I need to insert some rows to tables in PostgreSQL. But before inserting the row into table, I should check whether the record is existing or not by using update statement. If update statement returns 0 rows, then I can insert, otherwise I can skip that insertion. I should write SQL statements for this in .sql file in PostgreSQL.
How to achieve this?
In Oracle we have below format:
declare
i number;
begin
update employees set status = 'fired' where name like '%Bloggs';
i := sql%rowcount;
IF i ==0 THEN
insert statement here
end
How can I achieve this in Postgres?
If concurrency is not a problem for you, and you want to do it in a plpgsql function, rather use the special variable FOUND:
DO
$do$
BEGIN
UPDATE employees SET status = 'fired' WHERE ... ;
IF NOT FOUND THEN
-- insert statement here
END IF;
END
$do$
Or use a data-modifying CTE:
Insert if not exists else update it in Netezza
Optimize INSERT / UPDATE / DELETE operation
If concurrency is relevant, read up on proper UPSERT solutions.
How to UPSERT (MERGE, INSERT ... ON DUPLICATE UPDATE) in PostgreSQL?
Related
I have multiple statements in a trigger that involves in updating data, the last statement will insert the data in a temporary table but I need the previous statements should be executed first so the data will be inserted is updated. So in this example.
CREATE TRIGGER foo_trigg AFTER UPDATE OF foo_col1 ON foo WHEN NEW.foo_col2 = 2
BEGIN
-- update statement 1;
-- update statement 2;
-- update statement 3;
-- update statement n;
-- insert statement on temporary table;
END
Is the execute order of the statements in the trigger foo_trigg will be always guaranteed to be like this?
update statement 1 -> update statement 2 -> update statement 3 -> update statement n -> insert statement on temporary table
I'm sorry, it just the control flow of sql kinda hard to understand atleast to me.
I have to change from given Oracle trigger:
CREATE OR REPLACE TRIGGER MY_TRIGGER
AFTER UPDATE OF STATUS ON T_TABLE_A
FOR EACH ROW
BEGIN
UPDATE T_TABLE_B T
SET T.STATUS = :NEW.STATUS
WHERE T.REF_ID = :NEW.ID;
END;
/
to an Oracle compound trigger. Effect must be the same. My approach is now:
CREATE OR REPLACE TRIGGER MY_NEW_TRIGGER
for insert or update on T_TABLE_A
compound trigger
before statement -- STUB
is
begin
null;
end before statement;
before each row
is
begin
end before each row;
after each row -- STUB
is
begin
--IDEA: collect ids of changed records (T_TABLE_A) here >> in a global variable? array?
end after each row;
after statement -- STUB
is
begin
--IDEA: Bulk Update of T_TABLE_B (goal is: update T_TABLE_B.STATUS column; must be the same as T_TABLE_A.STATUS)
end after statement;
end;
/
But as a Java Developer I am very slow to find out the correct syntax of variables, arrays and simple DB scriptings, so any approach is helpful.
Approach where to start is marked as "IDEA".
As I can see you have almost done the half of the job , I amended the code to IDEA part.
I have not included the before statement part and also the triggering clause and all you can adjust according to your need. I just considered for updating the status column in my code.
CREATE OR REPLACE TRIGGER my_trigger
FOR UPDATE OF status ON t_table_a
COMPOUND TRIGGER
-- record type to hold each record updated in t_table_a
-- columns we are intersted in are id and status
TYPE table_a_rec IS RECORD(
id t_table_a.id%TYPE
,status t_table_a.status%TYPE);
--table type based on record to access each record using this
TYPE table_a_row_data_t IS TABLE OF table_a_rec INDEX BY PLS_INTEGER;
-- global variable for the compound trigger
g_row_level_data table_a_row_data_t;
AFTER EACH ROW IS
BEGIN
-- IDEA: collect ids of changed records (T_TABLE_A) here >> in a global variable? array?
