So as many of you will know, in DB2 you can say
ALTER TABLE EMPLOYEE
ADD CONSTRAINT NEWID UNIQUE(EMPNO,HIREDATE)
Can you say something like
ALTER TABLE EMPLOYEE
ADD CONSTRAINT NEWID UNIQUE(EMPNO,HIREDATE,ACTIVE = 'Y')
I only care about the constraint if the row is active. I looks like you can do this in MSSQL but not DB2... Err, grumble grumble.
It's probably too late for the OP, but I had a similar problem and found the solution here: Emulating partial indexes in DB2
The code for creating a unique index on column empno could look like this:
CREATE UNIQUE INDEX my_index ON employee (CASE WHEN active = 'Y' THEN empno ELSE NULL END) EXCLUDE NULL KEYS;
and accordingly for both columns empno and hiredate:
CREATE UNIQUE INDEX my_index ON employee (CASE WHEN active = 'Y' THEN empno ELSE NULL END, CASE WHEN active = 'Y' THEN hiredate ELSE NULL END) EXCLUDE NULL KEYS;
Unlike several other DBMS, DB2 does not support partial indexes.
So I don't think you will be able to implement this in DB2
Related
I am a beginner in postgresql and databases in general. I have a table with a column product_id. Some of the values in that column are null. I need to change those null values to the values from another table.
I want to do something like this:
insert into a(product_id) (select product_id from b where product_name='foo') where product_id = null;
I realize that this syntax doesn't work but I just need help figuring it out.
Assuming your table name is "a" and you have some null product_id, but the othe colums does contain data.
So you need to UPDATE, not to INSERT.
Your Query will be something like this :
Update a
set product_id = select product_id from b where b.product_name = 'foo'
Where product_id is null
be sure that your sub query (select ..from b) return a unique value.
Try below
INSERT INTO a (product_id)
select product_id from b where product_name='foo';
your where condition is wrong after the) bracket I.e. where product_id = null;
in Amazon Redshift I try to do a bulk insert value in a table from a temp table.
However I only want to insert the values where a compound of values (primary key) not exist in the table, to avoid adding duplicate.
Below the DDL of the table
• clusters_typologies table (table when i want to insert data)
create table if not exists clusters.clusters_typologies
(
cluster_id BIGINT,
typology_id BIGINT,
semantic_id BIGINT,
primary key (cluster_id, typology_id, semantic_id)
);
Temp Table is create with query below and after that all field are correctly inserted.
CREATE TEMPORARY TABLE temporary (
cluster_id bigint,
typology_name varchar(100),
typology_id bigint,
semantic_name varchar(100),
semantic_id bigint
);
Now when i try to insert with that query
INSERT INTO clusters.clusters_typologies (cluster_id, typology_id,semantic_id)
(SELECT temp.cluster_id, temp.typology_id, temp.semantic_id
FROM temporary temp
WHERE NOT EXISTS(SELECT 1
FROM clusters_typologies
where cluster_id = temp.cluster_id
and typology_id = temp.typology_id
and semantic_id = temp.semantic_id));
I got this error and i cannot figured out how to make it work.
Invalid operation: This type of correlated subquery pattern is not supported due to internal error;
Anyone know how to fix or how is the best way to insert in a table with a compound key avoiding duplicate.
Thanks.
To upsert follow this guide
https://docs.aws.amazon.com/redshift/latest/dg/c_best-practices-upsert.html
and note that certain types of correlated subquery are not allowed in redshift - that is the cause of your error
see
https://docs.aws.amazon.com/redshift/latest/dg/r_correlated_subqueries.html
After some attempt I figured out how to do an insert from a temp table, and check from a compound primary key to avoid duplicate.
Basically from AWS documentation that #Jon Scott as sent, I understand that use outer table in inner select is not supported from Redshift.
I solve using a left join and check if the joining column is null.
Below the query I use now.
