I am writing some sql in Postgres to update an audit table. My sql will update the table being audited based on some criteria and then select that updated record to update information in an audit table. This is what I have so far:
DO $$
DECLARE
jsonValue json;
revId int;
template RECORD;
BEGIN
jsonValue = '...Some JSON...'
UPDATE projectTemplate set json = jsonValue where type='InstallationProject' AND account_id IS NULL;
template := (SELECT pt FROM ProjectTemplate pt WHERE pt.type='InstallationProject' AND pt.account_id IS NULL);
IF EXISTS (template) THEN
(
revId := nextval('hibernate_sequence');
insert into revisionentity (id, timestamp) values(revId, extract(epoch from CURRENT_TIMESTAMP));
insert into projectTemplate_aud (rev, revtype, id, name, type, category, validfrom, json, account_id)
VALUES (revId, 1, template.id, template.name, template.type, template.category, template.validfrom, jsonValue, template.account_id);
)
END $$;
My understanding is that template will be undefined if there is nothing in the table that matches that query (and there isn't currently). I want to make it so my query will not attempt to update the audit table if template doesn't exist.
What can I do to update this sql to match what I am trying to do?
You cannot use EXISTS like that, it expects a subquery expression. Plus some other issues with your code.
This single SQL DML statement with data-modifying CTEs should replace your DO command properly. And faster, too:
WITH upd AS (
UPDATE ProjectTemplate
SET json = '...Some JSON...'
WHERE type = 'InstallationProject'
AND account_id IS NULL
RETURNING *
)
, ins AS (
INSERT INTO revisionentity (id, timestamp)
SELECT nextval('hibernate_sequence'), extract(epoch FROM CURRENT_TIMESTAMP)
WHERE EXISTS (SELECT FROM upd) -- minimal valid EXISTS expression!
RETURNING id
)
INSERT INTO ProjectTemplate_aud
(rev , revtype, id, name, type, category, validfrom, json, account_id)
SELECT i.id, 1 , u.id, u.name, u.type, u.category, u.validfrom, u.json, u.account_id
FROM upd u, ins i;
Inserts a single row in revisionentity if the UPDATE found any rows.
Inserts as many rows projectTemplate_aud as rows have been updated.
About data-modifying CTEs:
Insert data in 3 tables at a time using Postgres
Aside: I see a mix of CaMeL-case, some underscores, or just lowercased names. Consider legal, lower-case names exclusively (and avoid basic type names as column names). Most importantly, though, be consistent. Related:
Are PostgreSQL column names case-sensitive?
Misnamed field in subquery leads to join
Related
I am looking to insert or update values in an SQLite database (version > 3.35) avoiding multiple queries. upsert along with returning seems promising :
CREATE TABLE phonebook2(
name TEXT PRIMARY KEY,
phonenumber TEXT,
validDate DATE
);
INSERT INTO phonebook2(name,phonenumber,validDate)
VALUES('Alice','704-555-1212','2018-05-08')
ON CONFLICT(name) DO UPDATE SET
phonenumber=excluded.phonenumber,
validDate=excluded.validDate
WHERE excluded.validDate>phonebook2.validDate RETURNING name;
This helps me track names corresponding to inserted/modified rows. How to find rows where phonebook2 values conflict with values upserted in above statement, but no insert or update happened due to where clause?
The RETURNING clause can't be used to get non-affected rows.
What you can do is execute a SELECT statement before the UPSERT:
WITH cte(name, phonenumber, validDate) AS (VALUES
('Alice', '704-555-1212', '2018-05-08'),
('Bob','804-555-1212', '2018-05-09')
)
SELECT *
FROM phonebook2 p
WHERE EXISTS (
SELECT *
FROM cte c
WHERE c.name = p.name AND c.validDate <= p.validDate
);
In the CTE you may include as many tuples as you want
Let's imagine that we have a plpgsql (PostgreSQL 10.7) function where there is a query like
INSERT INTO "myTable"
SELECT * FROM "anotherTable"
INNER JOIN "otherTable"
...
So, this query will insert several rows into myTable. In the next query I want to collect the ids which were inserted with some condition. So, my idea was to do it the following:
INSERT INTO "resultTable" rt
SELECT FROM "myTable"
INNER JOIN ...
