How to delete all the records in SQL Server 2008?
To delete all records from a table without deleting the table.
DELETE FROM table_name use with care, there is no undo!
To remove a table
DROP TABLE table_name
from a table?
You can use this if you have no foreign keys to other tables
truncate table TableName
or
delete TableName
if you want all tables
sp_msforeachtable 'delete ?'
Use the DELETE statement
Delete From <TableName>
Eg:
Delete from Student;
I can see the that the others answers shown above are right, but I'll make your life easy.
I even created an example for you. I added some rows and want delete them.
You have to right click on the table and as shown in the figure Script Table a> Delete to> New query Editor widows:
Then another window will open with a script. Delete the line of "where", because you want to delete all rows. Then click Execute.
To make sure you did it right right click over the table and click in "Select Top 1000 rows". Then you can see that the query is empty.
If you want to reset your table, you can do
truncate table TableName
truncate needs privileges, and you can't use it if your table has dependents (another tables that have FK of your table,
For one table
truncate table [table name]
For all tables
EXEC sp_MSforeachtable #command1="truncate table ?"
Delete rows in the Results pane if you want to delete records in the database. If you want to delete all of the rows you can use a Delete query.
Delete from Table_name
delete from TableName
isn't a good practice.
Like in Google BigQuery, it don't let to use delete without "where" clause.
use
truncate table TableName
instead
When the table is very large, it's better to delete table itself with drop table TableName and recreate it, if one has create table query; rather than deleting records one by one, using delete from statement because that can be time consuming.
The statement is DELETE FROM YourDatabaseName.SomeTableName; if you are willing to remove all the records with reasonable permission. But you may see errors in the constraints that you defined for your Foreign Keys. So that you need to change your constraints before removing the records otherwise there is a command for MySQL (which may work for others) to ignore the constraints.
SET foreign_key_checks = 0;
Please be aware that this command will disable your foreign keys constrain check, so this can be dangerous for the relationships you created within your schema.
Related
I have an unusual problem: I need to delete duplicate records from a table in Postgresql. As i have duplicate records so i dont have primary key and unique index in this table. The table conatins like 20million records and it has duplicate records in it. While i am trying the below query it is taking too long time.
'DELETE FROM temp a using temp b where a.recordid=b.recordid and a.ctid < b.ctid;'
So what should be a better approach to handle such huge table with no index in it?
Appreciate for help.
if you have enough empty space, your can copy table without duplicates, then remove old table and rename new table
like this
INSERT INTO new_table
VALUES
SELECT
DISTINCT ON (column)
*
FROM old_table
ORDER BY column ASC
Use COPY TO to dump the table.
Then Unix sort -u to de-duplicate it.
Drop or truncate the table in Postgres, use COPY FROM to read it back in.
Add a primary key column.
I’m trying to drop temporary tables created by Redshift.
I use the following query to find all the temp tables in the cluster:
select name, count(distinct id)
from stv_tbl_perm
where temp = 1
group by 1
The table i'm trying to drop called $stg_inappshourly.
I've tried to drop it in both of the following methods:
drop table $stg_inappshourly
drop table stg_inappshourly
The first one returns a syntax error. The second one drops the actual table.
Any ideas how to drop it?
Solved.
The reason this table kept existing is because its session had an error and it didn't close as expected.
The only way I found to remove this table was rebooting the Redshift instance.
Problem is following: remove all records from one table, and insert them to another.
I have a table that is partitioned by date criteria. To avoid partitioning each record one by one, I'm collecting the data in one table, and periodically move them to another table. Copied records have to be removed from first table. I'm using DELETE query with RETURNING, but the side effect is that autovacuum is having a lot of work to do to clean up the mess from original table.
I'm trying to achieve the same effect (copy and remove records), but without creating additional work for vacuum mechanism.
As I'm removing all rows (by delete without where conditions), I was thinking about TRUNCATE, but it does not support RETURNING clause. Another idea was to somehow configure the table, to automatically remove tuple from page on delete operation, without waiting for vacuum, but I did not found if it is possible.
Can you suggest something, that I could use to solve my problem?
You need to use something like:
--Open your transaction
BEGIN;
--Prevent concurrent writes, but allow concurrent data access
LOCK TABLE table_a IN SHARE MODE;
--Copy the data from table_a to table_b, you can also use CREATE TABLE AS to do this
INSERT INTO table_b AS SELECT * FROM table_a;
--Zeroying table_a
TRUNCATE TABLE table_a;
--Commits and release the lock
COMMIT;
I'm trying to execute an S3 copy operation via Spark-Redshift and I'm looking to modify the Redshift table structure before running the copy command in order to add any missing columns (they should be all VARCHAR).
What I'm able to do is send an SQL query before running the copy, so ideally I would have liked to ALTER TABLE ADD COLUMN IF NOT EXISTS column_name VARCHAR(256). Unfortunately, Redshift does not offer support for ADD COLUMN IF NOT EXISTS, so I'm currently looking for a workaround.
I've tried to query the pg_table_def table to check for the existence of the column, and that works, but I'm not sure how to chain that with an ALTER TABLE statement. Here's the current state of my query, I'm open to any suggestions for accomplishing the above.
select
case when count(*) < 1 then ALTER TABLE tbl { ADD COLUMN 'test_col' VARCHAR(256) }
else 'ok'
end
from pg_table_def where schemaname = 'schema' and tablename = 'tbl' and pg_table_def.column = 'test_col'
Also, I've seen this question: Redshift: add column if not exists, however the accepted answer isn't mentioning how to actually achieve this.
What I would like is when one row of a table is updated and a new table that will duplicate the original table will update as well but the problem is the original table is a master table that depends on other tables. Any idea how to do this? I'm very new to postgresql.
This is what triggers are for, assuming that the source and destination tables are in the same DB. In this case I think you need an AFTER INSERT OR UPDATE OR DELETE trigger.
http://www.postgresql.org/docs/current/static/plpgsql-trigger.html