INSERT INTO clusters.clusters_typologies (cluster_id, typology_id, semantic_id)
(SELECT temp.cluster_id, temp.typology_id, temp.semantic_id
FROM aaaa temp
LEFT JOIN clusters.clusters_typologies clu_typ ON temp.cluster_id = clu_typ.cluster_id AND
temp.typology_id = clu_typ.typology_id AND
temp.semantic_id = clu_typ.semantic_id
WHERE clu_typ.cluster_id IS NULL
AND clu_typ.typology_id IS NULL
AND clu_typ.semantic_id IS NULL);
This is my table :
CREATE TABLE [dbo].[TestTable]
(
[Name1] varchar(50) COLLATE French_CI_AS NOT NULL,
[Name2] varchar(255) COLLATE French_CI_AS NULL,
CONSTRAINT [TestTable_uniqueName1] UNIQUE ([Name1]),
CONSTRAINT [TestTable_uniqueName1Name2] UNIQUE ([Name1], [Name2])
)
ALTER TABLE [dbo].[TestTable]
ADD CONSTRAINT [TestTable_uniqueName1]
UNIQUE NONCLUSTERED ([Name1])
ALTER TABLE [dbo].[TestTable]
ADD CONSTRAINT [TestTable_uniqueName1Name2]
UNIQUE NONCLUSTERED ([Name1], [Name2])
GO
ALTER INDEX [TestTable_uniqueName1]
ON [dbo].[TestTable]
DISABLE
GO
My idea is to enable/disable one or other unique contraint depending on the customer application. With this way, I can catch the thrown exception in my c# code, and display a specific error message to the GUI.
Now, my problem is to alter the collation of columns Name1 & Name2, I need to make them case sensitive (French_CS_AS). To alter these fields, I have to drop the two constraints and recreate it. According to the explained schema, I cannot create an enabled constraint and then disable it, because by some customers, I have duplicate keys for one or other constraint.
For my update script, my idea number 1 was
Save the name of enabled constraints in a temp table
Drop the constraints
Alter columns
Create DISABLED unique constraints
Enable specific constraints according to the saved values in points 1.
My problem is in point 4., I don't find how to create a disabled unique constraint with an ALTER TABLE statement. Is it possible to create it directly in the sys.indexes table ?
My idea number 2 was
Rename TestTable to TestTableCopy
Recreate TestTable with the new fields collation, and otherwise the same schema (indexes, FK, triggers, ...)
Disable specifical unique contraints in TestTable
Migrate data from TestTableCopy to TestTable
Drop TestTableCopy
In this way, my fear is to loose some links with other tables/dependencies, beceause it is a central table in my database.
Is there any other way to achieve my goal?
If necessary, I can use unique indexes instead of unique constraints.
It looks like it is impossible to create a unique index on a column that already has duplicate values.
So, rather than having a disabled unique index either:
not have an index at all (which is the same as having a disabled index from the query processor point of view),
or create a non-unique index.
For those instanses where your client has unique data create unique index. For those instanses where your client has non-unique data create non-unique index.
CREATE PROCEDURE [dbo].[spUsers_AddUsers]
#Name1 varchar(50) ,
#Name2 varchar(50) ,
#Unique bit
AS
declare #err int
begin tran
if #Unique = 1 begin
if not exists (SELECT * FROM Users WHERE Name1 = #Name1 and Name2 = #Name2)
begin
INSERT INTO Users (Name1,Name2)
VALUES (#Name1,#Name2)
set #err = ##ERROR
end else
begin
UPDATE Users
set Name1 = #Name1,
Name2 = #Name2
where Name1 = #Name1 and Name2 = #Name2
set #err = ##ERROR
end
end else begin
if not exists ( SELECT * FROM Users WHERE Name1 = #Name1 )
begin
INSERT INTO Users (Name1,Name2)
VALUES (#Name1,#Name2)
set #err = ##ERROR
end else
begin
UPDATE Users
set Name1 = #Name1,
Name2 = #Name2
where Name1 = #Name1
set #err = ##ERROR
end
if #err = 0 commit tran
else rollback tran
So first you check if you need an unique Name1 and Name2 or just Name1. Then if you do you an insert/update based on what constrain you have.