WHERE rt."id" >= firstInsertedId;
Now the question: how to find this firstInsertedId?
My solution:
select nextval(''"myTable.myTable_id_seq"'') into firstInsertedId;
if firstInsertedId > 1 then
perform setval(''"myTable.myTable_id_seq"'', (firstInsertedId - 1));
end if;
I don't really like the solution as I don't think that it is good for the performance to generate the id, then go back, then generate it again during the insertion.
Thoughts:
was thinking about inserting the ids into variable array and then find the minimum, but no luck.
was considering to use lastval() function, but it seems that it doesn'
t work for me even though in a very similar implementation in MySQL LAST_INSERT_ID() worked just fine.
Any suggestions?
You can do both things in a single statement using a data modifying common table expression. You don't really need PL/pgSQL for that.
with new_rows as (
INSERT INTO my_table
SELECT *
FROM anotherTable
JOIN "otherTable" ...
returning my_table.id
)
insert into resulttable (new_id)
select id
from new_rows;
Another option would be to store the generate IDs in an array.
declare
l_ids integer[];
begin
....
with new_rows as (
INSERT INTO my_table
SELECT *
FROM anotherTable
JOIN "otherTable" ...
returning my_table.id
)
select array_agg(id)
into l_ids
from new_rows;
....
end;
There is a db2 database with two tables. The first one, table1, has autoincrement column ID. It is the foreign key for the table2.
A am writing an HTML generator for SQL queries. So with some input parameters it generates a query or multiple queries. It is not connected to the database.
What I need is to get that autoincrement field and use it in next queries.
So basically, the scenario is:
insert into table1;
select autogenerated field ID;
insert into table2 using that ID;
insert into table2 using that ID;
...some more similar inserts...
insert into table2 using that ID;
And all that SQL query should be generated and then used as a single SQL script.
I was thinking about something like this:
SELECT ID FROM FINAL TABLE (INSERT INTO Table1 (t1column1, t1column2, etc.)
VALUES (t1value1, t1value2, etc.))
But I don't know, how I can write the result into a variable so I could use it in next queries like this:
INSERT INTO Table2 (foreignKeyCol, t2column1, t2column2, etc.)
VALUES ($ID, t2value1, t2value2, etc.)
I could just paste that select instead of $ID, but the second query can be used several times with the same $ID and different values.
EDIT: DB2 10.5 on Linux.
You can chain several inserts together using CTEs, like so:
WITH idcte (id) as (
SELECT ID FROM FINAL TABLE (
INSERT INTO Table1 (t1column1, t1column2, etc.)
VALUES (t1value1, t1value2, etc.)
)
),
ins1 (id) as (
SELECT foreignKeyCol FROM FINAL TABLE (
INSERT INTO Table2 (foreignKeyCol, t2column1, t2column2, etc.)
SELECT id, t2value1, t2value2, etc.
FROM idcte
)
),
-- more CTEs
SELECT foreignKeyCol FROM FINAL TABLE (
-- your last INSERT ... SELECT FROM
)
Essentially you will have to wrap each INSERT into a SELECT FROM FINAL TABLE for this to work.
Alternatively, you can use a global variable to keep the ID value:
CREATE VARIABLE myNewId INT;
SET myNewId = (SELECT ID FROM FINAL TABLE (
INSERT INTO Table1 (t1column1, t1column2, etc.)
VALUES (t1value1, t1value2, etc.)
));
INSERT INTO Table2 (foreignKeyCol, t2column1, t2column2, etc.)
VALUES (myNewId, t2value1, t2value2, etc.);
DROP VARIABLE myNewId;
This assumes a recent version of Db2 for LUW.
CREATE TABLE object (
object_id serial,
object_attribute_1 integer,
object_attribute_2 VARCHAR(255)
)
-- primary key object_id
-- btree index on object_attribute_1, object_attribute_2
Here is what I currently have:
SELECT * FROM object
WHERE (object_attribute_1=100 AND object_attribute_2='Some String') OR
(object_attribute_1=200 AND object_attribute_2='Some other String') OR
(..another row..) OR
(..another row..)
When the query returns, I check for what is missing (thus, does not exist in the database).