g_row_level_data(g_row_level_data.count + 1).id := :new.id;
g_row_level_data(g_row_level_data.count).status := :new.status;
END AFTER EACH ROW;
AFTER STATEMENT IS
BEGIN
--IDEA: Bulk Update of T_TABLE_B (goal is: update T_TABLE_B.STATUS column; must be the same as T_TABLE_A.STATUS)
FORALL i IN 1 .. g_row_level_data.count
UPDATE t_table_b t
SET t.status = g_row_level_data(i).status
WHERE t.ref_id = g_row_level_data(i).id;
END AFTER STATEMENT;
END my_trigger;
/
I've created a trigger as follows:
create or replace trigger "PASSENGERS_BACKUP_T1"
after
insert or update or delete on "PASSENGERS"
for each row
begin
if :NEW."P_ID" is NOT null then
INSERT INTO PASSENGERS_BACKUP(
PB_ID,
PB_FIRST_NAME,
PB_LAST_NAME,
PB_STREET_ADDRESS1,
PB_STREET_ADDRESS2,
PB_CITY,
PB_STATE,
PB_POSTAL_CODE,
PB_EMAIL,
PB_PHONE_NUMBER1,
PB_PHONE_NUMBER2,
PB_URL,
PB_CREDIT_LIMIT,
PB_TAGS)
VALUES (
:new.P_ID,
:new.P_FIRST_NAME,
:new.P_LAST_NAME,
:new.P_STREET_ADDRESS1,
:new.P_STREET_ADDRESS2,
:new.P_CITY,
:new.P_STATE,
:new.P_POSTAL_CODE,
:new.P_EMAIL,
:new.PHONE_NUMBER1,
:new.PHONE_NUMBER1,
:new.URL,
:new.CREDIT_LIMIT,
:new.TAGS);
end if;
end;
now, when I update​ an existing row in "passengers" table as per the above trigger another new row is getting added in "passengers_backup" table instead I would like to update the existing row whenever an update is done in "passengers" table rows. As, well If I delete a row in "Passengers" table, if that row exists in 'Passengers_backup' table it should also get deleted. How can I acheive this?
Thanks in advance.
For solving your problem you need to use trigger with corresponding SQL statement for each action: insert, update, delete. As variant you can use something like this (Note, I left only two columns from your example for readability, so modify your trigger as you need):
create or replace trigger "PASSENGERS_BACKUP_TIUD"
after insert or update or delete on "PASSENGER"
for each row
begin
if inserting then
insert into "PASSENGER_BACKUP" (pb_id, pb_first_name)
values (:NEW.pb_id, :NEW.pb_first_name);
elsif updating then
update "PASSENGER_BACKUP"
set pb_id=:NEW.pb_id, pb_first_name=:NEW.pb_first_name
where pb_id=:NEW.pb_id;
elsif deleting then
delete from "PASSENGER_BACKUP"
where pb_id=:OLD.pb_id;
end if;
end;
Also you can see work of this trigger in action on SQL Fiddle.
I can't figure out the correct syntax for the following pseudo-sql:
INSERT INTO some_table
(column1,
column2)
SELECT col1_value,
col2_value
FROM other_table
WHERE ...
RETURNING id
INTO local_var;
I would like to insert something with the values of a subquery.
After inserting I need the new generated id.
Heres what oracle doc says:
Insert Statement
Returning Into
OK i think it is not possible only with the values clause...
Is there an alternative?
You cannot use the RETURNING BULK COLLECT from an INSERT.
This methodology can work with updates and deletes howeveer:
create table test2(aa number)
/
insert into test2(aa)
select level
from dual
connect by level<100
/
set serveroutput on
declare
TYPE t_Numbers IS TABLE OF test2.aa%TYPE
INDEX BY BINARY_INTEGER;
v_Numbers t_Numbers;
v_count number;
begin
update test2
set aa = aa+1
returning aa bulk collect into v_Numbers;
for v_count in 1..v_Numbers.count loop
dbms_output.put_line('v_Numbers := ' || v_Numbers(v_count));
end loop;
end;
You can get it to work with a few extra steps (doing a FORALL INSERT utilizing TREAT)
as described in this article:
returning with insert..select
T
to utilize the example they create and apply it to test2 test table
CREATE or replace TYPE ot AS OBJECT
( aa number);
/
CREATE TYPE ntt AS TABLE OF ot;
/
set serveroutput on
DECLARE
nt_passed_in ntt;
nt_to_return ntt;
FUNCTION pretend_parameter RETURN ntt IS
nt ntt;
BEGIN
SELECT ot(level) BULK COLLECT INTO nt
FROM dual
CONNECT BY level <= 5;
RETURN nt;
END pretend_parameter;
BEGIN
nt_passed_in := pretend_parameter();
FORALL i IN 1 .. nt_passed_in.COUNT
INSERT INTO test2(aa)
VALUES
( TREAT(nt_passed_in(i) AS ot).aa
)
RETURNING ot(aa)
BULK COLLECT INTO nt_to_return;
FOR i IN 1 .. nt_to_return.COUNT LOOP
DBMS_OUTPUT.PUT_LINE(
'Sequence value = [' || TO_CHAR(nt_to_return(i).aa) || ']'
);
END LOOP;
END;
/
Unfortunately that's not possible. RETURNING is only available for INSERT...VALUES statements. See this Oracle forum thread for a discussion of this subject.
