I want to insert or update data to a table. The column "Group" is UNIQUE and the ID of the group should remain constant.
there Is a Fiddle:
http://sqlfiddle.com/#!17/551ea/3
on Insert, everything is okay
also the Update works for "Group" = 'TEST01'
But when I insert a new group and then update, the ID changes (press multiple "Run SQL")
This is my insert query:
INSERT INTO GROUPS ("GROUP", SERVER, PATH, SHARE)
VALUES ('TEST04', 4, 4, 4)
ON CONFLICT("GROUP") DO UPDATE
SET SERVER = 11,
PATH = 11,
SHARE = 11
WHERE GROUPS."GROUP" = 'TEST01'
The ID will be used in other tables, this should only be created once for the first entry.
and this is the general structure:
CREATE SEQUENCE gid START 1;
CREATE TABLE GROUPS (
ID integer NOT NULL DEFAULT nextval('gid') PRIMARY KEY,
"GROUP" VARCHAR NOT NULL UNIQUE,
SERVER integer,
PATH integer,
SHARE integer
);
Look at this fiddle
Each time there is a conflict on insert - the sequence value is discarded and ON UPDATE requests a new value. So initially you start with 1, then you insert 3 tuples so the final value of the sequence would be 3. Then you try to insert a new tuple but there is a conflict - so the value of sequence is now 4. Then you try to insert a new tuple - and it gets a value of 5 for the sequence.
If you continue to run the 2 inserts the sequence will continue to increment. SQLfiddle probably uses persistent connections or some connection pooling which does not properly reset the sequence when rebuilding the schema.
Related
I am stuck on a problem creating a trigger in SQL Server. I have MyTable with the following columns (simplified):
Sn - Identity, not nullable;
SomeId - int, not nullable;
miscellaneous other columns
The Sn column is nothing special, values 1,2...n.
SomeId needs to be 1000 + Sn, i.e. this is what I want the trigger to do on insert.
The problem I am having is a standard trigger fails if I don't include something for SomeId (error is that null is not allowed), if that trigger is using after insert. Maybe I am meant to use instead of insert, but I am having trouble getting that to work correct or find details about it.
The other factor here - I am not even sure if it is possible for what I am trying to do to work. I.e when a new row is being created and SQL Server generates an Sn (Identity column), can a trigger be part of that process and also compute the SomeId value (which needs the Sn value) before inserting?
If not, as a fallback I could either make the SomeId column nullable (not desirable), or always insert 0 into it (and let the trigger fire afterwards to update it), but that would be a bit grim also.
No need for a trigger. Just use a SEQUENCE to generate the ID values instead of an IDENTITY column, eg
create sequence seq_MyTable
start with 1
increment by 1
go
CREATE TABLE MyTable
(
Sn int not null primary key default (next value for seq_MyTable),
SomeID int not null unique default (next value for seq_MyTable) + 1000,
Name VARCHAR(50) NOT NULL
)
insert into MyTable(Name)
values ('A'),('B'),('C')
select * from Mytable
is it Possible to recover from a temporal table?
I defined 2 tables like this:
create table lib.x(
"ID" INTEGER GENERATED ALWAYS AS IDENTITY (
START WITH 1 INCREMENT BY 1
NO MINVALUE NO MAXVALUE
NO CYCLE NO ORDER
CACHE 20
),
char char(1),
row_start TIMESTAMP(12) NOT NULL GENERATED ALWAYS AS ROW BEGIN IMPLICITLY hidden,
row_end TIMESTAMP(12) NOT NULL GENERATED ALWAYS AS ROW END IMPLICITLY hidden,
row_id TIMESTAMP(12) GENERATED ALWAYS AS TRANSACTION START ID IMPLICITLY hidden,
PERIOD SYSTEM_TIME(row_start, row_end)
);
create table lib.x_history like lib.x;
alter TABLE lib.x
ADD VERSIONING USE HISTORY TABLE lib.x_history;
then I did this:
insert into lib.x(char) values('a'), ('b'), ('c');
delete from lib.x where id = 2;
Is it possible to restore the char 'b' with the ID 2?
