I have to update around 40 rows in a column of a table with increment of numbers in minus i.e -1,-2,-3,-4 etc in sybase ASE. Can any one tell how to do
Raj, identity values in ASE cannot be set to maintain a sequence of negative values as you want. So that eliminates the simplest approach.
Let's assume your table looks like this:
CREATE TABLE cars (
id not null,
name varchar(20),
serial int null
)
where serial is the column that may contain NULL values.
You could create a trigger on the table to update serial when it is null.
Alternatively if you are trying to update existing values in this table you could run the following code 40 times:
UPDATE cars
SET serial = -(SELECT COUNT(*) FROM cars WHERE serial IS NULL)
WHERE id = (SELECT MAX(id) FROM cars WHERE serial IS NULL)
Of course, for 40 rows manually updating the values sounds attractive!
Related
I have a simple table:
CREATE TABLE [dbo].[Word] (
[WordId] INT IDENTITY (1, 1) NOT NULL,
[NameId] INT NOT NULL
PRIMARY KEY CLUSTERED ([WordId] ASC)
);
I have a unique index on NameId
I am trying to update this table and change one column to a random number:
UPDATE Word SET NameId = ROUND(RAND()*2147483647,0)
I realize there is a very very small chance this will not work but it's actually failing every time even though the table has only a very small number of rows the update always fails and says there's a duplicate.
Can anyone tell me what's happening here and also suggest a way to update this table so that there's no duplicate values of NameId created most of the time.
You are updating every NameId with same value, use WHERE statement to update only one row
EDIT: This should do the trick you are looking for, NewId() generates new id for each row
UPDATE Word SET NameId = abs(checksum(NewId()) % 2147483647)
How many rows do you have? It could be a case of the birthday paradox.
Have you tried doing this:
SELECT ROUND(RAND()*2147483647,0) FROM Word
Do the numbers really need to be pseudo-random? You could use row_number() to make them increment.
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
How do I retrieve the ID of an inserted row in SQL?
Users Table:
Column | Type
--------|--------------------------------
ID | * Auto-incrementing primary key
Name |
Age |
Query Sample:
insert into users (Name, Age) values ('charuka',12)
In MySQL:
SELECT LAST_INSERT_ID();
In SQL Server:
SELECT SCOPE_IDENTITY();
In Oracle:
SELECT SEQNAME.CURRVAL FROM DUAL;
In PostgreSQL:
SELECT lastval();
(edited: lastval is any, currval requires a named sequence)
Note: lastval() returns the latest sequence value assigned by your session, independently of what is happening in other sessions.
In SQL Server, you can do (in addition to the other solutions already present):
INSERT INTO dbo.Users(Name, Age)
OUTPUT INSERTED.ID AS 'New User ID'
VALUES('charuka', 12)
The OUTPUT clause is very handy when doing inserts, updates, deletes, and you can return any of the columns - not just the auto-incremented ID column.
Read more about the OUTPUT clause in the SQL Server Books Online.
In Oracle and PostgreSQL you can do this:
INSERT INTO some_table (name, age)
VALUES
('charuka', 12)
RETURNING ID
When doing this through JDBC you can also do that in a cross-DBMS manner (without the need for RETURNING) by calling getGeneratedKeys() after running the INSERT
I had the same need and found this answer ..
This creates a record in the company table (comp), it the grabs the auto ID created on the company table and drops that into a Staff table (staff) so the 2 tables can be linked, MANY staff to ONE company. It works on my SQL 2008 DB, should work on SQL 2005 and above.
===========================
CREATE PROCEDURE [dbo].[InsertNewCompanyAndStaffDetails]
#comp_name varchar(55) = 'Big Company',
#comp_regno nchar(8) = '12345678',
#comp_email nvarchar(50) = 'no1#home.com',
#recID INT OUTPUT
-- The '#recID' is used to hold the Company auto generated ID number that we are about to grab
AS
Begin
SET NOCOUNT ON
DECLARE #tableVar TABLE (tempID INT)
-- The line above is used to create a tempory table to hold the auto generated ID number for later use. It has only one field 'tempID' and its type INT is the same as the '#recID'.