Then I will make an multiple row insert:
INSERT INTO object (object_attribute_1, object_attribute_2)
VALUES (info, info), (info, info),(info, info)
Then I will select what I just inserted
SELECT ... WHERE (condition) OR (condition) OR ...
And at last, I will merge the two selects on the client side.
Is there a way that I can combine these 3 queries, into one single queries, where I will provide all the data, and INSERT if the records do not already exist and then do a SELECT in the end.
Your suspicion was well founded. Do it all in a single statement using a data-modifying CTE (Postgres 9.1+):
WITH list(object_attribute_1, object_attribute_2) AS (
VALUES
(100, 'Some String')
, (200, 'Some other String')
, .....
)
, ins AS (
INSERT INTO object (object_attribute_1, object_attribute_2)
SELECT l.*
FROM list l
LEFT JOIN object o1 USING (object_attribute_1, object_attribute_2)
WHERE o1.object_attribute_1 IS NULL
RETURNING *
)
SELECT * FROM ins -- newly inserted rows
UNION ALL -- append pre-existing rows
SELECT o.*
FROM list l
JOIN object o USING (object_attribute_1, object_attribute_2);
Note, there is a tiny time frame for a race condition. So this might break if many clients try it at the same time. If you are working under heavy concurrent load, consider this related answer, in particular the part on locking or serializable transaction isolation:
Postgresql batch insert or ignore
I Can't run this query with SQLite
if 0<(select COUNT(*) from Repetition where (Word='behnam' and Topic='mine'))
begin
update Repetition set Counts=1+ (select Counts from Repetition where (Word='behnam' and Topic='mine'))
end
else
begin
insert Repetition(Word,Topic,Counts)values('behnam','mine',1)
end
It says "Syntax error near IF"
How can I solve the problem
SQLite does not have an IF statement (see the list of supported queries)
Insetad, check out out ERIC B's suggestion on another thread. You're effectively looking at doing an UPSERT (UPdate if the record exists, INSERT if not). Eric B. has a good example of how to do this in SQLite syntax utilizing the "INSERT OR REPLACE" functionality in SQLite. Basically, you'd do something like:
INSERT OR REPLACE INTO Repetition (Word, Topic, Counts)
VALUES ( 'behnam', 'mine',
coalesce((select Counts + 1 from Repetition
where Word = 'behnam', AND Topic = 'mine)
,1)
)
Another approach is to INSERT ... SELECT ... WHERE ... EXISTS [or not] (SELECT ...);
I do this sort of thing all the time, and I use jklemmack's suggestion as well. And I do it for other purposes too, such as doing JOINs in UPDATEs (which SQLite3 does not support).
For example:
CREATE TABLE t(id INTEGER PRIMARY KEY, c1 TEXT NOT NULL UNIQUE, c2 TEXT);
CREATE TABLE r(c1 TEXT NOT NULL UNIQUE, c2 TEXT);
INSERT OR REPLACE INTO t (id, c1, c2)
SELECT t.id, coalesce(r.c1, t.c1), coalesce(r.c2, t.c2)
FROM r LEFT OUTER JOIN t ON r.c1 = t.c1
WHERE r.c2 = #param;
The WHERE there has the condition that you'd have in your IF. The JOIN in the SELECT provides the JOIN that SQLite3 doesn't support in UPDATE. The INSERT OR REPLACE and the use of t.id (which can be NULL if the row doesn't exist in t) together provide the THEN and ELSE bodies.
You can apply this over and over. If you'd have three statements (that cannot somehow be merged into one) in the THEN part of the IF you'd need to have three statements with the IF condition in their WHEREs.
This is called an UPSERT (i.e. UPdate or inSERT). It has its forms in almost every type of database. Look at this question for the SQLite version: SQLite - UPSERT *not* INSERT or REPLACE
One way that I've found is based on SQL WHERE clause true/false statement:
SELECT * FROM SOME_TABLE
WHERE
(
SELECT SINGLE_COLUMN_NAME FROM SOME_OTHER_TABLE
WHERE
SOME_COLUMN = 'some value' and
SOME_OTHER_COLUMN = 'some other value'
)
This actually means execute some QUERIES if some other QUERY returns 'any' result.