The trigger is updating multiple rows with the same value
Here a problem, I'm trying to update one or many rows in a table(B), but its updating the rows with the same value let's say
TABLE A
+------+-----+-----+
|ROWID |NAME |CODE |
+------+-----+-----+
| 123 |pepe | 1 |
| 456 |tito | 2 |
| 789 |gege | 3 |
-------------------
Current result:
+------+-----+-----+---------+
|ROWID |NAME |CODE | A_ROWID |
+------+-----+-----+---------+
| 321 |rolo | 1 | 123 |
| 654 |kit | 2 | 123 |
| 987 |gu | 3 | 123 |
-----------------------------
Expected result:
+------+-----+-----+---------+
|ROWID |NAME |CODE | A_ROWID |
+------+-----+-----+---------+
| 321 |rolo | 1 | 123 |
| 654 |kit | 2 | 456 |
| 987 |gu | 3 | 789 |
-----------------------------
This is the trigger, I will really appreciate any advice
ALTER TRIGGER [dbo].[TRIG_AfterInsert]
ON [dbo].[B]
AFTER INSERT
AS
BEGIN
DECLARE #Code nvarchar(100);
SELECT #Code = CODE FROM INSERTED;
UPDATE B
SET B.A_ROWID = A.ROWID
FROM A
WHERE A.CODE = #Code;
END
The trigger is called once per the statement, which means if you are updating one row it will be called once, if you are updating 1 million rows it will be called once again.
So, now when you know triggers core behavior you should refactor these lines below:
declare #Code nvarchar(100);
select #Code=CODE from INSERTED;
So, full trigger code will be:
CREATE OR ALTER TRIGGER dbo.TRIG_AfterInsert ON dbo.B AFTER INSERT AS
BEGIN
UPDATE B
SET B.A_ROWID = A.ROWID
FROM B
JOIN INSERTED I ON I.ROWID = B.ROWID
JOIN A ON A.CODE = I.CODE;
END
Just take a look there is inserted table directly in the join, and with this statement you will filter all the rows you need.
Where clause in your statement is converted in the JOIN.
Related
I have a table "table1" like this:
+------+--------------------+
| id | barcode | lot |
+------+-------------+------+
| 0 | ABC-123-456 | |
| 1 | ABC-123-654 | |
| 2 | ABC-789-EFG | |
| 3 | ABC-456-EFG | |
+------+-------------+------+
I have to extract the number in the center of the column "barcode", like with this request :
SELECT SUBSTR(barcode, 5, 3) AS ToExtract FROM table1;
The result:
+-----------+
| ToExtract |
+-----------+
| 123 |
| 123 |
| 789 |
| 456 |
+-----------+
And insert this into the column "lot" .
follow along the lines
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
i.e in your case
UPDATE table_name
SET lot = SUBSTR(barcode, 5, 3)
WHERE condition;(if any)
UPDATE table1 SET Lot = SUBSTR(barcode, 5, 3)
-- WHERE ...;
Many databases support generated (aka "virtual"/"computed" columns). This allows you to define a column as an expression. The syntax is something like this:
alter table table1 add column lot varchar(3) generated always as (SUBSTR(barcode, 5, 3))
Using a generated column has several advantages:
It is always up-to-date.
It generally does not occupy any space.
There is no overhead when creating the table (although there is overhead when querying the table).
I should note that the syntax varies a bit among databases. Some don't require the type specification. Some use just as instead of generated always as.