INSERT INTO comp(comp_name, comp_regno, comp_email)
OUTPUT inserted.comp_id INTO #tableVar
-- The 'OUTPUT inserted.' line above is used to grab data out of any field in the record it is creating right now. This data we want is the ID autonumber. So make sure it says the correct field name for your table, mine is 'comp_id'. This is then dropped into the tempory table we created earlier.
VALUES (#comp_name, #comp_regno, #comp_email)
SET #recID = (SELECT tempID FROM #tableVar)
-- The line above is used to search the tempory table we created earlier where the ID we need is saved. Since there is only one record in this tempory table, and only one field, it will only select the ID number you need and drop it into '#recID'. '#recID' now has the ID number you want and you can use it how you want like i have used it below.
INSERT INTO staff(Staff_comp_id)
VALUES (#recID)
End
-- So there you go. I was looking for something like this for ages, with this detailed break down, I hope this helps.
I'd like to create an SQL table that has no more than n rows of data. When a new row is inserted, I'd like the oldest row removed to make space for the new one.
Is there a typical way of handling this within SQLite?
Should manage it with some outside (third-party) code?
Expanding on Alex' answer, and assuming you have an incrementing, non-repeating serial column on table t named serial which can be used to determine the relative age of rows:
CREATE TRIGGER ten_rows_only AFTER INSERT ON t
BEGIN
DELETE FROM t WHERE serial <= (SELECT serial FROM t ORDER BY serial DESC LIMIT 10, 1);
END;
This will do nothing when you have fewer than ten rows, and will DELETE the lowest serial when an INSERT would push you to eleven rows.
UPDATE
Here's a slightly more complicated case, where your table records "age" of row in a column which may contain duplicates, as for example a TIMESTAMP column tracking the insert times.
sqlite> .schema t
CREATE TABLE t (id VARCHAR(1) NOT NULL PRIMARY KEY, ts TIMESTAMP NOT NULL);
CREATE TRIGGER ten_rows_only AFTER INSERT ON t
BEGIN
DELETE FROM t WHERE id IN (SELECT id FROM t ORDER BY ts DESC LIMIT 10, -1);
END;
Here we take for granted that we cannot use id to determine relative age, so we delete everything after the first 10 rows ordered by timestamp. (SQLite imposes an arbitrary order on rows sharing the same ts).
Seems SQLite's support for triggers can suffice: http://www.sqlite.org/lang_createtrigger.html
article on fixed queues in sql: http://www.xaprb.com/blog/2007/01/11/how-to-implement-a-queue-in-sql
should be able to use the same technique to implement "rolling rows"
This would be something like how you would do it. This assumes that my_id_column is auto-incrementing and is the ordering column for the table.
-- handle rolls forward
-- deletes the oldest row
create trigger rollfwd after insert on my_table when (select count() from my_table) > max_table_size
begin
delete from my_table where my_id_column = (select min(my_id_column) from my_table);
end;
-- handle rolls back
-- inserts an empty row at the position before oldest entry
-- assumes all columns option or defaulted
create trigger rollbk after delete on my_table when (select count() from my_table) < max_table_size
begin
insert into my_table (my_id_column) values ((select min(my_id_column) from my_table) - 1);
end;
I have this table which doesn't have a primary key.
I'm going to insert some records in a new table to analyze them and I'm thinking in creating a new primary key with the values from all the available columns.
If this were a programming language like Java I would:
int hash = column1 * 31 + column2 * 31 + column3*31
Or something like that. But this is SQL.
How can I create a primary key from the values of the available columns? It won't work for me to simply mark all the columns as PK, for what I need to do is to compare them with data from other DB table.
My table has 3 numbers and a date.
EDIT What my problem is
I think a bit more of background is needed. I'm sorry for not providing it before.
I have a database ( dm ) that is being updated everyday from another db ( original source ) . It has records form the past two years.
Last month ( july ) the update process got broken and for a month there was no data being updated into the dm.
I manually create a table with the same structure in my Oracle XE, and I copy the records from the original source into my db ( myxe ) I copied only records from July to create a report needed by the end of the month.
