an insert if the row doesn't exist or update an existing row if it does.
I am passing datatable as input parameter to stored procedure. Datatable contains id, Name,Lname,Mobileno,EmpId.
Employee table contains [Name],[Lname],[mobno],[Did] as columns.
When user is logged in, his Id come as DId. There are more than 1000 records. Instead of passing that id to datatable, I have created
separete parameter to sp. I want to add records to Employee table, which are not already exist. If combination of mobileno and Did already exists, then
don't insert into Employee table, else insert. Datatable may contain records, which can be duplicate. So I don't want to include that record. I want select only
distinct records and add them to table. I am intrested in mobile no. If there are 10 record having same moble no, I am fetching record, which comes first.
Following code is right or wrong. According to my knowledge, first from clause, then inner join, then where, then select execute. Record get fetched from datatable,
then inner join happens generate result, from that result not from datatable it will check record. So it will give me proper output.
Create Procedure Proc_InsertEmpDetails
#tblEmp EmpType READONLY,
#DId int
as
begin
INSERT INTO Employee
([Name],[Lname],[mobno],[Did])
SELECT [Name],[Lname],[mobno] #DId
FROM #tblEmp A
Inner join (
select min(Id) as minID, mobno from #tblEmp group by mobno
) MinIDTbl
on MinIDTbl.minID = A.ExcelId
WHERE NOT EXISTS (SELECT 1
FROM Employee B
WHERE B.[mobno] = A.[mobno]
AND B.[Did] = #DId )
end
or does I need to change like this
INSERT INTO Employee
([Name],[Lname],[mobno],[Did])
SELECT C.[Name],C.[Lname],C.[mobno], C.D_Id
from
(SELECT [Name],[Lname],[mobno] #DId as D_Id
FROM #tblEmp A
Inner join (
select min(Id) as minID, mobno from #tblEmp group by mobno
) MinIDTbl
on MinIDTbl.minID = A.ExcelId
)C
WHERE NOT EXISTS (SELECT 1
FROM Employee B
WHERE B.[mobno] = C.[mobno]
AND B.[Did] = #DId )
I'm planning to do SQL expert examination.
I have doubts that answer D is correct:
Evaluate the following command:
CREATE TABLE employees
( employee_id NUMBER(2) PRIMARY KEY
, last_name VARCHAR2(25) NOT NULL
, department_id NUMBER(2)NOT NULL
, job_id VARCHAR2(8)
, salary NUMBER(10,2));
You issue
the following command to create a view that displays the IDs and last
names of the sales staff in the organization:
CREATE OR REPLACE VIEW sales_staff_vu AS
SELECT employee_id, last_name,job_id
FROM employees
WHERE job_id LIKE 'SA_%'
WITH CHECK OPTION;
Which two statements are true regarding the above view? (Choose two.)
A. It allows you to insert rows into the EMPLOYEES table .
B. It allows you to delete details of the existing sales staff from
the EMPLOYEES table.
C. It allows you to update job IDs of the existing sales staff to any
other job ID in the EMPLOYEES table.
D. It allows you to insert IDs, last names, and job IDs of the sales
staff from the view if it is used in multitable INSERT statements.
Source
A is FALSE as the view doesn't allow inserting into the department_id column which is mandatory.
B is TRUE, although it would be more accurate to say that the view only allows deletions of employees where the job_id matches the predicate LIKE 'SA_%'.
C is FALSE, as the WITH CHECK OPTION means that you can't change the job_id if the new job_id doesn't match the view's predicate.
D is FALSE: a multitable insert statement can't just insert some columns into the view and the remaining columns into the employees table. Even if you join the view to the table, the insert must still insert into the base table, not into the view:
insert into
(select e.employee_id, e.last_name, e.department_id, e.job_id
from sales_staff_vu v
join employees e
on v.employee_id = e.employee_id)
values
(1, 'KEMP', 2, 'SA_X');
I suspect this is a test of your ability to verify and ignore wrong information on the internet - i.e. 99% of sites say D is true!
Now, my answer can be easily disproved by crafting a multitable insert statement that successfully inserts via the view.
According to my knowledge answer D is wrong.Reasons are
1.If A is wrong, definitely D is wrong.because department_id column is mandatory field on the table, but it is not mentioned in view.so we can't insert a row using this view.
2.In Answer D,multitable INSERT statements are INSERT ALL, INSERT FIRST,etc.
to check this Answer,i have tried these steps
CREATE TABLE employees123
( employee_id NUMBER(2) PRIMARY KEY
, last_name VARCHAR2(25) NOT NULL
, department_id NUMBER(2)NOT NULL
, job_id VARCHAR2(8)
, salary NUMBER(10,2));
CREATE OR REPLACE VIEW sales_staff_vu123 AS
SELECT employee_id, last_name,job_id,department_id
FROM employees123
WHERE job_id LIKE 'SA_%'
WITH CHECK OPTION;
--department_id is added to view
--here i am trying to insert my employees table rows to employees123 table
INSERT ALL
INTO sales_staff_vu123 --using View
SELECT employee_id, last_name,job_id,department_id
FROM employees;
Error at Command Line:153 Column:15
Error report:
SQL Error: ORA-01702: a view is not appropriate here
01702. 00000 - "a view is not appropriate here"
*Cause:
*Action:
So my decision is we cant use views with multitable insert statements.
I want to create a table with a field that is unique and limited to a certain value. Lets say that the limit is 100, the table is full, I remove a random row, and when I create a new row it has the value that was freed before.
It doesn't need to be the fastest thing in the world (the limit is quite small), I just want to implement it in a DB.
Any ideas?
Create one more column in main table, say deleted (integer, 0 or 1). When you need to delete with certain id, do not really delete it, but simply update deleted to 1:
UPDATE mytable SET deleted=1 WHERE id = <id_to_delete>
When you need to insert, find id to be reused:
SELECT id FROM mytable WHERE deleted LIMIT 1
If this query returns empty result, then use INSERT to create new id. Otherwise, simply update your row:
UPDATE mytable SET deleted=0, name='blah', ... WHERE id=<id_to_reuse>
All queries reading from your main table should have WHERE constraint with NOT deleted condition:
SELECT * FROM mytable WHERE NOT deleted
If you add index on deleted, this method should work fast even for large number of rows.
This solution does everything in a trigger, so you can just use a normal INSERT.
For the table itself, we use an autoincrementing ID column:
CREATE TABLE MyTable(ID INTEGER PRIMARY KEY, Name);
We need another table to store an ID temporarily:
CREATE TABLE moriturus(ID INTEGER PRIMARY KEY);
And the trigger:
CREATE TRIGGER MyTable_DeleteAndReorder
AFTER INSERT ON MyTable
FOR EACH ROW
WHEN (SELECT COUNT(*) FROM MyTable) > 100
BEGIN
-- first, select a random record to be deleted, and save its ID
DELETE FROM moriturus;
INSERT INTO moriturus
SELECT ID FROM MyTable
WHERE ID <> NEW.ID
ORDER BY random()
LIMIT 1;
-- then actually delete it
DELETE FROM MyTable
WHERE ID = (SELECT ID
FROM moriturus);
-- then change the just inserted record to have that ID
UPDATE MyTable
SET ID = (SELECT ID
FROM moriturus)
WHERE ID = NEW.ID;
END;