I have a table called users_import into which I am parsing and importing a CSV file. Using that table I want to UPDATE my users table if the user already exists, or INSERT if it does not already exist. (This is actually a very simplified example of something much more complicated I'm trying to do.)
I am trying to do something very similar to this:
https://stackoverflow.com/a/8702291/912717
Here are the table definitions and query:
CREATE TABLE users (
id INTEGER NOT NULL UNIQUE PRIMARY KEY,
name TEXT NOT NULL
);
CREATE TABLE users_import (
id INTEGER NOT NULL UNIQUE PRIMARY KEY,
name TEXT NOT NULL
);
WITH upsert AS (
UPDATE users AS u
SET
name = i.name
FROM users_import AS i
WHERE u.id = i.id
RETURNING *
)
INSERT INTO users (name)
SELECT id, name
FROM users_import
WHERE NOT EXISTS (SELECT 1 FROM upsert WHERE upsert.id = users_import.id);
That query gives this error:
psql:test.sql:23: ERROR: column reference "id" is ambiguous
LINE 11: WHERE NOT EXISTS (SELECT 1 FROM upsert WHERE upsert.id = us...
^
Why is id ambiguous and what is causing it?
The RETURNING * in the WITH upsert... clause has all columns from users and all columns from the joined table users_import. So the result has two columns named id and two columns named name, hence the ambiguity when refering to upsert.id.
To avoid that, use RETURNING u.id if you don't need the rest of the columns.
I'm using PostgreSQL 9.0 and I have a table with just an artificial key (auto-incrementing sequence) and another unique key. (Yes, there is a reason for this table. :)) I want to look up an ID by the other key or, if it doesn't exist, insert it:
SELECT id
FROM mytable
WHERE other_key = 'SOMETHING'
Then, if no match:
INSERT INTO mytable (other_key)
VALUES ('SOMETHING')
RETURNING id
The question: is it possible to save a round-trip to the DB by doing both of these in one statement? I can insert the row if it doesn't exist like this:
INSERT INTO mytable (other_key)
SELECT 'SOMETHING'
WHERE NOT EXISTS (SELECT * FROM mytable WHERE other_key = 'SOMETHING')
RETURNING id
... but that doesn't give the ID of an existing row. Any ideas? There is a unique constraint on other_key, if that helps.
Have you tried to union it?
Edit - this requires Postgres 9.1:
create table mytable (id serial primary key, other_key varchar not null unique);
WITH new_row AS (
INSERT INTO mytable (other_key)
SELECT 'SOMETHING'
WHERE NOT EXISTS (SELECT * FROM mytable WHERE other_key = 'SOMETHING')
RETURNING *
)
SELECT * FROM new_row
UNION
SELECT * FROM mytable WHERE other_key = 'SOMETHING';
results in:
id | other_key
----+-----------
1 | SOMETHING
(1 row)
No, there is no special SQL syntax that allows you to do select or insert. You can do what Ilia mentions and create a sproc, which means it will not do a round trip fromt he client to server, but it will still result in two queries (three actually, if you count the sproc itself).
using 9.5 i successfully tried this
based on Denis de Bernardy's answer
only 1 parameter
no union
no stored procedure
atomic, thus no concurrency problems (i think...)
