I have a table that has 60 million rows of data. I would like to introduce a new column say "id" for the table that is an auto incremented sequence.
For example:
CREATE TABLE Persons (
LastName varchar(255),
FirstName varchar(255)
);
INSERT INTO Persons VALUES ('abc', 'def');
INSERT INTO Persons VALUES ('abcd', 'ghi');
CREATE SEQUENCE "PERSON_SEQUENCE" START WITH 1 INCREMENT BY 1;
ALTER TABLE PERSONS ADD (PERSONID NUMBER);
UPDATE persons SET personid = PERSON_SEQUENCE.NEXTVAL;
In the above sql statements, I am able to create a sequence then alter the table and update it.
Since the amount of data I need to update is large.. I would like to perform this with as much low cost as possible.
I am trying to do so something like this:
ALTER TABLE PERSONS ADD (PERSONID NUMBER DEFAULT(PERSON_SEQUENCE.NEXTVAL));
but the above does not work. Oracle throws me the below error:
Error starting at line :
1 in command - ALTER TABLE PERSONS ADD (PERSONID NUMBER
DEFAULT(PERSON_SEQUENCE.NEXTVAL)) Error report -
ORA-00984: column not allowed here
00984. 00000 - "column not allowed here"
*Cause:
*Action:
However this works:
ALTER TABLE PERSONS ADD (PERSONID NUMBER DEFAULT(0));
Could some one help me with how I can achieve to alter a table (create a new column) and populate the column with a seq id both in a single sql. Thank you!
For a table with 60 million rows, I would not do an add column + insert, but create the table new:
RENAME persons TO persons_old;
CREATE TABLE Persons (
personid number,
LastName varchar(255),
FirstName varchar(255)
);
INSERT INTO persons (personid, lastname, firstname)
SELECT person_sequence.nextval, lastname, firstname
FROM persons_old;
DROP TABLE persons_old;
If this is still taking too long, speak to your DBA about ALTER TABLE NOLOGGING and INSERT /*+ APPEND */ and PARALLEL DML.
EDIT: Ah, yes, for 60 million you could even increase the cache size of the sequence for the initial assignment:
ALTER SEQUENCE PERSON_SEQUENCE CACHE 1000;
This worked for me:
alter table PERSONS add (PERSON_ID number default PERSON_SEQ.nextval);
Related
I just created a table as below in MS SQL
create table Employee
(emp_id smallint not null,
employee_name varchar (30) not null,
salary money not null,
department varchar(30),
address varchar(40),
primary key(emp_id)
)
After creating the table, I feel like auto populating the emp_id column( using Identity). So, I was trying to drop the column emp_id as below:
alter table Employee
drop column emp_id
Even though, I haven't inserted any rows in the table yet, I am getting the error
Msg 5074, Level 16, State 1, Line 1 The object
'PK__Employee__1299A86183CA4FBC' is dependent on column 'emp_id'. Msg
4922, Level 16, State 9, Line 1 ALTER TABLE DROP COLUMN emp_id failed
because one or more objects access this column.
Please help!!!
Something like this can help .
ALTER TABLE Employee
DROP CONSTRAINT PK__Employee__1299A86183CA4FBC;
alter table Employee
drop column emp_id
I solved the problem by executing below query: I need to remove a column and all the entries from that column to free my DB size my initial table structure is as shown below:
CREATE TABLE words(_id,word,synonyms,favorite,history,updDate)
And I wanted the table in below form
CREATE TABLE words(_id,word,favorite,history,updDate)
So I executed below query and it removed "synonyms" column
BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(_id,word,favorite,history,updDate);
INSERT INTO t1_backup SELECT _id,word,favorite,history,updDate FROM words;
DROP TABLE words;
CREATE TABLE words(_id,word,favorite,history,updDate);
INSERT INTO words SELECT _id,word,favorite,history,updDate FROM t1_backup;
DROP TABLE t1_backup
COMMIT;
I beginning to learn how to write trigger with this basic database.
I'm also making my very 1st database.
Schema
Team:
TeamID int PK (TeamID int IDENTITY(0,1) CONSTRAINT TeamID_PK PRIMARY KEY)
TeamName nvarchar(100)
History:
HistoryID int PK (HistoryID int IDENTITY(0,1) CONSTRAINT HistoryID_PK PRIMARY KEY)
TeamID int FK REF Team(TeamID)
WinCount int
LoseCount int
My trigger: when a new team is inserted, it should insert a new history row with that team id
CREATE TRIGGER after_insert_Player
ON Team
FOR INSERT
AS
BEGIN
INSERT INTO History (TeamID, WinCount, LoseCount)
SELECT DISTINCT i.TeamID
FROM Inserted i
LEFT JOIN History h ON h.TeamID = i.TeamID
AND h.WinCount = 0 AND h.LoseCount = 0
END
Executed it returns
The select list for the INSERT statement contains fewer items than the insert list. The number of SELECT values must match the number of INSERT columns.