You can't, BUT at least in Oracle 19c, you can specify a SELECT subquery inside the VALUES clause and so use RETURNING! This can be a good workaround, even if you may have to repeat the WHERE clause for every field:
INSERT INTO some_table
(column1,
column2)
VALUES((SELECT col1_value FROM other_table WHERE ...),
(SELECT col2_value FROM other_table WHERE ...))
RETURNING id
INTO local_var;
Because the insert is based on a select, Oracle is assuming that you are permitting a multiple-row insert with that syntax. In that case, look at the multiple row version of the returning clause document as it demonstrates that you need to use BULK COLLECT to retrieve the value from all inserted rows into a collection of results.
After all, if your insert query creates two rows - which returned value would it put into an single variable?
EDIT - Turns out this doesn't work as I had thought.... darn it!
This isn't as easy as you may think, and certainly not as easy as it is using MySQL. Oracle doesn't keep track of the last inserts, in a way that you can ping back the result.
You will need to work out some other way of doing this, you can do it using ROWID - but this has its pitfalls.
This link discussed the issue: http://forums.oracle.com/forums/thread.jspa?threadID=352627
I need a query to move a record from one table to another without using multiple statements?
No, you cannot move records in one SQL statement. You have to use an INSERT followed by a DELETE statement. You should wrap these statements into a transaction, to make sure that the copy operation remains atomic.
START TRANSACTION;
INSERT INTO
new_table
SELECT
*
FROM
old_table
WHERE
some_field = 'your_criteria';
DELETE FROM old_table WHERE some_field = 'your_criteria';
COMMIT;
If you really want to do this in a single SQL statement, one way to accomplish this would be to create an "after delete" trigger on the source table that inserts the row into the target table. This way you can move the row from the source table to the target table simply by deleting it from the source table. Of course this will only work if you want to insert into target table for every delete on the source table.
DELIMITER $$
DROP TRIGGER IF EXISTS TR_A_DEL_SOURCE_TABLE $$
CREATE TRIGGER TR_A_DEL_SOURCE_TABLE AFTER DELETE ON SOURCE_TABLE FOR EACH ROW BEGIN
INSERT IGNORE INTO TARGET_TABLE(id,val1,val2) VALUES(old.id,old.va1,old.val2);
END $$
DELIMITER ;
So to move the row with id 42 from source table to target table:
delete from source_table where id = 42;
No - you might be able to do the INSERT in one nested statement, but you still need to remove the record.
There is no way to make it a single query, but if you HAVE to do it in a single query within an application you can create a Stored Procedure to do it for you.
DELIMITER $$
DROP PROCEDURE IF EXISTS `copydelete` $$
CREATE PROCEDURE `copydelete` (id INT)
BEGIN
INSERT INTO New_Table SELECT * from Old_Table WHERE Old_Table.IdField=id;
DELETE FROM Old_Table where IdField=id;
END $$
DELIMITER ;
Then you're new query is just
CALL copydelete(4);
Which will delete WHERE IdField=4;
Please note that the time delay between insert-select and delete can cause you to delete to much.
For a safe route you could use an update field:
update old_table set move_flag=1 where your_criteria
insert into ... select from ... where move_flag = 1
delete from old_table where move_flag=1
Or use a transaction which locks the old_table so no data can be added between insert... select and delete.