CREATE TABLE Table1(id INT,barcode varchar(255),lot varchar(255))
INSERT INTO Table1 VALUES (0,'ABC-123-456',NULL),(1,'ABC-123-654',NULL),(2,'ABC-789-EFG',NULL)
,(3,'ABC-456-EFG',NULL)
UPDATE a
SET a.lot = SUBSTRING(b.barcode, 5, 3)
FROM Table1 a
INNER JOIN Table1 b ON a.id=b.id
WHERE a.lot IS NULL
id | barcode | lot
-: | :---------- | :--
0 | ABC-123-456 | 123
1 | ABC-123-654 | 123
2 | ABC-789-EFG | 789
3 | ABC-456-EFG | 456
db<>fiddle here
SQL SERVER 2014
I need to update two columns in TargetTable with values from SourceTable
SourceTbl
PersonNr | Block | BlockReason |
---------|----------|---------------|
000001 | 1 | abuse |
000001 | 1 | age |
000001 | 0 | memo |
000002 | 1 | age |
000002 | 0 | |
000003 | 0 | |
000003 | 0 | |
000004 | 1 | behaviour |
000005 | 0 | |
TargetTable
PersonNr | Block | BlockReason |
---------|----------|---------------|
000001 | 0 | |
000001 | 0 | |
000002 | 0 | |
000002 | 0 | |
000004 | 1 | |
000005 | 0 | |
Result needed:
PersonNr | Block | BlockReason |
---------|----------|---------------|
000001 | 1 | abuse |
000001 | 1 | abuse |
000002 | 1 | age |
000002 | 1 | age |
000004 | 1 | behaviour |
000005 | 0 | |
It is not relevant which BlockReason Person 1 gets,
as far as it's one from a row where Block = '1'.
I've tried this pretty straight-forward update :
UPDATE
src
SET
src.Block = '1',
src.BlockReason = targ.BlockReason
FROM
SourceTbl src
INNER JOIN
TargetTable targ
ON
src.PersonNr= targ.PersonNr
WHERE src.Block = '1'
But ended up with faulty result-rows where Block and Reason are updated separately :
PersonNr | Block | BlockReason |
---------|----------|---------------|
000001 | 1 | memo |
Next I've tried :
MERGE INTO TargetTable AS TGT
USING
(
SELECT Block, BlockReason, PersonNr
FROM SourceTbl
GROUP BY Block, BlockReason, PersonNr
) AS SRC
ON
SRC.PersonNr= TGT.PersonNr AND
SRC.Block= '1'
WHEN MATCHED THEN
UPDATE SET TGT.Block= SRC.Block, TGT.BlockReason= SRC.BlockReason;
Got the error
The MERGE statement attempted to UPDATE or DELETE the same row more than once. This happens when a target row matches more than one source row. A MERGE statement cannot UPDATE/DELETE the same row of the target table multiple times. Refine the ON clause to ensure a target row matches at most one source row, or use the GROUP BY clause to group the source rows.
Any help? Hugely appreciated! Truly. Totally.
The problem with your query is that it gives duplicate values and it's trying to update the same record more than once.And the GROUP BY in the subquery doesn't make any sense since you are not using any aggregate function.
Let's take an id(say 1) and check what's going wrong with your query.
src.PersonNr | src.Block | src.BlockReason | tgt.PersonNr | tgt.Block | tgt.BlockReason |
-------------|--------------|-------------------|--------------
000001 | 1 | abuse | 000001 | 0 | |
000001 | 1 | age | 000001 | 0 | |
000001 | 1 | abuse | 000001 | 0 | |
000001 | 1 | age | 000001 | 0 | |
Your query will give you the above result and try to update targettable 2 times for each record once with abuse and next with age.
You can try the below query:
MERGE INTO TargetTable AS TGT
USING
(
SELECT Block, BlockReason, PersonNr
FROM(
SELECT Block, BlockReason, PersonNr,ROW_NUMBER() OVER (PARTITION BY PersonNr ORDER BY [YourPrimaryKey]) RN
FROM SourceTbl ) X
WHERE X.RN=1
) AS SRC
ON
SRC.PersonNr= TGT.PersonNr AND
SRC.Block= '1'
WHEN MATCHED THEN
UPDATE SET TGT.Block= SRC.Block, TGT.BlockReason= SRC.BlockReason;
You have duplicates in your data. Add another (or more than one) column to the ON clause of the MERGE that will help identify exactly one record or find a way to remove duplicates before merging.