The Query:
WITH neworexisting AS (
INSERT INTO mytable(other_key) VALUES('hello 2')
ON CONFLICT(other_key) DO UPDATE SET existed=true -- need some update to return sth
RETURNING *
)
SELECT * FROM neworexisting
first call:
id|other_key|created |existed|
--|---------|-------------------|-------|
6|hello 1 |2019-09-11 11:39:29|false |
second call:
id|other_key|created |existed|
--|---------|-------------------|-------|
6|hello 1 |2019-09-11 11:39:29|true |
First create your table ;-)
CREATE TABLE mytable (
id serial NOT NULL,
other_key text NOT NULL,
created timestamptz NOT NULL DEFAULT now(),
existed bool NOT NULL DEFAULT false,
CONSTRAINT mytable_pk PRIMARY KEY (id),
CONSTRAINT mytable_uniq UNIQUE (other_key) --needed for on conflict
);
you can use a stored procedure
IF (SELECT id FROM mytable WHERE other_key = 'SOMETHING' LIMIT 1) < 0 THEN
INSERT INTO mytable (other_key) VALUES ('SOMETHING')
END IF
I have an alternative to Denis answer, that I think is less database-intensive, although a bit more complex:
create table mytable (id serial primary key, other_key varchar not null unique);
WITH table_sel AS (
SELECT id
FROM mytable
WHERE other_key = 'test'
UNION
SELECT NULL AS id
ORDER BY id NULLS LAST
LIMIT 1
), table_ins AS (
INSERT INTO mytable (id, other_key)
SELECT
COALESCE(id, NEXTVAL('mytable_id_seq'::REGCLASS)),
'test'
FROM table_sel
ON CONFLICT (id) DO NOTHING
RETURNING id
)
SELECT * FROM table_ins
UNION ALL
SELECT * FROM table_sel
WHERE id IS NOT NULL;
In table_sel CTE I'm looking for the right row. If I don't find it, I assure that table_sel returns at least one row, with a union with a SELECT NULL.
In table_ins CTE I try to insert the same row I was looking for earlier. COALESCE(id, NEXTVAL('mytable_id_seq'::REGCLASS)) is saying: id could be defined, if so, use it; whereas if id is null, increment the sequence on id and use this new value to insert a row. The ON CONFLICT clause assure
that if id is already in mytable I don't insert anything.
At the end I put everything together with a UNION between table_ins and table_sel, so that I'm sure to take my sweet id value and execute both CTE.
This query needs to search for the value other_key only once, and is a "search this value" not a "check if this value not exists in the table", that is very heavy; in Denis alternative you use other_key in both types of searches. In my query you "check if a value not exists" only on id that is a integer primary key, that, for construction, is fast.
Minor tweak a decade late to Denis's excellent answer:
-- Create the table with a unique constraint
CREATE TABLE mytable (
id serial PRIMARY KEY
, other_key varchar NOT NULL UNIQUE
);
WITH new_row AS (
-- Only insert when we don't find anything, avoiding a table lock if
-- possible.
INSERT INTO mytable ( other_key )
SELECT 'SOMETHING'
WHERE NOT EXISTS (
SELECT *
FROM mytable
WHERE other_key = 'SOMETHING'
)
RETURNING *
)
(
-- This comes first in the UNION ALL since it'll almost certainly be
-- in the query cache. Marginally slower for the insert case, but also
-- marginally faster for the much more common read-only case.
SELECT *
FROM mytable
WHERE other_key = 'SOMETHING'
-- Don't check for duplicates to be removed
UNION ALL
-- If we reach this point in iteration, we needed to do the INSERT and
-- lock after all.
SELECT *
FROM new_row
) LIMIT 1 -- Just return whatever comes first in the results and allow
-- the query engine to cut processing short for the INSERT
-- calculation.
;
The UNION ALL tells the planner it doesn't have to collect results for de-duplication. The LIMIT 1 at the end allows the planner to short-circuit further processing/iteration once it knows there's an answer available.
NOTE: There is a race condition present here and in the original answer. If the entry does not already exist, the INSERT will fail with a unique constraint violation. The error can be suppressed with ON CONFLICT DO NOTHING, but the query will return an empty set instead of the new row. This is a difficult problem because getting that info from another transaction would violate the I in ACID.