Yes and no. It is not a system restore, but of course you can query the old state and use it to insert into the regular table. See the section "Querying system-period temporal data" in the Db2 docs.
You would first construct a query to search AS OF. Later, you could use it as input to an insert statement. Thus, you restore the value, but it is treated as deleting the value and inserting it as new.
I have a table that currently has the following structure
id, row1
(null), 232
(null), 4455
(null), 16
I'd like for id to be an auto incrementing primary key, as follows:
id, row1
1, 232
2, 4455
3, 16
I've read the documentation and it looks like the function that I need is AUTO_INCREMENT and that I can edit the table using an ALTER TABLE statement. However, I can't seem to get the syntax quite right. How do I go about doing this? Is it even possible with a pre-existing table?
What you need to do is the following:
create a new sequence:
CREATE SEQUENCE sequence_auto_increment START 1;
create a new table:
create table tab2 as select * from tab1 limit 0;
insert the data:
insert /*+ direct */ into tab2
select NEXTVAL('sequence_auto_increment'),row1 from tab1;
as #Kermit mentioned the best way to do it in Vertica is to recreate the table(once) instead of multiple times, use the direct hint so you skip the WOS storage(much faster)
As for the column constraint that #Nazmul created, i won't use it Vertica doesn't care to much about constraints, you will need to force him to insert what you want and default constraints are not the way.
You need to update your exiting data something like below
UPDATE table
SET id = table2.id
FROM
(
SELECT row1, RANK() OVER (ORDER BY val) as id
FROM t1;
) as table2
where table.primaryKey = table2.primaryKey
Then you do alter your table using below syntax
-- get the value to start sequence at
SELECT MAX(id) FROM t2;
-- create the sequence
CREATE SEQUENCE seq1 START 5;
-- syntax as of 6.1
-- modify the column to add next value for future rows
ALTER TABLE t2 ALTER COLUMN id SET DEFAULT NEXTVAL('seq1');
If you want to use the Auto_Increment feature,
1)Copy data to temp table
2)Recreate the base table with the column using auto increment
3)Copy back the data to for other columns
If you just want the numbers in, refer the other answer by Nazmul
In a database application, I want to insert, update and delete records in a table of database.
Table is as below:
In this table, Ga1_ID is Primary Key.
Suppose, I insert 5 records as show currently.
In second attempt, if I want to insert 5 other records and if any of these new records contains a primary key attribute which is already present in table it show error. Its fine.
But, when I insert new 5 records... how I can verify these new records's primary key value is not present. I mean, how to match or calculate the already present primary key attributes and then insert new records.
What is the best approach to manage this sort of situation ?
use following query in dataadapter:
da=new SqlDataAdapter("select Ga1_ID from table where Ga1_ID=#pkVal",conn);
DataSet=new DataSet();
da.fill(ds);
//pass parameter for #pkVal
da.SelectCommand.Parameters(1).Value = pkValue;
if(ds.Tables[0].Rows.Count>0) //If number of rows >0 then record exists
BEGIN
messagebox.show("Primary key present");
END
Hope its helpful.
Do not check existing records in advance, i.e. do not SELECT and then INSERT. A better (and pretty common) approach is to try to INSERT and handle exceptions, in particular, catch a primary key violation if any and handle it.
Do the insert in a try/catch block, with different handling in case of a primary key violation exception and other sql exception types.
If there was no exception, then job's done, record was inserted.
If you caught a primary key violation exception, then handle it appropriately (your post does not specify what you want to do in this case, and it's completely up to you)
If you want to perform 5 inserts at once and want to make sure they all succeed or else roll back if any of them failed, then do the inserts within a transaction.
you can do a lookup first before inserting.
IF EXISTS (SELECT * FROM tableName WHERE GA1_id=#newId)
BEGIN
UPDATE tableName SET Ga1_docid = #newdocID, GA1_fieldNAme = #newName, Ga1_fieldValue = #newVal where GA1_id=#newId
END
ELSE
BEGIN
INSERT INTO tableName(GA1_ID, Ga1_docid, GA1_fieldNAme Ga1_fieldValue) VALUES (value1,val2,value3,value4)
END
If you're using SQL Server 2012, use a sequence object - CREATE SEQUENCE.