Please help thank. I'm using SQL Server
The error text is the best guide, it is so clear ..
You try inserting one value from i.TeamID into three columns (TeamID,WinCount,LoseCount)
consider these WinCount and LoseCount while inserting.
Note: I Think the structure of History table need to revisit, you should select WinCount and LoseCount as Expressions not as actual columns.
When you specify insert columns, you say which columns you will be filling. But in your case, right after insert you select only one column (team id).
You either have to modify the insert to contain only one column, or select, to retrieve 3 fields as in insert.
If you mention the columns where values have to be inserted(Using INSERT-SELECT).
The SELECT Statement has to contain the same number of columns that have been specified to be inserted. Also, ensure they are of the same data type.(You might face some issues otherwise)
I had created a new table named USERLOG with two fields from a previous VIEW. The table already consist of about 9000 records. The two fields taken from the VIEW, i.e. weblog_views consist of IP (consists of IP address), and WEB_LINK (consists of URL). This is the code I used,
CREATE TABLE USERLOG
AS
SELECT C_IP, WEB_LINK FROM weblog_views;
I want to add another column to this table called the USER_ID, which would consists of a sequence starting with 1 to 9000 records to create a unique id for each existing rows. I need help with this part. I'm using Oracle SQL Developer: ODMiner version 3.0.04.
I tried using the AUTO-INCREMENT option,
ALTER TABLE USERLOG
ADD USER_ID INT UNSIGNED NOT NULL AUTO_INCREMENT;
But I get an error with this,
Error report:
SQL Error: ORA-01735: invalid ALTER TABLE option
01735. 00000 - "invalid ALTER TABLE option"
So, I would really appreciate any help that I can get!
You would need to add a column
ALTER TABLE userlog
ADD( user_id number );
create a sequence
CREATE SEQUENCE user_id_seq
START WITH 1
INCREMENT BY 1
CACHE 20;
Update the data in the table
UPDATE userlog
SET user_id = user_id_seq.nextval
Assuming that you want user_id to be the primary key, you would then add the primary key constraint
ALTER TABLE userlog
ADD CONSTRAINT pk_user_id PRIMARY KEY( user_id );
If you want to use the sequence to automatically add the user_id when you do an INSERT (the other option would be to specifically reference user_id_seq.nextval in your INSERT statements, you would also need a trigger
CREATE OR REPLACE TRIGGER trg_userlog_user_id
BEFORE INSERT ON userlog
FOR EACH ROW
BEGIN
:new.user_id := user_id_seq.nextval;
END;
In addition to Justin's excellent answer you might want to prevent NULL values for your user_id in the future (as they could still be caused by UPDATE statements). Therefore, execute the following statement at the end:
ALTER TABLE userlog MODIFY(user_id number NOT NULL);
Step 1.
Create sequence to be used by the column
eg:
CREATE SEQUENCE user_id_seq
START WITH 1
INCREMENT BY 1
CACHE 20;
Step 2.
Update new column with sequence
eg:
UPDATE userlog
SET user_id = user_id_seq.nextval;
Step 3. - Set Sequence as the default value for the column, will work only above Oracle 12c
ALTER TABLE USERLOG
MODIFY USER_ID INT DEFAULT user_id_seq.nextval;
I have a table with a column that I want to extract out and put into a separate table.
For example, lets say I have a table named Contacts. Contacts has a column named Name which stores a string. Now I want to pull out the names into another table named Name and link the Contact.Name column to the Id of the Name table.
I can only use SQL to do this. Any ideas on the best way to go about this?
Let me know if I can clarify anything, thanks!
[edit]
One problem is that different contacts can be tied to the same name. So when different contacts have the same name and it gets exported the Name table would only have one unique row for that name and all the contacts would point to that row. I guess this wouldn't make sense if I were actually working on a contact book, but I'm just using it to illustrate my problem.
CREATE TABLE Name (NameID int IDENTITY(1, 1), [Name] varchar(50))
INSERT INTO Name ([Name])
SELECT DISTINCT [Name]
FROM Contact
ALTER TABLE Contact
ADD COLUMN NameID int
UPDATE Contact
SET NameID = [Name].NameID
FROM Contact
INNER JOIN [Name]
ON Contact.[Name] = [Name].[Name]
ALTER TABLE Contact
DROP COLUMN [Name]
Then add foreign key constraint, etc.