The UPDATE should be something like this:
UPDATE
targ
SET
Block = '1',
BlockReason = src.BlockReason
FROM
SourceTbl src
INNER JOIN
TargetTable targ
ON
src.PersonNr= targ.PersonNr
WHERE src.Block = '1'
Since we're only using rows from SourceTbl where Block is 1, it should not be possible for a row affected by this update to end up with a reason which had a Block of 0.
There is still the general issue that this is non-deterministic in cases where multiple rows from SourceTbl are joined to one row in TargetTbl, but since you've indicated that determinism isn't required here, it shouldn't result in a problem.
Given data structure:
I have the following table My_List, where Sup_ID is Primary Key
My_List
+--------+----------+-----------+
| Sup_ID | Sup_Name | Sup_Code |
+--------+----------+-----------+
| 1 | AA | 23 |
| 2 | BB | 87 |
| 3 | CC | 90 |
+--------+----------+-----------+
And the following table _MyList_details, where Buy_ID is Primary Key and Sup_ID is Foreign Key points at My_List.Sup_ID
My_List_details
+--------+--------+------------+------------+------------+
| Buy_ID | Sup_ID | Sup_Detail | Max_Amount | Min_Amount |
+--------+--------+------------+------------+------------+
| 23 | 1 | AAA | 1 | 10 |
| 33 | 2 | BBB | 11 | 20 |
| 43 | 3 | CCC | 21 | 30 |
+--------+--------+------------+------------+------------+
Finally, I have the table My_Sequence as follow:
My_Sequence
+-----+------+
| Seq | Name |
+-----+------+
| 4 | x |
| 5 | y |
| 6 | z |
+-----+------+
---------------------------------------------------
Objectives
Write PL/SQL script to:
Using a cursor, I need to copy My_List records and re-insert it with the new Sup_ID copied from My_Sequence.Seq.
I need to copy My_List_details records and re-insert them with the new Sup_ID foreign key.
------------------------------------------------------------------------------
Expected Outcome
My_List
+--------+----------+----------+
| Sup_ID | Sub_Name | Sub_Code |
+--------+----------+----------+
| 1 | AA | 23 |
| 2 | BB | 87 |
| 3 | CC | 90 |
| 4 | AA | 23 |
| 5 | BB | 87 |
| 6 | CC | 90 |
+--------+----------+----------+
My_List_details
+--------+--------+------------+------------+------------+
| Buy_ID | Sup_ID | Sub_Detail | Max_Amount | Min_Amount |
+--------+--------+------------+------------+------------+
| 23 | 1 | AAA | 1 | 10 |
| 33 | 2 | BBB | 11 | 20 |
| 43 | 3 | CCC | 21 | 30 |
| 53 | 4 | AAA | 1 | 10 |
| 63 | 5 | BBB | 11 | 20 |
| 73 | 6 | CCC | 21 | 30 |
+--------+--------+------------+------------+------------+
What I have started with is the following:
DECLARE
NEW_Sup_ID Sup_ID%type := Seq;
c_Sup_Name Sup_Name%type;
c_Sup_Code Sup_Code%type;
c_Buy_ID Buy_ID%type;
c_Sup_Detail Sup_Detail%type;
c_Max_Amount Max_Amount%type
c_My_Min_Amount Min_Amount%type
CURSOR c_My_List
IS
SELECT * FROM My_List;
CURSOR c_My_List_details
IS
SELECT * FROM My_List_details
BEGIN
FETCH c_My_List INTO NEW_Sup_ID, c_Sup_Name, c_Sup_Code;
INSERT INTO My_List;
FETCH c_My_List_details INTO c_Buy_ID, NEW_Sup_ID, c_Sup_Detail, c_Max_Amount, c_Min_Amount
INSERT INTO My_List_details
END;
/
Aside from the syntax errors, I do not see my script copy row by row and insert them to both tables accordingly. Further, the number of My_Sequence records is bigger than the number of My_List records. So what I need is, if My_List records are 50, I need the script to copy the first 50 Seq from My_Sequence.