Finally on aug 8 the update process got fixed and the records which have been waiting to be migrated by this automatic process got copied into the database ( from originalsource to dm ).
This process does clean up from the original source the data once it is copied ( into dm ).
Everything look fine, but we have just realize that an amount of the records got lost ( about 25% of july )
So, what I want to do is to use my backup ( myxe ) and insert into the database ( dm ) all those records missing.
The problem here are:
They don't have a well defined PK.
They are in separate databases.
So I thought that If I could create a unique pk from both tables which gave the same number I could tell which were missing and insert them.
EDIT 2
So I did the following in my local environment:
select a.* from the_table#PRODUCTION a , the_table b where
a.idle = b.idle and
a.activity = b.activity and
a.finishdate = b.finishdate
Which returns all the rows that are present in both databases ( the .. union? ) I've got 2,000 records.
What I'm going to do next, is delete them all from the target db and then just insert them all s from my db into the target table
I hope I don't get in something worst : - S : -S
The danger of creating a hash value by combining the 3 numbers and the date is that it might not be unique and hence cannot be used safely as a primary key.
Instead I'd recommend using an autoincrementing ID for your primary key.
Just create a surrogate key:
ALTER TABLE mytable ADD pk_col INT
UPDATE mytable
SET pk_col = rownum
ALTER TABLE mytable MODIFY pk_col INT NOT NULL
ALTER TABLE mytable ADD CONSTRAINT pk_mytable_pk_col PRIMARY KEY (pk_col)
or this:
ALTER TABLE mytable ADD pk_col RAW(16)
UPDATE mytable
SET pk_col = SYS_GUID()
ALTER TABLE mytable MODIFY pk_col RAW(16) NOT NULL
ALTER TABLE mytable ADD CONSTRAINT pk_mytable_pk_col PRIMARY KEY (pk_col)
The latter uses GUID's which are unique across databases, but consume more spaces and are much slower to generate (your INSERT's will be slow)
Update:
If you need to create same PRIMARY KEYs on two tables with identical data, use this:
MERGE
INTO mytable v
USING (
SELECT rowid AS rid, rownum AS rn
FROM mytable
ORDER BY
co1l, col2, col3
)
ON (v.rowid = rid)
WHEN MATCHED THEN
UPDATE
SET pk_col = rn
Note that tables should be identical up to a single row (i. e. have same number of rows with same data in them).
Update 2:
For your very problem, you don't need a PK at all.
If you just want to select the records missing in dm, use this one (on dm side)
SELECT *
FROM mytable#myxe
MINUS
SELECT *
FROM mytable
This will return all records that exist in mytable#myxe but not in mytable#dm
Note that it will shrink all duplicates if any.
Assuming that you have ensured uniqueness...you can do almost the same thing in SQL. The only problem will be the conversion of the date to a numeric value so that you can hash it.
Select Table2.SomeFields
FROM Table1 LEFT OUTER JOIN Table2 ON
(Table1.col1 * 31) + (Table1.col2 * 31) + (Table1.col3 * 31) +
((DatePart(year,Table1.date) + DatePart(month,Table1.date) + DatePart(day,Table1.date) )* 31) = Table2.hashedPk
The above query would work for SQL Server, the only difference for Oracle would be in terms of how you handle the date conversion. Moreover, there are other functions for converting dates in SQL Server as well, so this is by no means the only solution.
And, you can combine this with Quassnoi's SET statement to populate the new field as well. Just use the left side of the Join condition logic for the value.
If you're loading your new table with values from the old table, and you then need to join the two tables, you can only "properly" do this if you can uniquely identify each row in the original table. Quassnoi's solution will allow you to do this, IF you can first alter the old table by adding a new column.
If you cannot alter the original table, generating some form of hash code based on the columns of the old table would work -- but, again, only if the hash codes uniquely identify each row. (Oracle has checksum functions, right? If so, use them.)
If hash code uniqueness cannot be guaranteed, you may have to settle for a primary key composed of as many columns are required to ensure uniqueness (e.g. the natural key). If there is no natural key, well, I heard once that Oracle provides a rownum for each row of data, could you use that?