Create the new table with a Foreign key that points back to the contact table. Then insert the names and contactids from the contact table into this new table. After that you can drop the "name" column from the contact table.
CREATE TABLE Name
(
ContactId int,
Name nvarchar(100)
);
INSERT Name(Name)
SELECT ContactId, Name From Contact;
ALTER TABLE Contact
DROP Column name;
EDIT: Since you have edited the question to mention that one name can be associated with multiple contacts, this changes things in the opposite way.
CREATE TABLE Name
(
NameId int IDENTITY,
Name nvarchar(100)
);
INSERT Name(Name)
SELECT DISTINCT Name From Contact;
ALTER TABLE Contact
ADD NameId int;
UPDATE c
SET c.NameId = n.NameId
FROM Contact c
JOIN Name n on n.Name = c.Name;
ALTER Table Contact
Drop Column Name;
NOTE: Make sure that you create the appropiate foreign key between the Contact and Name tables using the NameId on the Contact table and also create a UNIQUE constraint on the "name" column in the Name table.
insert into another_table( contact_id, name )
select id, name
from contacts;
insert into new_table (contact_id, name)
select min(id), name
from contacts
group by name;
This is one way of ensuring only one row per name - you can substitute other functions for min (like, for eg max).
I'm not too sure why you would want to do this, though. No matter what, you will end up with some contacts that don't have a name linked to them...
ALTER TABLE `Contacts` ADD `name_id` INT( 12 ) NOT NULL
ALTER TABLE `Name` ADD `Name` VARCHAR( 200 ) NOT NULL
INSERT INTO Name (id, name) SELECT id, Name FROM Contacts
ALTER TABLE `Contacts` DROP `Name`
The problem is the name_id field, which is filles with "0" and should be have the same value as the id in the Contacts-Table. Here you can use the LOOP or ITERATE statement (if you using MySQL).
I've given a client the following query to delete duplicate phone no. records in an MSSQL database, but now they need to also do it on MySQL, and they report that MySQL complains about the format of the query. I've included the setup of a test table with duplicates for my code sample, but the actual delete query is what counts.
I'm asking this in ignorance and urgency, as I am still busy downloading and installing MySQL, and just maybe somebody can help in the mean time.
create table bkPhone
(
phoneNo nvarchar(20),
firstName nvarchar(20),
lastName nvarchar(20)
)
GO
insert bkPhone values('0783313780','Brady','Kelly')
insert bkPhone values('0845319792','Mark','Smith')
insert bkPhone values('0834976958','Bill','Jones')
insert bkPhone values('0845319792','Mark','Smith')
insert bkPhone values('0828329792','Mickey','Mouse')
insert bkPhone values('0834976958','Bill','Jones')
alter table bkPhone add phoneId int identity
delete from bkPhone
where phoneId not in
(
select min(phoneId)
from bkPhone
group by phoneNo,firstName,lastName
having count(*) >= 1
)
Many ways lead to Rome. This is one. It is very fast. So you can use it with big databases. Don't forget the indeces.
The trick is: make phoneNo unique and use "ignore".
drop table if exists bkPhone_template;
create table bkPhone_template (
phoneNo varchar(20),
firstName varchar(20),
lastName varchar(20)
);
insert into bkPhone_template values('0783313780','Brady','Kelly');
insert into bkPhone_template values('0845319792','Mark','Smith');
insert into bkPhone_template values('0834976958','Bill','Jones');
insert into bkPhone_template values('0845319792','Mark','Smith');
insert into bkPhone_template values('0828329792','Mickey','Mouse');
insert into bkPhone_template values('0834976958','Bill','Jones');
drop table if exists bkPhone;
create table bkPhone like bkPhone_template;
alter table bkPhone add unique (phoneNo);
insert ignore into bkPhone (phoneNo,firstName,lastName) select phoneNo,firstName,lastName from bkPhone_template;
drop table bkPhone_template;
If the data table already exists, then you only have to run a create table select with a following insert ignore select. At the end you have to run some table renaming statements. That's all.
This workaround is much,much faster then a delete operation.
You can select out the unique ones by:
select distinct(phoneNo) from bkPhone
and put them into another table, delete the old table and rename the new one to the old name.
MySQL complains, because it makes no sense. You trying to aggregate using min() column by which you group.
Now, if you're trying to delete duplicate phone numbers for the same person, the SQL should be:
delete from bkPhone
where phoneId not in
(
select min(phoneId)
from bkPhone
group by firstName,lastName /* i.e. grouping by person and NOT grouping by phoneId */
having count(*) >= 1
)
Mysql also included:
http://mssql-to-postgresql.blogspot.com/2007/12/deleting-duplicates-in-postgresql-ms.html