---------------------------------------------------------------------------------
Question
How to achieve this result? I have searched and found Tom Kyte for cascade update but I am not sure if I do need to use this package, I am a bit beginner in PL/SQL and it is a bit complicated for me to utilize such a comprehensive package. Further, it's for cascade update and my case is about re-insert. I'd appreciate any help
The following Sql Statements will perform the task on the schema defined at this SqlFiddle. Note that I have changed a couple of field and table names - because they clash with Oracle terms. SqlFiddle seems to have some problems with my code, but it has been tested on another (amphibious) client which shall remain nameless.
The crucial point (As I said in my comments) is deriving a rule to map old sequence number to new. The view SEQUENCE_MAP performs this task in the queries below.
You may be disappointed by my reply because it depends upon there being the exact same number of sequence records as LIST/LIST_DETAILS, and hence it can only be run once. Your final PL/SQL can perform the necessary checks, I hope.
Hopefully it is a matter of refining the sequence_map logic to get you where you want to be.
Avoid using cursors; ideally when manipulating relational data you need to think in terms of sets of data rather than rows. This is because if you use set-thinking Oracle can do its magic in optimising, parallelising and so-on. Oracle is brilliant at scaling up - If a table is split over multiple disks, for example, it may process your request with data from the multiple disks simultaneously. If you force it into a row-by-row, procedural logic you may find that the applications you write do not scale up well.
CREATE OR REPLACE VIEW SEQUENCE_MAP AS (
SELECT OLD_SEQ, NEW_SEQ FROM
(
( SELECT ROWNUM AS RN, SUP_ID AS OLD_SEQ FROM
(SELECT SUP_ID FROM LIST ORDER BY SUP_ID) ) O
JOIN
( SELECT ROWNUM AS RN, SUP_ID AS NEW_SEQ FROM
(SELECT SEQ AS SUP_ID FROM SEQUENCE_TABLE ORDER BY SEQ) ) N
ON N.RN = O.RN
)
);
INSERT INTO LIST
(
SELECT
NEW_SEQ, SUB_NAME, SUB_CODE
FROM
SEQUENCE_MAP
JOIN LIST L ON
L.SUP_ID = SEQUENCE_MAP.OLD_SEQ
);
INSERT INTO LIST_DETAILS
(
SELECT
BUY_ID, NEW_SEQ, SUB_DETAIL, MAX_FIELD, MIN_FIELD
FROM
SEQUENCE_MAP
JOIN LIST_DETAILS L ON
L.SUP_ID = SEQUENCE_MAP.OLD_SEQ
);
I would do 2 inner loops, and search the next sequence to use.
I imagine the new buy_id is assigned via trigger using a sequence, or something equivalent, else you'll have to generate it in your code.
I have no Oracle database available to test it, so don't pay attention to syntax.
DECLARE
NEW_Sup_ID Sup_ID%type := Seq;
c_Sup_ID Sup_ID%type := Seq;
c_Sup_Name Sup_Name%type;
c_Sup_Code Sup_Code%type;
c_Buy_ID Buy_ID%type;
c_Sup_Detail Sup_Detail%type;
c_Max_Amount Max_Amount%type;
c_My_Min_Amount Min_Amount%type;
CURSOR c_My_List
IS
SELECT * FROM My_List;
CURSOR c_My_List_details
IS
SELECT * FROM My_List_details where sup_id=c_Sup_ID;
BEGIN
for c_My_List IN c_Sup_ID, c_Sup_Name, c_Sup_Code loop
select min(seq) from My_sequence into NEW_Sup_ID;
INSERT INTO My_List (sup_id,...) values (NEW_Sup_ID,...);
for c_My_List_details IN c_Buy_ID, NEW_Sup_ID, c_Sup_Detail, c_Max_Amount, c_Min_Amount loop
INSERT INTO My_List_details (sup_id, ...) values (NEW_Sup_ID,...);
end loop;
deelte from from My_sequence where seq= NEW_Sup_ID;
end loop;
commit;
END;
/
I have a table name table containing two columns foreign_table_name, and foreign_key.