This way you can get the next value using NEXT VALUE FOR.
With an older SQL Server version, you need to create the primary key field as an IDENTITY field and use the SCOPE_IDENTITY function to get the last identity value and then increment it manually.
Normally, you would like to have a surrogate key wich is generally an identity column that will automatically increment when you are inserting rows so that you don't have to care about knowing which id already exists.
However, if you have to manually insert the id there's a few alternatives for that and knowing wich SQL database you are using would help, but in most SQL implementations, you should be able to do something like:
IF NOT EXISTS
IF NOT EXISTS(
SELECT 1
FROM your_table
WHERE Ga1_ID = 1
)
INSERT INTO ...
SELECT WHERE NOT EXISTS
INSERT INTO your_table (col_1, col_2)
SELECT col_1, col_2
FROM (
SELECT 1 AS col_1, 2 AS col_2
UNION ALL
SELECT 3, 4
) q
WHERE NOT EXISTS (
SELECT 1
FROM your_table
WHERE col_1 = q.col_1
)
For MS SQL Server, you can also look at the MERGE statement and for MySQL, you can use the INSERT IGNORE statement.
Is it possible to have a non-primary key to be auto-incremented with every insertion?
For example, I want to have a log, where every log entry has a primary key (for internal use), and a revision number ( a INT value that I want to be auto-incremented).
As a workaround, this could be done with a sequence, yet I believe that sequences are not supported in SQLite.
You can do select max(id)+1 when you do the insertion.
For example:
INSERT INTO Log (id, rev_no, description)
VALUES ((SELECT MAX(id) + 1 FROM log), 'rev_Id', 'some description')
Note that this will fail on an empty table since there won't be a record with id is 0 but you can either add a first dummy entry or change the sql statement to this:
INSERT INTO Log (id, rev_no, description)
VALUES ((SELECT IFNULL(MAX(id), 0) + 1 FROM Log), 'rev_Id', 'some description')
SQLite creates a unique row id (rowid) automatically. This field is usually left out when you use "select * ...", but you can fetch this id by using "select rowid,* ...". Be aware that according to the SQLite documentation, they discourage the use of autoincrement.
create table myTable ( code text, description text );
insert into myTable values ( 'X', 'some descr.' );
select rowid, * from myTable;
:: Result will be;
1|X|some descr.
If you use this id as a foreign key, you can export rowid - AND import the correct value in order to keep data integrity;
insert into myTable values( rowid, code text, description text ) values
( 1894, 'X', 'some descr.' );
You could use a trigger (http://www.sqlite.org/lang_createtrigger.html) that checks the previous highest value and then increments it, or if you are doing your inserts through in a stored procedure, put that same logic in there.
My answer is very similar to Icarus's so I no need to mention it.
You can use Icarus's solution in a more advanced way if needed. Below is an example of seat availiabilty table for a train reservation system.
insert into Availiability (date,trainid,stationid,coach,seatno)
values (
'11-NOV-2013',
12076,
'SRR',
1,
(select max(seatno)+1
from Availiability
where date='11-NOV-2013'
and trainid=12076
and stationid='SRR'
and coach=1)
);
You can use an AFTER INSERT trigger to emulate a sequence in SQLite (but note that numbers might be reused if rows are deleted). This will make your INSERT INTO statement a lot easier.
In the following example, the revision column will be auto-incremented (unless the INSERT INTO statement explicitly provides a value for it, of course):
CREATE TABLE test (
id INTEGER PRIMARY KEY NOT NULL,
revision INTEGER,
description TEXT NOT NULL
);
CREATE TRIGGER auto_increment_trigger
AFTER INSERT ON test
WHEN new.revision IS NULL
BEGIN
UPDATE test
SET revision = (SELECT IFNULL(MAX(revision), 0) + 1 FROM test)
WHERE id = new.id;
END;
Now you can simply insert a new row like this, and the revision column will be auto-incremented:
INSERT INTO test (description) VALUES ('some description');