Is it possible to write a SELECT query that would JOIN values of this table and the table which name is specified in the column foreign_table_name ?
For instance, if we know that all possible targetted foreign tables have a name field, I would like to know if I could write something that would:
SELECT table.foo, table.bar, foreign_table.name
FROM table
JOIN $foreign_table AS foreign_table
ON (foreign_table.id = table.foreign_key
$foreign_table = table.foreign_table);
Any solution using PlpgSQL is of course accepted.
Here's a simple content:
Table ``table``
------------------------------------------------
| foo | bar | foreign_table_name | foreign_key |
------------------------------------------------
| A | 1 | fruits | 8 |
| B | 2 | vegetable | 5 |
------------------------------------------------
Table ``fruit``
---------------
| id | name |
---------------
| 8 | apple |
---------------
Table ``vegetable``
----------------
| id | name |
----------------
| 5 | carrot |
----------------
The expected result table would be:
----------------------
| foo | bar | name |
----------------------
| A | 1 | apple |
| B | 2 | carrot |
----------------------
EDIT: I added the full table example in an attempt to be clearer.
It's usually way easier to do this sort of thing on the client side, but if you want it's possible with PL/PgSQL, e.g.
CREATE OR REPLACE FUNCTION dynamic_call(tblname text)
RETURNS TABLE (foo int, bar text, fname text)
AS $$
BEGIN
RETURN QUERY EXECUTE format('
SELECT t.foo, table.bar, f."name"
FROM mytable t
JOIN %I AS f ON (f.id = t.foreign_key);', tblname);
END;
$$ LANGUAGE plpgsql;
For more information, see the PL/PgSQL documentation.
Given a table like below, is there a single-query way to update the table from this:
| id | type_id | created_at | sequence |
|----|---------|------------|----------|
| 1 | 1 | 2010-04-26 | NULL |
| 2 | 1 | 2010-04-27 | NULL |
| 3 | 2 | 2010-04-28 | NULL |
| 4 | 3 | 2010-04-28 | NULL |
To this (note that created_at is used for ordering, and sequence is "grouped" by type_id):
| id | type_id | created_at | sequence |
|----|---------|------------|----------|
| 1 | 1 | 2010-04-26 | 1 |
| 2 | 1 | 2010-04-27 | 2 |
| 3 | 2 | 2010-04-28 | 1 |
| 4 | 3 | 2010-04-28 | 1 |
I've seen some code before that used an # variable like the following, that I thought might work:
SET #seq = 0;
UPDATE `log` SET `sequence` = #seq := #seq + 1
ORDER BY `created_at`;
But that obviously doesn't reset the sequence to 1 for each type_id.
If there's no single-query way to do this, what's the most efficient way?
Data in this table may be deleted, so I'm planning to run a stored procedure after the user is done editing to re-sequence the table.
You can use another variable storing the previous type_id (#type_id). The query is ordered by type_id, so whenever there is a change in type_id, sequence has to be reset to 1 again.
Set #seq = 0;
Set #type_id = -1;
Update `log`
Set `sequence` = If(#type_id=(#type_id:=`type_id`), (#seq:=#seq+1), (#seq:=1))
Order By `type_id`, `created_at`;
I don't know MySQL very well, but you could use a sub query though it may be very slow.
UPDATE 'log' set 'sequence' = (
select count(*) from 'log' as log2
where log2.type_id = log.type_id and
log2.created_at < log.created_at) + 1
You'll get duplicate sequences, though, if two type_ids have the same created_at date.